- Email: [email protected]
Changes in vascular calcification and bone mineral density in calcium supplement users from the Canadian Multi-center Osteoporosis Study (CaMOS)
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Atherosclerosis journal homepage: www.elsevier.com/locate/atherosclerosis
Changes in vascular calcification and bone mineral density in calcium supplement users from the Canadian Multi-center Osteoporosis Study (CaMOS) Maggie Hulberta, Mandy E. Turnerb, Wilma M. Hopmanc,d, Tassos Anastassiadesa,b, Michael A. Adamsb, Rachel M. Holdena,b,∗ a
Department of Medicine, Queen's University, 94 Stuart St, Kingston, ON, K7L 2V6, Canada Department of Biomedical and Molecular Science, Queen's University, 18 Stuart St, Kingston, ON, K7L 3N6, Canada Kingston General Health Research Institute, 76 Stuart St, Kingston Health Sciences Centre, Kingston, ON, K7L 2V7, Canada d Department of Public Health Sciences, Queen's University,62 Fifth Field Company Lane, Kingston, ON, K7L 3L3, Canada b c
HIGHLIGHTS
supplements, used to prevent osteoporosis, have been linked to cardiovascular events. • Calcium using calcium supplements had greater progression of aortic calcification over 5 years. • Females using calcium supplements did not have preserved bone mineral density. • Females • Calcification may contribute to cardiovascular events in calcium supplement users. ARTICLE INFO
ABSTRACT
Keywords: CaMOS Vascular calcification Calcium supplementation
Background and aims: Calcium supplements have been associated with increased cardiovascular events. This study investigates the relationship between calcium supplement use and the 5 year progression of abdominal aorta calcification (AAC) in participants from one center of the Canadian Multi-Centre Osteoporosis Study (CaMOS). Methods: Participants (n = 296; 217 women and 79 men) had lateral spine X-rays and DEXA bone mineral density (BMD) scans (femoral neck, lumbar spine and total hip) taken at two time points within a 5 year interval. AAC was assessed using the Framingham Method. Calcium supplement use was assessed by a facilitated health history questionnaire and medication inventory. Results: AAC significantly increased over 5 years, AAC progression was significantly greater in calcium supplement users, as compared to non-users, overall and in females. The amount of calcium was positively correlated to AAC progression. A multi-variable linear regression model was generated for women only, as there were not enough men for multivariable modelling. Calcium supplement use and amount remained significantly associated with AAC progression after adjustment for age, hypertension, diabetes and smoking history. Change in AAC score was not associated with change in BMD T-Score. In univariate analyses of males, calcium supplement use was associated with a significantly greater BMD loss at the lumbar spine, hip, and femoral neck. Conclusions: Older female calcium supplement users had significantly higher AAC progression over 5 years, but did not have any significant BMD preservation. These results suggest that vascular calcification may contribute to the cardiovascular events observed in calcium supplement users.
1. Introduction Calcium supplements have been widely used in North America to prevent or treat osteoporosis for decades. Approximately 60% of post-
∗
menopausal women in the United States report use of calcium supplements to meet their recommended daily intake goals [1]. Calcium supplements have recently been re-evaluated for their efficacy in bone mineral density preservation as well as their potential for adverse
Corresponding author. 3048C Etherington Hall, Queen's University, Kingston, ON, K7L 3V6, Canada. E-mail address: [email protected] (R.M. Holden).
https://doi.org/10.1016/j.atherosclerosis.2019.12.003 Received 27 August 2019; Received in revised form 17 October 2019; Accepted 6 December 2019 0021-9150/ © 2019 Elsevier B.V. All rights reserved.
Please cite this article as: Maggie Hulbert, et al., Atherosclerosis, https://doi.org/10.1016/j.atherosclerosis.2019.12.003
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effects on cardiovascular health. A 2011 Institute of Medicine review determined that calcium supplements have an important role in skeletal health [2], and that calcium has an anti-resorptive effect on bone in the short term [3,4]. However, calcium supplements have not been shown to have any long-term benefits for bone health, and many studies have found that calcium supplements have no effect on bone loss that accompanies ageing [5–8]. Further, meta-analysis of calcium intake and hip fracture risk in men and women suggested that calcium supplements do not reduce fracture risk long term [9]. Consequently, a 2015 review and meta-analysis of calcium supplements and bone health concluded that calcium supplements may have a negative risk-benefit effect, and should not be used routinely to prevent bone loss [10]. Data supporting a relationship between calcium supplement use and adverse effects on the cardiovascular system have emerged relatively recently, in large part due to controversies in the Women's Health Initiative (WHI) studies. The WHI is a large (N = 64,500), 15-year clinical investigation of strategies for preventative health in post-menopausal women aged 50–70. In 2007, the WHI reported that calcium or vitamin D supplementation did not increase coronary or cerebrovascular risk [11]. However, women in this study were also taking personal (non-protocol) calcium supplements, and the data was subsequently reanalyzed [12]. A 2011 follow-up study and meta-analysis of these data revealed that calcium supplementation, with or without vitamin D, increased the risk of cardiovascular events in women, particularly myocardial infarctions [12]. Since then, several studies have reported a significant relationship between calcium supplement use and increased risk of cardiovascular events in older women [13–16]. However, these conclusions remain controversial because of several contradicting studies which do not find any associated cardiovascular risk with use of calcium supplements reviewed in this journal by Challoumas et al. [17–19]. For example, a 2016 meta-analysis found no association between daily calcium supplementation and cardiovascular events or increased mortality in healthy adults [20]. A Clinical Practice Guideline from the National Osteoporosis [21]and the American Society of Preventive Cardiology, published in 2016, adopted the position that there was moderate-quality evidence that calcium intake from food or supplements (with or without vitamin D) has no relationship, either beneficial or harmful, to cardiovascular risk or mortality. However, it was recommended that calcium intake from food and supplements not exceed the tolerable upper limit of intake which had been defined by the National Academy of Medicne as 2000–2500 mg/day. It is noteworthy that the distinction between dietary calcium and supplemental calcium is not always clearly made in the literature, with one study reporting there to be significant differences between the two. That is, dietary calcium was found to lower the incidence of CVD events, while supplemental calcium was found to elevate this risk [22]. Taken together, further efforts are required to elucidate the relationship between calcium supplement use and cardiovascular risk. Vascular calcification is an age-related process that contributes to atherosclerosis and the subsequent development of many vascular diseases such as peripheral vascular disease, coronary heart diseases, and stroke. This maladaptive mineral handling resulting in deposition of calcium into the vasculature has been proposed as a potential mechanism underlying the association between calcium supplement use and cardiovascular risk. In the 10-year follow-up of the Multi-Ethnic Study of Atherosclerosis (MESA) study, a significant association between calcium supplement use and incident coronary artery calcification (CAC) was identified [23]. The CAC score and the Framingham Score are research tools that have been validated as a surrogate for atherosclerotic disease previously [24,25]. The CAC score measures incident coronary artery calcification on computed tomography, and the Framingham Score measures abdominal aortic calcification (AAC) on lumbar plain film X-rays. Due to this difference in imaging modality, the Framingham score is more widely available, inexpensive, and requires less radiation. The Framingham score is known to increase proportionately with age and inversely with bone mineral density [26],
although its relationship with calcium supplement use has never been studied. Thus, the primary objective of this investigation was to determine the association between calcium supplement use and the 5 year progression of AAC in community-dwelling, male and female participants at the Kingston, Ontario site of the Canadian Multi-Centre Osteoporosis Study (CaMOS). Secondary objectives were to determine the association between changes in bone density and progression of AAC. To the best of our knowledge, this is the first longitudinal and population-based study to address calcium supplement use and progression of aortic calcification whilst also addressing bone density changes over the same time period. 2. Materials and methods 2.1. Study subjects The population for this study was the Kingston Study Centre cohort of the Canadian Multi-centre Osteoporosis Study (CaMOS), a prospective study of community-dwelling adults. Full details regarding the study population, assessments, and procedures have been previously reported [27–29]. Participants were included in the present study if (1) subjects had both lateral spine X-rays (only conducted in participants > 50 years of age) and BMD measurements by dual X-ray absorptiometry (DXA), (2) taken twice at an interval of 5 years and (3) the X-ray was readable for AAC assessment, meaning the X-ray had sufficient width to encompass the entire abdominal aorta and there were no overlying radiopaque structures, such as urogenital lithiasis. One hundred and seven participants had to be excluded due to poor resolution and contrast of lumbar spine images. After applying these inclusion criteria, 296 subjects were eligible. This study was conducted according to the Declaration of Helsinki and was approved by the Queen's University Human Ethics Research Board. Written informed consent was obtained from each patient in the study. 2.2. Abdominal aortic calcification (AAC) measurement - Framingham Method and image reading AAC was assessed visually from lumbar X-rays in the anterior and posterior walls of the abdominal aorta as a proportion of the adjacent vertebrae (L1-L4) using the Framingham method of scoring (Supplementary Fig. 1) [26]. For each vertebra along the posterior or the anterior wall of the abdominal aorta AAC severity scoring was as follows: 0 = no calcification; 1 = lesion length < one-third length of vertebrae; 2 = lesion length between one-third and two-thirds length of vertebrae; 3 = lesion length > two-thirds length of vertebrae. Therefore, the maximum score an individual can achieve is 24, which is calcification > 2/3 length of the area adjacent to each vertebra at both the anterior and posterior wall of the abdominal aorta. The AAC score of each participant at each time point was assessed by one of three readers. The readers were blinded to the subject's identifying information, and were not involved in the subsequent analysis of data. Inter- and intra-observer reliability of this technique are presented in Supplementary Table 1, consistent with previously reported data from this research group [30]. 2.3. Bone mineral density measurements Bone mineral density (BMD) in the AP direction of the lumbar spine (L1–L4), left femoral neck and total hip was measured by dual X-ray absorptiometry (DXA), using a standard clinical approach, as we have described in detail previously [31]. A Hologic QDR 4500 (Marlborough, MA, USA) densitometer was used. Daily machine calibration and weekly quality assurance tests were performed. The densitometer was calibrated at the start of the study and once each year thereafter using the Bona Fide Spine Phantom (BFP, Bio-Imaging Technologies, 2
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Newtown, PA, USA). The precision, expressed as percent coefficient of variation (%CV), ranged between 0.17 and 0.39. Of the commercially available phantoms studied, the BFP exhibited the closest regression to human data.
therapy. Over half of the study population was taking calcium supplements. Calcium supplement users were more likely to be older (67.0 ± 7.1 vs. 65.2 ± 7.3, p < 0.001) and female (83.7% of users vs. 65.3% of nonusers were female, p < 0.01) and were less likely to smoke (47.3% of users smoked vs. 61.1% of non-users, p < 0.001). Calcium supplement users, both males and females, were more likely to be taking vitamin D supplements. Most female participants were post-menopausal (96.8%), and none of the pre-menopausal women (N = 7) were taking calcium supplements.
2.4. Entry questionnaire data and clinical assessment All participants were given a standardized interviewer-administered questionnaire (CaMOS Questionnaire© 1995) upon entry to the CaMOS study [32]. The questionnaire assessed demographics, health, nutrition, lifestyle, as well as a medical history that included common cardiovascular risk factors. Medication and supplement use were assessed by a complete inventory of prescriptions and bottles brought to the interview. Dietary calcium and vitamin D intake was obtained at baseline from the abbreviated semi-quantitative food frequency questionnaire (FFQ) included in the main questionnaire. This FFQ assessed intake of foods considered to be excellent sources of dietary calcium and included milk to drink, milk products and calcium containing foods including canned salmon, broccoli, leafy green vegetables, dried beans or peas, bread (whole wheat and white), and tofu. Vitamin D intake was based on milk and yogurt fortified with vitamin D.
3.3. Effects of calcium supplement use on AAC progression Overall, the AAC score increased by 1.86 ± 3.24 points over 5 years (p < 0.001). There was no difference in baseline AAC score between men and women (Table 1). The absolute change in AAC score was significantly correlated with age and calcium supplement dose. These associations remained significant when examined in females only but not in males. Participants were separated by degree of AAC progression (Table 2). None, moderate and severe progression were defined as an increase in 0, 2–3 or 3 + points over 5 years, respectively. In both males and females, both moderate and severe progression was not associated with a higher AAC score at baseline. Factors associated with progression of AAC over 5 years are presented (Supplementary Table 2). Participants with a history of smoking, hypertension, diabetes, or calcium supplement use at study entry had a greater increase in AAC score. In calcium supplement users, the change in AAC score over 5 years was significantly higher as compared to non-users (+2.32 ± 0.28 vs. +1.51 ± 0.28, Table 1 and Fig. 1A). This 5 year trend remained significant when examined in women only (Fig. 1B). Female calcium supplement users were more likely to have progression of AAC over 5 years than male calcium supplement users. Of the women who had moderate progression of AAC, 62% were calcium supplement users and 35% had hypertension (Table 2). Of the women who had severe progression of AAC, 55% were calcium supplement users and 57% had hypertension. In comparison, of the women who had no progression, only 39% were calcium supplement users and 28% had hypertension. Women with moderate or severe progression were also older and consumed more total calcium from supplements and food intake as compared to nonusers. In these women, both the amount of dietary calcium consumed and supplement dose were higher than in women with no progression but only the supplement dose was significant (p < 0.01). In a multi-variable logistic regression model conducted in females, factors independently associated with AAC progression included calcium supplement use, age, hypertension and smoking. Diabetes, body mass index (BMI), hormone replacement therapy (HRT), sedentary lifestyle and vitamin D supplements were not significant (Fig. 2). However, very few participants (n = 12) were taking vitamin D supplements without calcium. Amount of calcium use was also significant (p < 0.05), although not included in the same model as the binary use variable. There was no association between progression of AAC overall and BMD or absolute change in BMD at any BMD site or in either sex when examined separately (Supplementary Table 2).
2.5. Statistical analysis All data were analyzed using IBM SPSS software (Version 24 for Windows; Armonk, NY, 2016) and graphs were generated using Graph Pad Prism (Version 7.0b). Inter-rater agreement was assessed using the intra-class correlation. Continuous data were plotted to assess the normality of the underlying distribution, and additionally assessed using the Shapiro-Wilk test. Descriptive statistics (mean and standard deviation or median and interquartile range for continuous data, and frequency with percentage for categorical values) were generated for all variables. The 5 year absolute change of variables (Framingham Score, BMD Scores) was calculated by subtracting the baseline measurement from the measurement taken 5 years later. Differences between calcium supplement users and non-users were examined using the Chi-squared test for categorical variables and independent samples t-tests or the Mann-Whitney U for continuous variables. Differences by 3-level AAC progression (none, moderate, severe) were tested with the one-way ANOVA or the Kruskal-Wallis H. Multivariable logistic regression models were developed for progression in only women, as the sample size was not sufficient for men. Covariates were selected on the basis of a potential association (p < 0.15) in the univariate analyses, and previous literature. A p-value of 0.05 was used as the criteria for statistical significance, and no corrections were made for multiple comparisons. 3. Results 3.1. Inter-rater reliability Intra-class correlations (Supplemental Table 1) indicate a very high degree of reliability between raters, ranging from 0.88 to 0.92. 3.2. Study population characteristics Demographics of the study cohort at entry are presented in Table 1. Of the 296 participants, 217 (73%) were female and the mean age was 65.9 ± 7.3. A high proportion of the study group had a history of smoking (55%), were overweight (41.9%) and had hypertension (38.5%). In contrast, there was a low prevalence of clinical disease, with less than 10% having a history of heart attacks (9.5%), CVA/TIAs (2.7%), or diabetes (5.7%). Approximately one-third of the females in the cohort were taking hormone replacement therapy (36.4%), antiresorptive therapy (36.9%) or supplemental vitamin D (33.3%). None of the male participants were taking anti-resorptive or hormone
3.4. Effects of calcium supplement use on BMD No differences in BMD T-Scores or change in T-Scores at any site (lumbar, hip, femoral neck) was observed based on calcium supplement use overall or when examined in women only (Table 1). However, male calcium supplement users had greater decrease of BMD at all three sites compared to male non-calcium supplement users (Fig. 3). 3
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Table 1a Baseline characteristics of study participants: categorical variables. ALL
Gender Male Female BMI Underweight Normal Overweight Obese Class I Obese Class II Obese Class III Smoking history Heart attack CVA/TIA Hypertension NIDDM Kidney stones Kidney Disease HRT Vitamin D Anti-resorptive therapy Post-menopausal
FEMALE
MALE
All (n = 296)
Calcium supplement non-users (n = 167)
Calcium supplement users (n = 129)
All (n = 217)
Calcium supplement non-users (n = 109)
Calcium supplement users (n = 108)
All (n = 79)
Calcium supplement non-users (n = 58)
Calcium supplement users (n = 21)
79 (26.7) 217 (73.3) 2 (0.7) 83 (28.0) 124 (41.9) 70 (23.6) 14 (4.7) 3 (1.0) 163 (55) 28 (9.5) 8 (2.7) 114 (38.5) 17 (5.7) 16 (5.4) 11 (3.7) 79 (26.7) 84 (28.4) 80 (27.0)
58 (34.7) 109 (65.3) 1 (0.6) 42 (25.1) 73 (43.7) 41 (24.6) 9 (5.4) 1 (0.6) 102 (61.1) 16 (9.6) 3 (1.8) 63 (37.7) 9 (5.4) 9 (5.4) 8 (4.8) 34 (20.4) 12 (7.2) 34 (20.4)
21 (16.3)a 108 (83.7)a 1 (0.8) 41 (31.8) 51 (39.5) 29 (22.5) 5 (3.9) 2 (1.6) 61 (47.3)c 12 (9.4) 5 (3.9) 51 (39.5) 8 (6.2) 7 (5.5) 3 (2.3) 45 (34.9)b 72 (57.6)a 46 (35.7)b
– – 1 (0.5) 69 (31.8) 81 (37.3) 53 (24.4) 10 (4.6) 3 (1.4) 120 (55.3) 15 (6.9) 4 (1.8) 83 (38.2) 16 (7.4) 6 (2.8) 9 (4.2) 79 (36.4) 71 (33.3) 80 (36.9)
– – 0 32 (29.4) 41 (37.6) 30 (27.5) 5 (4.6) 1 (0.9) 68 (62.4) 5 (4.6) 1 (0.9) 39 (35.8) 8 (7.3) 3 (2.8) 7 (6.5) 34 (31.2) 9 (8.3) 34 (31.2)
– – 1 (0.9) 37 (34.3) 40 (37.0) 23 (21.3) 5 (4.6) 2 (1.9) 52 (48.1)c 10 (9.3) 3 (2.8) 44 (40.7) 8 (7.4) 3 (2.8) 2 (1.9) 45 (41.7) 62 (59.6)a 46 (42.6)
– – 1 (1.3) 14 (17.7) 43 (54.4) 17 (21.5) 4 (5.1) 0 (0) 43 (54.4) 13 (16.5) 4 (5.1) 31 (39.2) 1 (1.3) 10 (12.8) 2 (2.5) 0 (0) 13 (16.5) 0 (0)
– – 1 (1.7) 10 (17.2) 32 (55.2) 11 (19.0) 4 (6.9) 0 (0) 34 (58.6) 11 (19.0) 2 (3.5) 24 (41.4) 1 (1.7) 6 (10.3) 1 (1.7) 0 (0) 3 (5.2) 0 (0)
– – 0 (0) 4 (19.0) 11 (52.4) 6 (28.6) 0 (0) 0 (0) 9 (42.9) 2 (9.5) 2 (9.5) 7 (33.3) 0 (0) 4 (20.0) 1 (4.8) 0 (0) 10 (47.6)a 0 (0)
–
–
–
210 (96.8)
102 (93.6)
108 (100.0)b
–
–
–
a
p < 0.001. b p < 0.01. c p < 0.05 in users compared to non-users with Chi Square test. Data presented as N (%). NIDDM: diabetes non-insulin dependent. HRT: hormone replacement therapy.
on AAC change in men or in women. This finding is in line with the literature [33,36,37], and is hypothesized to occur because ingestion of calcium and calcium supplementation have different biological effects on serum calcium. However, common sources of dietary calcium are often foods that promote cardiovascular health, such as leafy greens, legumes, seeds, and dairy products. It is therefore unclear whether the observed effects of dietary calcium are a result of a different biological handling mechanism or an overall healthier diet. The sex-specific differences in vascular calcification observed in our study warrant further investigation. Due to the low number of males in the Kingston CaMOS cohort, it is not possible to conclude that these results could be replicated in a larger, more sex-balanced study. A higher number of males would also be necessary for a multivariate analysis. As well, it is notable that while 97% of the women in this study were post-menopausal, the premenopausal women were not taking calcium supplements (n = 7). While it is difficult to draw any conclusions based on this low number of women, this may indicate that menopause could be a contributing factor to the progression of vascular calcification or alternatively it could indicate that menopausal women are simply more likely to be taking calcium supplements. Given that there are previously reported sex differences in the effects of calcium supplementation on vascular calcification [38] and cardiovascular events [39], it does appear that sex or menopause cannot be ruled out as a factor that influences the calcium supplementation-vascular calcification hypothesis. Both calcium supplement users and non-users lost BMD at all three sites, suggesting that calcium supplementation at this dose may not have a protective effect on BMD. This is consistent with a 2012 study that found a calcium supplement dose below 500 mg/day did not offer any BMD protection to femoral neck or total hip sites in older women [40]. It has been proposed that low-dose calcium supplements are most effective at preventing BMD loss in women with low dietary calcium intake (< 400 mg/day) [41]. As the women in our study had a much higher dietary intake than 400 mg/day and we saw no benefit of calcium supplements on BMD, our data could support this hypothesis. We saw a statistically significant decrease in BMD in male calcium supplement users at all three sites as compared to non-users. The
4. Discussion This longitudinal study investigated the associations between calcium supplement use, change in abdominal aortic calcification and change in bone mineral density over a 5-year period. Women who reported taking calcium supplements at entry had significantly greater AAC progression over a 5-year period than female non-users and males overall. Dietary calcium intake at entry was not associated with change in AAC in women or men. In addition, calcium supplement use at entry had no effect on BMD loss in women, and was associated with greater BMD loss in men. There was no association observed between AAC score change and BMD T-Score change over time in either men or women. The mechanism linking calcium supplementation to adverse cardiac outcomes is currently not well understood. One hypothesis is that excess calcium is deposited into the vasculature as a result of maladaptive mineral handling. In addition to the traditional cardiovascular risk factors such as age, smoking and hypertension, our results suggest calcium supplementation contributes to AAC, the latter of which has been found in a previous study to be correlated to serum calcium [33]. Taken together with the evidence suggesting serum calcium is linked to carotid artery plaque thickness [34] and that AAC predicts adverse cardiovascular outcomes [33,35], these findings may support vascular deposition of calcium as a potential mechanism of poor cardiovascular outcomes in association with calcium supplementation. Given that vascular calcification is a multi-factorial process, it is highly likely that there were other factors aside from calcium supplementation that contributed to the change in AAC in women, although we adjusted for known confounders in our multi-variable model. The women on calcium supplements in our study were on average 3 years older and a greater proportion of them had hypertension, both factors that contribute to increased vascular calcification independent of calcium supplementation. However, calcium supplement users also smoked less than non-users, and had lower AAC at baseline, which could suggest that the calcification seen was not solely due to these well-identified vascular risk factors. It is notable that dietary calcium does not appear to have an effect 4
5
(7.3) (4.9) (2.7) [11.0, 36.7]
(7.3) (4.5) (2.8) [11.8, 36.3]
−0.07 (0.04) −0.07 (0.03) −0.11 (0.03) 0 [0,0] 833.6 (460.5) 0 [0,0] 833.6 (460.5)
0 [0, 200] 1051.7 (577.6)
0 [0, 246] 834.0 (461.9)
1.73 (2.59) 3.24 (3.96) +1.51 (3.21)
65.2 28.2 14.0 19.5
−0.07 (0.57) −0.09 (0.38) −0.11 (0.36)
1.57 (2.32) 3.44 (3.87) +1.86 (3.23)
65.9 28.0 13.8 19.5
Calcium supplement non-users (n = 167) (7.1)c (5.3) (2.6) [9.2, 40.0] (7.0) (4.9) (2.7) [8.7, 35.7]
0 [0, 258] 1051.7 (577.6)
200 [0,400]a 1278.9a (626.2) 334.00 [196.43, 589.45]a 0 [0, 366] 834.7 (465.7) 831.0 (434.6)
−0.11 (0.59) −0.11 (0.40) −0.11 (0.36)
1.53 (2.24) 3.61 (3.97) 2.07 (3.35)
65.8 27.9 13.8 18.8
−0.08 (0.05) −0.17 (0.03) −0.11 (0.03)
1.37 (1.91) 3.69 (3.76) +2.32 (3.22)c
67.0 27.7 13.7 19.5
Calcium supplement users All (n = 217) (n = 129)
FEMALES
(7.0) (4.8) (2.7) [9.1, 36.7]
0 [0,0] 809.7 (420.4)
0 [0,0] 809.7 (420.4)
−0.16 (0.56) −0.12 (0.39) −0.15 (0.36)
1.81 (2.65) 3.35 (4.09) +1.54 (3.34)
64.8 28.0 14.2 19.1
Calcium supplement non-users (n = 109) (7.0)c (5.6) (2.7) [6.8, 34.6]
367 [200, 600] 853.6 (450.0)
200 [0,400]a 1308.0 (611.6)a
−0.6 (0.62) −0.10 (0.41) −0.08 (0.36)
1.26 (1.71) 3.87 (3.84) +2.61 (3.30)c
66.9 27.6 13.5 18.5
Calcium supplement users (n = 108)
0 [0, 43] 842.2 (532.3)
0 [0, 0] 944.2 (582.2)
0.02 (0.49) −0.05 (0.32) −0.10 (0.38)
1.68 (2.54) 2.96 (3.59) 1.28 (2.83)
66.3 (7.8) 28.58 (3.8) 13.8 (2.6) 25.5 [14.2, 38.8]
All (n = 79)
MALES
(7.9) (3.9) (2.8) [13.5 35.3]
0 [0,0] 878.8 (529.2)
0 [0,0] 878.8 (529.2)
+0.09 (0.47) +0.01 (0.31) −0.04 (0.40)
1.29 (2.50) 3.03 (3.74) +1.45 (3.00)
65.9 28.7 13.5 19.9
Calcium supplement non-users (n = 58)
(7.7) (3.6) (1.8) [25.5, 56.9]c
334 [136, 516.] 737.9 (540.9)
0. [0,400.]a 1130.6 (693.5)
−0.18 (0.51)c −0.19 (0.29)c −0.26 (0.24)c
1.95 (2.69) 2.76 (3.24) +0.81 (2.32)
67.4 28.2 14.6 43.8
Calcium supplement users (n = 21)
p < 0.001. b p < 0.01. c p < 0.05 in users compared to nonusers with t-test or Mann-Whitney U. All data presented as mean (SD), except vitamin D, calcium supplements and pack years of smoking presented as median [IQR]. *N = 153 for pack years; 94 for non users and 59 for users; 112 for women (62 for non users and 50 for users) and 41 for men (32 for non users and 9 for users).
a
Age BMI (kg/m2) Sedentary hours per day Pack years* (smokers only) AAC scores Baseline 5 year Absolute change BMD T-Score absolute change Lumbar Total hip Femoral neck Calcium and vitamin D Vitamin D (IU per day) Total calcium: supplements and diet (mg/day) Calcium supplements (mg/day) Dietary only calcium (mg/day)
All (n = 296)
ALL
Table 1b Baseline characteristics of study participants: continuous variables.
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Table 2 3-level AAC progression in women and men. FEMALES
Categorical variables Smoking history Heart attack CVA/TIA Hypertension NIDDM Kidney stones Kidney disease HRT Vitamin D supplement Anti-resorptive therapy Calcium supplement use Continuous variables Age BMI (kg/m2) Sedentary hours per day Pack yearsd (smokers only) AAC scores Baseline 5 year Absolute change Calcium and vitamin D Vitamin D (IU/day) Total calcium: supplements and diet (mg/day) Calcium supplements (mg/day) Dietary calcium (mg/day)
MALES
No progression (N = 100)
Moderate progression (N = 56)
Severe progression (N = 61)
No progression (N = 42)
Moderate progression (N = 21)
Severe progression (N = 16)
52 (52.0) 6 (6.0) 1 (1.0) 28 (28.0)a 5 (5.0) 1 (1.0) 4 (4.0) 38 (38.0) 31 (31.0) 38 (38.0) 39 (39.0)b
29 (51.8) 2 (3.6) 1 (1.8) 20 (35.7)a 4 (7.1) 1 (1.8) 2 (3.6) 19 (33.9) 21 (39.6) 19 (33.9) 35 (62.5)b
39 (63.9) 7 (11.7) 2 (3.3) 35 (57.4)a 7 (11.5) 4 (6.7) 3 (4.9) 22 (36.1) 19 (31.7) 23 (37.7) 34 (55.7)b
21 (100.0) 6 (14.3) 2 (4.9) 14 (33.3) 0 (0) 5 (11.9) 1 (2.4) 0 (0) 6 (14.3) 0 (0) 12 (28.6)
10 (47.6) 4 (19.0) 0 (0) 11 (52.4) 1 (4.8) 3 (15.0) 0 (0) 0 (0) 4 (19.0) 0 (0) 5 (23.8)
12 (75.0) 3 (18.8) 2 (12.5) 6 (37.5) 0 (0) 2 (12.5) 1 (6.3) 0 (0) 3 (18.8) 0 (0) 4 (25.0)
62.9 28.2 14.1 16.8
(6.3)a (5.3) (2.7) [7.0, 36.3]
66.7 28.1 13.8 17.9
(6.0)a (4.5) (2.7) [7.6, 31.6]
69.7 26.8 13.4 22.8
(7.1)a (5.6) (2.6) [9.4, 45.7]
65.8 28.4 13.4 25.5
(7.4)c (3.5) (2.6) [15.5, 42.8]
64.1 28.4 14.6 32.0
(8.0)c (3.7) (2.9) [17.9, 56.9]
70.4 29.3 13.6 15.0
(7.5)c (4.8) (2.4) [6.8, 35.0]
1.36 (2.26) 0.83 (1.80)a −0.53 (1.23)a
1.46 (2.19) 3.34 (2.34)a 1.87 (0.74)a
1.88 (2.24) 8.41 (3.15)a 6.52 (2.46)a
1.71 (2.49) 1.00 (1.81)c −0.71 (1.21)c
1.24 (2.45) 3.05 (2.48)c 1.81 (0.75)c
2.19 (2.83) 8.00 (3.48)c 5.81 (1.87)c
0 [0, 200] 949.3 (538.5)
0 [0, 400] 1159.8 (520.6)
0 [0, 349] 1112.2 (661.5)
0 [0, 0] 909.3 (462.8)
0 [0, 0] 1036.4 (738.2)
0 [0, 0] 918.2 (663.8)
0 [0, 200] 788.0 (412.8)c
162 [0, 321] 954.8 (482.8)c
160 [0, 539] 785.8 (405.9)c
0 [0, 86] 827.6 (448.5)
0 [0, 50] 929.7 (703.3)
0 [0, 24] 770.0 (506.4)
a
p < 0.001. b p < 0.01. c p < 0.05 any progression as compared to no progression. Chi-square test for categorical variables, T-test or Kruskal-Wallis for continuous variables. Categorical data presented at N (%). Continuous variables presented as mean (SD), except vitamin D, calcium supplements and pack years of smoking presented as median [IQR]. *N = 47, 27 and 36 (no, moderate, severe) respectively for women; 21, 12 and 11 for men.
explanation for this observation is not clear, but may be partially related to under-treatment particularly in male participants with low bone densities and osteoporosis as defined by the BMD. The multicenter CaMos cohort is an observational long-term study without clinical interventions by the investigators. However, there is a potential influence of the study design on the frequency of prescribing bone-active agents to study participants over time, since the DXA results were transmitted to the participants and/or their physician, as per ethics requirements for the study. Family physicians then could prescribe agents for low BMD. We found significant “care gaps’ in both women and men in the CaMos study. At baseline (year 1 of the study), 22% of the women who had experienced a fragility fracture were receiving a bisphosphonate and 26% were on hormone therapy (HT). We were not able to differentiate HT use for menopausal symptoms versus osteoporosis. Over a 10-year study period, 42–56% of women with yearly incident clinical fragility fractures were not treated with any osteoporosis medication [42]. Men had a larger care gap and at baseline and year five only 2.3% and 10.3% of men with a clinical fracture reported an osteoporosis
B
Participants (%)
100
Severe AAC Increase
80
Moderate AAC Increase
60
No AAC Progression
40 20 0
Non User
User
Calcium Supplement
5 Year Change in AAC (points)
A
4
Age
p<0.001
Calcium Supplements
p=0.002
Hypertension
p=0.002
BMI
Smoking
p=0.02
Diabetes
p=0.28
Overweight
p=0.36
Obese Class I
p=0.80
Obese Class II/III
p=0.08
HRT
p=0.17
Sedendary Hours
p=0.13
0
5
Odds Ratio ± 95% CI
Fig. 2. Multivariable model of aortic calcification progression in females. Logistic regression model with clinically relevant predictors of AAC progression over 5 years in women. Sedentary hours split at 14.
Calcium Supplement Non-User Calcium Supplement User
*
3 2 1 0
p=0.10
Vitamin D Supplements
Men
6
Women
Fig. 1. Progression of aortic calcification based on calcium supplement use overall and stratified by sex. (A) Participants separated by 5 year change in AAC by either no progression/decrease, moderate progression (1–3), or severe increase greater than 4 points. Calcium supplement users had more progression of AAC (Chi square, p = 0.036). (B) Change in AAC score over 5 years in female and male participants by calcium supplement use. Data presented as mean ± SEM. Two-Way ANOVA with post hoc Sidak-corrected T-tests comparing calcium supplement users to non-users. *p < 0.05.
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A
B
0.2
Calcium Supplement Non-User Calcium Supplement User
0.0
-0.2 -0.4 -0.8
Lumbar
Hip
Males 5 Year Change in BMD T-Score
5 Year Change in BMD T-Score
Female
0.2
0.0
-0.2
*
*
*
-0.4 Lumbar
Neck
BMD Measurement Location
Hip
Neck
BMD Measurement Location
Fig. 3. Bone mineral density changes by calcium supplement use stratified by sex. Change in BMD T-score over 5 years in (A) female and (B) male participants by calcium supplement use. Data presented as mean ± SEM. Users compared to nonusers with T-test. *p < 0.05.
longitudinal and fluctuating calcium supplement use and progression of vascular calcification. In conclusion, calcium supplementation, but not dietary calcium, appears to be related to vascular calcification in older women. As well, calcium supplementation did not provide any protection against BMD loss in older women and was associated with BMD loss in older men. Further studies on the role of calcium supplement-related vascular calcification in comparative groups of men and women are needed. These results suggest that vascular calcification may contribute to the increased cardiovascular events observed in calcium supplement users and support a negative risk-benefit ratio for calcium supplement use.
diagnosis, respectively. At year five, 90% of men with a clinical fragility fracture were still untreated [43]. The male calcium supplement users in this study had similar baseline BMD as non-users however whether these individuals were considered at higher risk for fractures for reasons such as a history of falls, and as such were placed on calcium supplements earlier than their peers is not known. Thus, this result could represent a failure of calcium supplementation for fracture prevention. The ineffectiveness of low dose calcium is supported by a study that found calcium doses under 600 mg/day did not provide any benefit to BMD change in older men [44]. However, due to the small sample size of men in our study, it cannot be concluded that calcium supplementation contributes to BMD loss in men based on this data alone. Notably, change in BMD at any site and change in AAC were not associated with each other in either sex, or overall. Supporting this finding, baseline BMD at any site and baseline AAC were also not significantly correlated with each other in men or in women (data not shown). This is consistent with some [38,45], but not all studies [26,46], indicating that further research is needed to understand the relationship between bone loss and extra-osseous calcification. There are several limitations to this study. Although the CaMOS cohort was randomly sampled, the sampling framework was developed to over-represent older women in this osteoporosis-focused study, resulting in a predominantly female, healthy, Caucasian population, thus restricting the generalizability to other groups. As well, it is important to remember that the presence of vascular calcification on its own is not a clinically significant outcome; further follow up studies on clinical risk are necessary to prove the significance of increases in AAC. As previously mentioned, there is a low number of male calcium supplement users (n = 21), making it difficult to draw conclusions on the sexspecific differences observed. Lastly, there were very few participants taking calcium supplements without Vitamin D. It is therefore not possible to separate the effects of either supplement from the other. A significant limitation of this study is the use of the study entry questionnaire data to establish calcium supplement user status and the absence of data on duration of use prior to the study start. Whilst this information is not available, a US national survey conducted at the same time as the entry questionnaire showed that supplement use was more likely in people who are healthy, older, Caucasian and female, and that this supplement use was likely to have occurred for at least 2 years [47]. This could support the notion that the calcium supplement users in our study were on these supplements for an extended period of time prior to the start, as well as offer a rationale behind the greater AAC increase observed in the female supplement users. Duration of calcium supplement use would be expected to play a significant role in the likelihood of developing vascular calcification. Long-term studies are necessary to resolve the temporal relationship between both
Author contributions The study was conceptualized and conducted by Maggie Hulbert, Tassos Anastassiades, Michael Adams and Rachel Holden. Mandy Turner and Wilma Hopman assisted with the statistical analysis. Declaration of competing interest Maggie Hulbert, Mandy Turner, Wilma Hopman, Tassos Anastassiades, Michael Adams and Rachel Holden declare that they have no conflict of interest. Acknowledgements The Authors acknowledge the Canadian Institutes of Health Research (CIHR) for supporting the collection of all of the data used in this study, through the Canadian Multicenter Osteoporosis Study (CaMos), including the Kingston site. Funding was over a period of approximately 20 years. Appendix A. Supplementary data Supplementary data to this article can be found online at https:// doi.org/10.1016/j.atherosclerosis.2019.12.003. References [1] K.M. Mangano, et al., Calcium intake in the United States from dietary and supplemental sources across adult age groups: new estimates from the National Health and Nutrition Examination Survey 2003-2006, J. Am. Diet. Assoc. 111 (5) (2011) 687–695. [2] H.B. Del Valle, A.L. Yaktine, C.L. Taylor, A.C. Ross, Dietary reference intakes for calcium and vitamin D, in: A.C. Ross, et al. (Ed.), Dietary Reference Intakes for Calcium and Vitamin D, 2011 Washington (DC). [3] I.R. Reid, et al., Long-term effects of calcium supplementation on bone loss and fractures in postmenopausal women: a randomized controlled trial, Am. J. Med. 98
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predictor of cardiovascular events: a meta-analysis, Heart 98 (13) (2012) 988–994. [26] D.P. Kiel, et al., Bone loss and the progression of abdominal aortic calcification over a 25 year period: the Framingham Heart Study, Calcif. Tissue Int. 68 (5) (2001) 271–276. [27] W. Zhou, et al., Longitudinal changes in calcium and vitamin D intakes and relationship to bone mineral density in a prospective population-based study: the Canadian Multicentre Osteoporosis Study (CaMos), J. Musculoskelet. Neuronal Interact. 13 (4) (2013) 470–479. [28] G. Ioannidis, et al., Glucocorticoids predict 10-year fragility fracture risk in a population-based ambulatory cohort of men and women: Canadian Multicentre Osteoporosis Study (CaMos), Arch. Osteoporos. 9 (2014) 169. [29] J.M. Muir, et al., The effect of regular physical activity on bone mineral density in post-menopausal women aged 75 and over: a retrospective analysis from the Canadian multicentre osteoporosis study, BMC Muscoskelet. Disord. 14 (2013) 253. [30] M. Grant, et al., A novel quantitative approach to the measurement of abdominal aortic calcification as applied to the Canadian Multicenter Osteoporosis Study (CaMOS), Bone 97 (2017) 201–208. [31] C. Berger, et al., Peak bone mass from longitudinal data: implications for the prevalence, pathophysiology, and diagnosis of osteoporosis, J. Bone Miner. Res. 25 (9) (2010) 1948–1957. [32] N. Kreiger, et al., Research notes: the Canadian multicentre osteoporosis study (CaMos): background, rationale, methods, Can. J. Aging 18 (3) (1999) 376–387. [33] M.J. Bolland, et al., Abdominal aortic calcification on vertebral morphometry images predicts incident myocardial infarction, J. Bone Miner. Res. 25 (3) (2010) 505–512. [34] M.R. Rubin, et al., Carotid artery plaque thickness is associated with increased serum calcium levels: the Northern Manhattan study, Atherosclerosis 194 (2) (2007) 426–432. [35] J.T. Schousboe, et al., Abdominal aortic calcification detected on lateral spine images from a bone densitometer predicts incident myocardial infarction or stroke in older women, J. Bone Miner. Res. 23 (3) (2008) 409–416. [36] M. Umesawa, et al., Dietary intake of calcium in relation to mortality from cardiovascular disease: the JACC Study, Stroke 37 (1) (2006) 20–26. [37] E.G. Knox, Ischaemic-heart-disease mortality and dietary intake of calcium, Lancet 1 (7818) (1973) 1465–1467. [38] T.K. Wang, et al., Relationships between vascular calcification, calcium metabolism, bone density, and fractures, J. Bone Miner. Res. 25 (12) (2010) 2777–2785. [39] Q. Xiao, et al., Dietary and supplemental calcium intake and cardiovascular disease mortality: the National Institutes of Health-AARP diet and health study, JAMA Intern. Med. 173 (8) (2013) 639–646. [40] K. Nakamura, et al., Effect of low-dose calcium supplements on bone loss in perimenopausal and postmenopausal Asian women: a randomized controlled trial, J. Bone Miner. Res. 27 (11) (2012) 2264–2270. [41] B. Dawson-Hughes, et al., A controlled trial of the effect of calcium supplementation on bone density in postmenopausal women, N. Engl. J. Med. 323 (13) (1990) 878–883. [42] L.A. Fraser, et al., Fragility fractures and the osteoporosis care gap in women: the Canadian Multicentre Osteoporosis Study, Osteoporos. Int. 22 (3) (2011) 789–796. [43] A. Papaioannou, et al., The osteoporosis care gap in men with fragility fractures: the Canadian Multicentre Osteoporosis Study, Osteoporos. Int. 19 (4) (2008) 581–587. [44] I.R. Reid, et al., Randomized controlled trial of calcium supplementation in healthy, nonosteoporotic, older men, Arch. Intern. Med. 168 (20) (2008) 2276–2282. [45] K. Aoyagi, et al., Low bone density is not associated with aortic calcification, Calcif. Tissue Int. 69 (1) (2001) 20–24. [46] M. Naves, et al., Progression of vascular calcifications is associated with greater bone loss and increased bone fractures, Osteoporos. Int. 19 (8) (2008) 1161–1166. [47] K. Radimer, et al., Dietary supplement use by US adults: data from the national health and nutrition examination survey, 1999-2000, Am. J. Epidemiol. 160 (4) (2004) 339–349.
(4) (1995) 331–335. [4] I.R. Reid, et al., Randomized controlled trial of calcium in healthy older women, Am. J. Med. 119 (9) (2006) 777–785. [5] D.J Hosking, et al., Evidence that increased calcium intake does not prevent early postmenopausal bone loss, Clin. Ther. 5 (1998) 933–944 Sep-Oct. [6] I.R. Reid, et al., Determinants of the rate of bone loss in normal postmenopausal women, J. Clin. Endocrinol. Metab. 79 (4) (1994) 950–954. [7] K. Uusi-Rasi, et al., Influence of calcium intake and physical activity on proximal femur bone mass and structure among pre- and postmenopausal women. A 10-year prospective study, Calcif. Tissue Int. 82 (3) (2008) 171–181. [8] K. Nakamura, et al., Nutritional and biochemical parameters associated with 6-year change in bone mineral density in community-dwelling Japanese women aged 69 years and older: the Muramatsu Study, Nutrition 28 (4) (2012) 357–361. [9] H.A. Bischoff-Ferrari, et al., Calcium intake and hip fracture risk in men and women: a meta-analysis of prospective cohort studies and randomized controlled trials, Am. J. Clin. Nutr. 86 (6) (2007) 1780–1790. [10] I.R. Reid, S.M. Bristow, M.J. Bolland, Calcium supplements: benefits and risks, J. Intern. Med. 278 (4) (2015) 354–368. [11] J. Hsia, et al., Calcium/vitamin D supplementation and cardiovascular events, Circulation 115 (7) (2007) 846–854. [12] M.J. Bolland, et al., Calcium supplements with or without vitamin D and risk of cardiovascular events: reanalysis of the Women's Health Initiative limited access dataset and meta-analysis, BMJ 342 (2011) d2040. [13] J.M. Paik, et al., Calcium supplement intake and risk of cardiovascular disease in women, Osteoporos. Int. 25 (8) (2014) 2047–2056. [14] K. Li, et al., Associations of dietary calcium intake and calcium supplementation with myocardial infarction and stroke risk and overall cardiovascular mortality in the Heidelberg cohort of the European Prospective Investigation into Cancer and Nutrition study (EPIC-Heidelberg), Heart 98 (12) (2012) 920–925. [15] K. Michaelsson, et al., Long term calcium intake and rates of all cause and cardiovascular mortality: community based prospective longitudinal cohort study, BMJ 346 (2013) f228. [16] V.A. MoyerU.S.P.S.T, Force*, Vitamin D and calcium supplementation to prevent fractures in adults: U.S. Preventive Services Task Force recommendation statement, Ann. Intern. Med. 158 (9) (2013) 691–696. [17] J.R. Lewis, et al., The effects of calcium supplementation on verified coronary heart disease hospitalization and death in postmenopausal women: a collaborative metaanalysis of randomized controlled trials, J. Bone Miner. Res. 30 (1) (2015) 165–175. [18] R.L. Prentice, et al., Health risks and benefits from calcium and vitamin D supplementation: women's Health Initiative clinical trial and cohort study, Osteoporos. Int. 24 (2) (2013) 567–580. [19] D. Challoumas, C. Cobbold, G. Dimitrakakis, Effects of calcium intake on the cardiovascular system in postmenopausal women, Atherosclerosis 231 (1) (2013) 1–7. [20] M. Chung, et al., Calcium intake and cardiovascular disease risk: an updated systematic review and meta-analysis, Ann. Intern. Med. 165 (12) (2016) 856–866. [21] S.L. Kopecky, et al., Lack of evidence linking calcium with or without vitamin D supplementation to cardiovascular disease in generally healthy adults: a clinical guideline from the national osteoporosis foundation and the American society for preventive Cardiology, Ann. Intern. Med. 165 (12) (2016) 867–868. [22] P.L. Lutsey, E.D. Michos, Vitamin D, calcium, and atherosclerotic risk: evidence from serum levels and supplementation studies, Curr. Atheroscler. Rep. 15 (1) (2013) 293. [23] J.J. Anderson, et al., Calcium intake from diet and supplements and the risk of coronary artery calcification and its progression among older adults: 10-year follow-up of the multi-ethnic study of atherosclerosis (MESA), J Am Heart Assoc 5 (10) (2016). [24] M.J. Blaha, et al., Understanding the utility of zero coronary calcium as a prognostic test: a Bayesian approach, Circ. Cardiovasc. Qual. Outcomes 4 (2) (2011) 253–256. [25] F. Bastos Goncalves, et al., Calcification of the abdominal aorta as an independent
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Contents lists available at ScienceDirect
Atherosclerosis journal homepage: www.elsevier.com/locate/atherosclerosis
Changes in vascular calcification and bone mineral density in calcium supplement users from the Canadian Multi-center Osteoporosis Study (CaMOS) Maggie Hulberta, Mandy E. Turnerb, Wilma M. Hopmanc,d, Tassos Anastassiadesa,b, Michael A. Adamsb, Rachel M. Holdena,b,∗ a
Department of Medicine, Queen's University, 94 Stuart St, Kingston, ON, K7L 2V6, Canada Department of Biomedical and Molecular Science, Queen's University, 18 Stuart St, Kingston, ON, K7L 3N6, Canada Kingston General Health Research Institute, 76 Stuart St, Kingston Health Sciences Centre, Kingston, ON, K7L 2V7, Canada d Department of Public Health Sciences, Queen's University,62 Fifth Field Company Lane, Kingston, ON, K7L 3L3, Canada b c
HIGHLIGHTS
supplements, used to prevent osteoporosis, have been linked to cardiovascular events. • Calcium using calcium supplements had greater progression of aortic calcification over 5 years. • Females using calcium supplements did not have preserved bone mineral density. • Females • Calcification may contribute to cardiovascular events in calcium supplement users. ARTICLE INFO
ABSTRACT
Keywords: CaMOS Vascular calcification Calcium supplementation
Background and aims: Calcium supplements have been associated with increased cardiovascular events. This study investigates the relationship between calcium supplement use and the 5 year progression of abdominal aorta calcification (AAC) in participants from one center of the Canadian Multi-Centre Osteoporosis Study (CaMOS). Methods: Participants (n = 296; 217 women and 79 men) had lateral spine X-rays and DEXA bone mineral density (BMD) scans (femoral neck, lumbar spine and total hip) taken at two time points within a 5 year interval. AAC was assessed using the Framingham Method. Calcium supplement use was assessed by a facilitated health history questionnaire and medication inventory. Results: AAC significantly increased over 5 years, AAC progression was significantly greater in calcium supplement users, as compared to non-users, overall and in females. The amount of calcium was positively correlated to AAC progression. A multi-variable linear regression model was generated for women only, as there were not enough men for multivariable modelling. Calcium supplement use and amount remained significantly associated with AAC progression after adjustment for age, hypertension, diabetes and smoking history. Change in AAC score was not associated with change in BMD T-Score. In univariate analyses of males, calcium supplement use was associated with a significantly greater BMD loss at the lumbar spine, hip, and femoral neck. Conclusions: Older female calcium supplement users had significantly higher AAC progression over 5 years, but did not have any significant BMD preservation. These results suggest that vascular calcification may contribute to the cardiovascular events observed in calcium supplement users.
1. Introduction Calcium supplements have been widely used in North America to prevent or treat osteoporosis for decades. Approximately 60% of post-
∗
menopausal women in the United States report use of calcium supplements to meet their recommended daily intake goals [1]. Calcium supplements have recently been re-evaluated for their efficacy in bone mineral density preservation as well as their potential for adverse
Corresponding author. 3048C Etherington Hall, Queen's University, Kingston, ON, K7L 3V6, Canada. E-mail address: [email protected] (R.M. Holden).
https://doi.org/10.1016/j.atherosclerosis.2019.12.003 Received 27 August 2019; Received in revised form 17 October 2019; Accepted 6 December 2019 0021-9150/ © 2019 Elsevier B.V. All rights reserved.
Please cite this article as: Maggie Hulbert, et al., Atherosclerosis, https://doi.org/10.1016/j.atherosclerosis.2019.12.003
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effects on cardiovascular health. A 2011 Institute of Medicine review determined that calcium supplements have an important role in skeletal health [2], and that calcium has an anti-resorptive effect on bone in the short term [3,4]. However, calcium supplements have not been shown to have any long-term benefits for bone health, and many studies have found that calcium supplements have no effect on bone loss that accompanies ageing [5–8]. Further, meta-analysis of calcium intake and hip fracture risk in men and women suggested that calcium supplements do not reduce fracture risk long term [9]. Consequently, a 2015 review and meta-analysis of calcium supplements and bone health concluded that calcium supplements may have a negative risk-benefit effect, and should not be used routinely to prevent bone loss [10]. Data supporting a relationship between calcium supplement use and adverse effects on the cardiovascular system have emerged relatively recently, in large part due to controversies in the Women's Health Initiative (WHI) studies. The WHI is a large (N = 64,500), 15-year clinical investigation of strategies for preventative health in post-menopausal women aged 50–70. In 2007, the WHI reported that calcium or vitamin D supplementation did not increase coronary or cerebrovascular risk [11]. However, women in this study were also taking personal (non-protocol) calcium supplements, and the data was subsequently reanalyzed [12]. A 2011 follow-up study and meta-analysis of these data revealed that calcium supplementation, with or without vitamin D, increased the risk of cardiovascular events in women, particularly myocardial infarctions [12]. Since then, several studies have reported a significant relationship between calcium supplement use and increased risk of cardiovascular events in older women [13–16]. However, these conclusions remain controversial because of several contradicting studies which do not find any associated cardiovascular risk with use of calcium supplements reviewed in this journal by Challoumas et al. [17–19]. For example, a 2016 meta-analysis found no association between daily calcium supplementation and cardiovascular events or increased mortality in healthy adults [20]. A Clinical Practice Guideline from the National Osteoporosis [21]and the American Society of Preventive Cardiology, published in 2016, adopted the position that there was moderate-quality evidence that calcium intake from food or supplements (with or without vitamin D) has no relationship, either beneficial or harmful, to cardiovascular risk or mortality. However, it was recommended that calcium intake from food and supplements not exceed the tolerable upper limit of intake which had been defined by the National Academy of Medicne as 2000–2500 mg/day. It is noteworthy that the distinction between dietary calcium and supplemental calcium is not always clearly made in the literature, with one study reporting there to be significant differences between the two. That is, dietary calcium was found to lower the incidence of CVD events, while supplemental calcium was found to elevate this risk [22]. Taken together, further efforts are required to elucidate the relationship between calcium supplement use and cardiovascular risk. Vascular calcification is an age-related process that contributes to atherosclerosis and the subsequent development of many vascular diseases such as peripheral vascular disease, coronary heart diseases, and stroke. This maladaptive mineral handling resulting in deposition of calcium into the vasculature has been proposed as a potential mechanism underlying the association between calcium supplement use and cardiovascular risk. In the 10-year follow-up of the Multi-Ethnic Study of Atherosclerosis (MESA) study, a significant association between calcium supplement use and incident coronary artery calcification (CAC) was identified [23]. The CAC score and the Framingham Score are research tools that have been validated as a surrogate for atherosclerotic disease previously [24,25]. The CAC score measures incident coronary artery calcification on computed tomography, and the Framingham Score measures abdominal aortic calcification (AAC) on lumbar plain film X-rays. Due to this difference in imaging modality, the Framingham score is more widely available, inexpensive, and requires less radiation. The Framingham score is known to increase proportionately with age and inversely with bone mineral density [26],
although its relationship with calcium supplement use has never been studied. Thus, the primary objective of this investigation was to determine the association between calcium supplement use and the 5 year progression of AAC in community-dwelling, male and female participants at the Kingston, Ontario site of the Canadian Multi-Centre Osteoporosis Study (CaMOS). Secondary objectives were to determine the association between changes in bone density and progression of AAC. To the best of our knowledge, this is the first longitudinal and population-based study to address calcium supplement use and progression of aortic calcification whilst also addressing bone density changes over the same time period. 2. Materials and methods 2.1. Study subjects The population for this study was the Kingston Study Centre cohort of the Canadian Multi-centre Osteoporosis Study (CaMOS), a prospective study of community-dwelling adults. Full details regarding the study population, assessments, and procedures have been previously reported [27–29]. Participants were included in the present study if (1) subjects had both lateral spine X-rays (only conducted in participants > 50 years of age) and BMD measurements by dual X-ray absorptiometry (DXA), (2) taken twice at an interval of 5 years and (3) the X-ray was readable for AAC assessment, meaning the X-ray had sufficient width to encompass the entire abdominal aorta and there were no overlying radiopaque structures, such as urogenital lithiasis. One hundred and seven participants had to be excluded due to poor resolution and contrast of lumbar spine images. After applying these inclusion criteria, 296 subjects were eligible. This study was conducted according to the Declaration of Helsinki and was approved by the Queen's University Human Ethics Research Board. Written informed consent was obtained from each patient in the study. 2.2. Abdominal aortic calcification (AAC) measurement - Framingham Method and image reading AAC was assessed visually from lumbar X-rays in the anterior and posterior walls of the abdominal aorta as a proportion of the adjacent vertebrae (L1-L4) using the Framingham method of scoring (Supplementary Fig. 1) [26]. For each vertebra along the posterior or the anterior wall of the abdominal aorta AAC severity scoring was as follows: 0 = no calcification; 1 = lesion length < one-third length of vertebrae; 2 = lesion length between one-third and two-thirds length of vertebrae; 3 = lesion length > two-thirds length of vertebrae. Therefore, the maximum score an individual can achieve is 24, which is calcification > 2/3 length of the area adjacent to each vertebra at both the anterior and posterior wall of the abdominal aorta. The AAC score of each participant at each time point was assessed by one of three readers. The readers were blinded to the subject's identifying information, and were not involved in the subsequent analysis of data. Inter- and intra-observer reliability of this technique are presented in Supplementary Table 1, consistent with previously reported data from this research group [30]. 2.3. Bone mineral density measurements Bone mineral density (BMD) in the AP direction of the lumbar spine (L1–L4), left femoral neck and total hip was measured by dual X-ray absorptiometry (DXA), using a standard clinical approach, as we have described in detail previously [31]. A Hologic QDR 4500 (Marlborough, MA, USA) densitometer was used. Daily machine calibration and weekly quality assurance tests were performed. The densitometer was calibrated at the start of the study and once each year thereafter using the Bona Fide Spine Phantom (BFP, Bio-Imaging Technologies, 2
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Newtown, PA, USA). The precision, expressed as percent coefficient of variation (%CV), ranged between 0.17 and 0.39. Of the commercially available phantoms studied, the BFP exhibited the closest regression to human data.
therapy. Over half of the study population was taking calcium supplements. Calcium supplement users were more likely to be older (67.0 ± 7.1 vs. 65.2 ± 7.3, p < 0.001) and female (83.7% of users vs. 65.3% of nonusers were female, p < 0.01) and were less likely to smoke (47.3% of users smoked vs. 61.1% of non-users, p < 0.001). Calcium supplement users, both males and females, were more likely to be taking vitamin D supplements. Most female participants were post-menopausal (96.8%), and none of the pre-menopausal women (N = 7) were taking calcium supplements.
2.4. Entry questionnaire data and clinical assessment All participants were given a standardized interviewer-administered questionnaire (CaMOS Questionnaire© 1995) upon entry to the CaMOS study [32]. The questionnaire assessed demographics, health, nutrition, lifestyle, as well as a medical history that included common cardiovascular risk factors. Medication and supplement use were assessed by a complete inventory of prescriptions and bottles brought to the interview. Dietary calcium and vitamin D intake was obtained at baseline from the abbreviated semi-quantitative food frequency questionnaire (FFQ) included in the main questionnaire. This FFQ assessed intake of foods considered to be excellent sources of dietary calcium and included milk to drink, milk products and calcium containing foods including canned salmon, broccoli, leafy green vegetables, dried beans or peas, bread (whole wheat and white), and tofu. Vitamin D intake was based on milk and yogurt fortified with vitamin D.
3.3. Effects of calcium supplement use on AAC progression Overall, the AAC score increased by 1.86 ± 3.24 points over 5 years (p < 0.001). There was no difference in baseline AAC score between men and women (Table 1). The absolute change in AAC score was significantly correlated with age and calcium supplement dose. These associations remained significant when examined in females only but not in males. Participants were separated by degree of AAC progression (Table 2). None, moderate and severe progression were defined as an increase in 0, 2–3 or 3 + points over 5 years, respectively. In both males and females, both moderate and severe progression was not associated with a higher AAC score at baseline. Factors associated with progression of AAC over 5 years are presented (Supplementary Table 2). Participants with a history of smoking, hypertension, diabetes, or calcium supplement use at study entry had a greater increase in AAC score. In calcium supplement users, the change in AAC score over 5 years was significantly higher as compared to non-users (+2.32 ± 0.28 vs. +1.51 ± 0.28, Table 1 and Fig. 1A). This 5 year trend remained significant when examined in women only (Fig. 1B). Female calcium supplement users were more likely to have progression of AAC over 5 years than male calcium supplement users. Of the women who had moderate progression of AAC, 62% were calcium supplement users and 35% had hypertension (Table 2). Of the women who had severe progression of AAC, 55% were calcium supplement users and 57% had hypertension. In comparison, of the women who had no progression, only 39% were calcium supplement users and 28% had hypertension. Women with moderate or severe progression were also older and consumed more total calcium from supplements and food intake as compared to nonusers. In these women, both the amount of dietary calcium consumed and supplement dose were higher than in women with no progression but only the supplement dose was significant (p < 0.01). In a multi-variable logistic regression model conducted in females, factors independently associated with AAC progression included calcium supplement use, age, hypertension and smoking. Diabetes, body mass index (BMI), hormone replacement therapy (HRT), sedentary lifestyle and vitamin D supplements were not significant (Fig. 2). However, very few participants (n = 12) were taking vitamin D supplements without calcium. Amount of calcium use was also significant (p < 0.05), although not included in the same model as the binary use variable. There was no association between progression of AAC overall and BMD or absolute change in BMD at any BMD site or in either sex when examined separately (Supplementary Table 2).
2.5. Statistical analysis All data were analyzed using IBM SPSS software (Version 24 for Windows; Armonk, NY, 2016) and graphs were generated using Graph Pad Prism (Version 7.0b). Inter-rater agreement was assessed using the intra-class correlation. Continuous data were plotted to assess the normality of the underlying distribution, and additionally assessed using the Shapiro-Wilk test. Descriptive statistics (mean and standard deviation or median and interquartile range for continuous data, and frequency with percentage for categorical values) were generated for all variables. The 5 year absolute change of variables (Framingham Score, BMD Scores) was calculated by subtracting the baseline measurement from the measurement taken 5 years later. Differences between calcium supplement users and non-users were examined using the Chi-squared test for categorical variables and independent samples t-tests or the Mann-Whitney U for continuous variables. Differences by 3-level AAC progression (none, moderate, severe) were tested with the one-way ANOVA or the Kruskal-Wallis H. Multivariable logistic regression models were developed for progression in only women, as the sample size was not sufficient for men. Covariates were selected on the basis of a potential association (p < 0.15) in the univariate analyses, and previous literature. A p-value of 0.05 was used as the criteria for statistical significance, and no corrections were made for multiple comparisons. 3. Results 3.1. Inter-rater reliability Intra-class correlations (Supplemental Table 1) indicate a very high degree of reliability between raters, ranging from 0.88 to 0.92. 3.2. Study population characteristics Demographics of the study cohort at entry are presented in Table 1. Of the 296 participants, 217 (73%) were female and the mean age was 65.9 ± 7.3. A high proportion of the study group had a history of smoking (55%), were overweight (41.9%) and had hypertension (38.5%). In contrast, there was a low prevalence of clinical disease, with less than 10% having a history of heart attacks (9.5%), CVA/TIAs (2.7%), or diabetes (5.7%). Approximately one-third of the females in the cohort were taking hormone replacement therapy (36.4%), antiresorptive therapy (36.9%) or supplemental vitamin D (33.3%). None of the male participants were taking anti-resorptive or hormone
3.4. Effects of calcium supplement use on BMD No differences in BMD T-Scores or change in T-Scores at any site (lumbar, hip, femoral neck) was observed based on calcium supplement use overall or when examined in women only (Table 1). However, male calcium supplement users had greater decrease of BMD at all three sites compared to male non-calcium supplement users (Fig. 3). 3
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Table 1a Baseline characteristics of study participants: categorical variables. ALL
Gender Male Female BMI Underweight Normal Overweight Obese Class I Obese Class II Obese Class III Smoking history Heart attack CVA/TIA Hypertension NIDDM Kidney stones Kidney Disease HRT Vitamin D Anti-resorptive therapy Post-menopausal
FEMALE
MALE
All (n = 296)
Calcium supplement non-users (n = 167)
Calcium supplement users (n = 129)
All (n = 217)
Calcium supplement non-users (n = 109)
Calcium supplement users (n = 108)
All (n = 79)
Calcium supplement non-users (n = 58)
Calcium supplement users (n = 21)
79 (26.7) 217 (73.3) 2 (0.7) 83 (28.0) 124 (41.9) 70 (23.6) 14 (4.7) 3 (1.0) 163 (55) 28 (9.5) 8 (2.7) 114 (38.5) 17 (5.7) 16 (5.4) 11 (3.7) 79 (26.7) 84 (28.4) 80 (27.0)
58 (34.7) 109 (65.3) 1 (0.6) 42 (25.1) 73 (43.7) 41 (24.6) 9 (5.4) 1 (0.6) 102 (61.1) 16 (9.6) 3 (1.8) 63 (37.7) 9 (5.4) 9 (5.4) 8 (4.8) 34 (20.4) 12 (7.2) 34 (20.4)
21 (16.3)a 108 (83.7)a 1 (0.8) 41 (31.8) 51 (39.5) 29 (22.5) 5 (3.9) 2 (1.6) 61 (47.3)c 12 (9.4) 5 (3.9) 51 (39.5) 8 (6.2) 7 (5.5) 3 (2.3) 45 (34.9)b 72 (57.6)a 46 (35.7)b
– – 1 (0.5) 69 (31.8) 81 (37.3) 53 (24.4) 10 (4.6) 3 (1.4) 120 (55.3) 15 (6.9) 4 (1.8) 83 (38.2) 16 (7.4) 6 (2.8) 9 (4.2) 79 (36.4) 71 (33.3) 80 (36.9)
– – 0 32 (29.4) 41 (37.6) 30 (27.5) 5 (4.6) 1 (0.9) 68 (62.4) 5 (4.6) 1 (0.9) 39 (35.8) 8 (7.3) 3 (2.8) 7 (6.5) 34 (31.2) 9 (8.3) 34 (31.2)
– – 1 (0.9) 37 (34.3) 40 (37.0) 23 (21.3) 5 (4.6) 2 (1.9) 52 (48.1)c 10 (9.3) 3 (2.8) 44 (40.7) 8 (7.4) 3 (2.8) 2 (1.9) 45 (41.7) 62 (59.6)a 46 (42.6)
– – 1 (1.3) 14 (17.7) 43 (54.4) 17 (21.5) 4 (5.1) 0 (0) 43 (54.4) 13 (16.5) 4 (5.1) 31 (39.2) 1 (1.3) 10 (12.8) 2 (2.5) 0 (0) 13 (16.5) 0 (0)
– – 1 (1.7) 10 (17.2) 32 (55.2) 11 (19.0) 4 (6.9) 0 (0) 34 (58.6) 11 (19.0) 2 (3.5) 24 (41.4) 1 (1.7) 6 (10.3) 1 (1.7) 0 (0) 3 (5.2) 0 (0)
– – 0 (0) 4 (19.0) 11 (52.4) 6 (28.6) 0 (0) 0 (0) 9 (42.9) 2 (9.5) 2 (9.5) 7 (33.3) 0 (0) 4 (20.0) 1 (4.8) 0 (0) 10 (47.6)a 0 (0)
–
–
–
210 (96.8)
102 (93.6)
108 (100.0)b
–
–
–
a
p < 0.001. b p < 0.01. c p < 0.05 in users compared to non-users with Chi Square test. Data presented as N (%). NIDDM: diabetes non-insulin dependent. HRT: hormone replacement therapy.
on AAC change in men or in women. This finding is in line with the literature [33,36,37], and is hypothesized to occur because ingestion of calcium and calcium supplementation have different biological effects on serum calcium. However, common sources of dietary calcium are often foods that promote cardiovascular health, such as leafy greens, legumes, seeds, and dairy products. It is therefore unclear whether the observed effects of dietary calcium are a result of a different biological handling mechanism or an overall healthier diet. The sex-specific differences in vascular calcification observed in our study warrant further investigation. Due to the low number of males in the Kingston CaMOS cohort, it is not possible to conclude that these results could be replicated in a larger, more sex-balanced study. A higher number of males would also be necessary for a multivariate analysis. As well, it is notable that while 97% of the women in this study were post-menopausal, the premenopausal women were not taking calcium supplements (n = 7). While it is difficult to draw any conclusions based on this low number of women, this may indicate that menopause could be a contributing factor to the progression of vascular calcification or alternatively it could indicate that menopausal women are simply more likely to be taking calcium supplements. Given that there are previously reported sex differences in the effects of calcium supplementation on vascular calcification [38] and cardiovascular events [39], it does appear that sex or menopause cannot be ruled out as a factor that influences the calcium supplementation-vascular calcification hypothesis. Both calcium supplement users and non-users lost BMD at all three sites, suggesting that calcium supplementation at this dose may not have a protective effect on BMD. This is consistent with a 2012 study that found a calcium supplement dose below 500 mg/day did not offer any BMD protection to femoral neck or total hip sites in older women [40]. It has been proposed that low-dose calcium supplements are most effective at preventing BMD loss in women with low dietary calcium intake (< 400 mg/day) [41]. As the women in our study had a much higher dietary intake than 400 mg/day and we saw no benefit of calcium supplements on BMD, our data could support this hypothesis. We saw a statistically significant decrease in BMD in male calcium supplement users at all three sites as compared to non-users. The
4. Discussion This longitudinal study investigated the associations between calcium supplement use, change in abdominal aortic calcification and change in bone mineral density over a 5-year period. Women who reported taking calcium supplements at entry had significantly greater AAC progression over a 5-year period than female non-users and males overall. Dietary calcium intake at entry was not associated with change in AAC in women or men. In addition, calcium supplement use at entry had no effect on BMD loss in women, and was associated with greater BMD loss in men. There was no association observed between AAC score change and BMD T-Score change over time in either men or women. The mechanism linking calcium supplementation to adverse cardiac outcomes is currently not well understood. One hypothesis is that excess calcium is deposited into the vasculature as a result of maladaptive mineral handling. In addition to the traditional cardiovascular risk factors such as age, smoking and hypertension, our results suggest calcium supplementation contributes to AAC, the latter of which has been found in a previous study to be correlated to serum calcium [33]. Taken together with the evidence suggesting serum calcium is linked to carotid artery plaque thickness [34] and that AAC predicts adverse cardiovascular outcomes [33,35], these findings may support vascular deposition of calcium as a potential mechanism of poor cardiovascular outcomes in association with calcium supplementation. Given that vascular calcification is a multi-factorial process, it is highly likely that there were other factors aside from calcium supplementation that contributed to the change in AAC in women, although we adjusted for known confounders in our multi-variable model. The women on calcium supplements in our study were on average 3 years older and a greater proportion of them had hypertension, both factors that contribute to increased vascular calcification independent of calcium supplementation. However, calcium supplement users also smoked less than non-users, and had lower AAC at baseline, which could suggest that the calcification seen was not solely due to these well-identified vascular risk factors. It is notable that dietary calcium does not appear to have an effect 4
5
(7.3) (4.9) (2.7) [11.0, 36.7]
(7.3) (4.5) (2.8) [11.8, 36.3]
−0.07 (0.04) −0.07 (0.03) −0.11 (0.03) 0 [0,0] 833.6 (460.5) 0 [0,0] 833.6 (460.5)
0 [0, 200] 1051.7 (577.6)
0 [0, 246] 834.0 (461.9)
1.73 (2.59) 3.24 (3.96) +1.51 (3.21)
65.2 28.2 14.0 19.5
−0.07 (0.57) −0.09 (0.38) −0.11 (0.36)
1.57 (2.32) 3.44 (3.87) +1.86 (3.23)
65.9 28.0 13.8 19.5
Calcium supplement non-users (n = 167) (7.1)c (5.3) (2.6) [9.2, 40.0] (7.0) (4.9) (2.7) [8.7, 35.7]
0 [0, 258] 1051.7 (577.6)
200 [0,400]a 1278.9a (626.2) 334.00 [196.43, 589.45]a 0 [0, 366] 834.7 (465.7) 831.0 (434.6)
−0.11 (0.59) −0.11 (0.40) −0.11 (0.36)
1.53 (2.24) 3.61 (3.97) 2.07 (3.35)
65.8 27.9 13.8 18.8
−0.08 (0.05) −0.17 (0.03) −0.11 (0.03)
1.37 (1.91) 3.69 (3.76) +2.32 (3.22)c
67.0 27.7 13.7 19.5
Calcium supplement users All (n = 217) (n = 129)
FEMALES
(7.0) (4.8) (2.7) [9.1, 36.7]
0 [0,0] 809.7 (420.4)
0 [0,0] 809.7 (420.4)
−0.16 (0.56) −0.12 (0.39) −0.15 (0.36)
1.81 (2.65) 3.35 (4.09) +1.54 (3.34)
64.8 28.0 14.2 19.1
Calcium supplement non-users (n = 109) (7.0)c (5.6) (2.7) [6.8, 34.6]
367 [200, 600] 853.6 (450.0)
200 [0,400]a 1308.0 (611.6)a
−0.6 (0.62) −0.10 (0.41) −0.08 (0.36)
1.26 (1.71) 3.87 (3.84) +2.61 (3.30)c
66.9 27.6 13.5 18.5
Calcium supplement users (n = 108)
0 [0, 43] 842.2 (532.3)
0 [0, 0] 944.2 (582.2)
0.02 (0.49) −0.05 (0.32) −0.10 (0.38)
1.68 (2.54) 2.96 (3.59) 1.28 (2.83)
66.3 (7.8) 28.58 (3.8) 13.8 (2.6) 25.5 [14.2, 38.8]
All (n = 79)
MALES
(7.9) (3.9) (2.8) [13.5 35.3]
0 [0,0] 878.8 (529.2)
0 [0,0] 878.8 (529.2)
+0.09 (0.47) +0.01 (0.31) −0.04 (0.40)
1.29 (2.50) 3.03 (3.74) +1.45 (3.00)
65.9 28.7 13.5 19.9
Calcium supplement non-users (n = 58)
(7.7) (3.6) (1.8) [25.5, 56.9]c
334 [136, 516.] 737.9 (540.9)
0. [0,400.]a 1130.6 (693.5)
−0.18 (0.51)c −0.19 (0.29)c −0.26 (0.24)c
1.95 (2.69) 2.76 (3.24) +0.81 (2.32)
67.4 28.2 14.6 43.8
Calcium supplement users (n = 21)
p < 0.001. b p < 0.01. c p < 0.05 in users compared to nonusers with t-test or Mann-Whitney U. All data presented as mean (SD), except vitamin D, calcium supplements and pack years of smoking presented as median [IQR]. *N = 153 for pack years; 94 for non users and 59 for users; 112 for women (62 for non users and 50 for users) and 41 for men (32 for non users and 9 for users).
a
Age BMI (kg/m2) Sedentary hours per day Pack years* (smokers only) AAC scores Baseline 5 year Absolute change BMD T-Score absolute change Lumbar Total hip Femoral neck Calcium and vitamin D Vitamin D (IU per day) Total calcium: supplements and diet (mg/day) Calcium supplements (mg/day) Dietary only calcium (mg/day)
All (n = 296)
ALL
Table 1b Baseline characteristics of study participants: continuous variables.
M. Hulbert, et al.
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Table 2 3-level AAC progression in women and men. FEMALES
Categorical variables Smoking history Heart attack CVA/TIA Hypertension NIDDM Kidney stones Kidney disease HRT Vitamin D supplement Anti-resorptive therapy Calcium supplement use Continuous variables Age BMI (kg/m2) Sedentary hours per day Pack yearsd (smokers only) AAC scores Baseline 5 year Absolute change Calcium and vitamin D Vitamin D (IU/day) Total calcium: supplements and diet (mg/day) Calcium supplements (mg/day) Dietary calcium (mg/day)
MALES
No progression (N = 100)
Moderate progression (N = 56)
Severe progression (N = 61)
No progression (N = 42)
Moderate progression (N = 21)
Severe progression (N = 16)
52 (52.0) 6 (6.0) 1 (1.0) 28 (28.0)a 5 (5.0) 1 (1.0) 4 (4.0) 38 (38.0) 31 (31.0) 38 (38.0) 39 (39.0)b
29 (51.8) 2 (3.6) 1 (1.8) 20 (35.7)a 4 (7.1) 1 (1.8) 2 (3.6) 19 (33.9) 21 (39.6) 19 (33.9) 35 (62.5)b
39 (63.9) 7 (11.7) 2 (3.3) 35 (57.4)a 7 (11.5) 4 (6.7) 3 (4.9) 22 (36.1) 19 (31.7) 23 (37.7) 34 (55.7)b
21 (100.0) 6 (14.3) 2 (4.9) 14 (33.3) 0 (0) 5 (11.9) 1 (2.4) 0 (0) 6 (14.3) 0 (0) 12 (28.6)
10 (47.6) 4 (19.0) 0 (0) 11 (52.4) 1 (4.8) 3 (15.0) 0 (0) 0 (0) 4 (19.0) 0 (0) 5 (23.8)
12 (75.0) 3 (18.8) 2 (12.5) 6 (37.5) 0 (0) 2 (12.5) 1 (6.3) 0 (0) 3 (18.8) 0 (0) 4 (25.0)
62.9 28.2 14.1 16.8
(6.3)a (5.3) (2.7) [7.0, 36.3]
66.7 28.1 13.8 17.9
(6.0)a (4.5) (2.7) [7.6, 31.6]
69.7 26.8 13.4 22.8
(7.1)a (5.6) (2.6) [9.4, 45.7]
65.8 28.4 13.4 25.5
(7.4)c (3.5) (2.6) [15.5, 42.8]
64.1 28.4 14.6 32.0
(8.0)c (3.7) (2.9) [17.9, 56.9]
70.4 29.3 13.6 15.0
(7.5)c (4.8) (2.4) [6.8, 35.0]
1.36 (2.26) 0.83 (1.80)a −0.53 (1.23)a
1.46 (2.19) 3.34 (2.34)a 1.87 (0.74)a
1.88 (2.24) 8.41 (3.15)a 6.52 (2.46)a
1.71 (2.49) 1.00 (1.81)c −0.71 (1.21)c
1.24 (2.45) 3.05 (2.48)c 1.81 (0.75)c
2.19 (2.83) 8.00 (3.48)c 5.81 (1.87)c
0 [0, 200] 949.3 (538.5)
0 [0, 400] 1159.8 (520.6)
0 [0, 349] 1112.2 (661.5)
0 [0, 0] 909.3 (462.8)
0 [0, 0] 1036.4 (738.2)
0 [0, 0] 918.2 (663.8)
0 [0, 200] 788.0 (412.8)c
162 [0, 321] 954.8 (482.8)c
160 [0, 539] 785.8 (405.9)c
0 [0, 86] 827.6 (448.5)
0 [0, 50] 929.7 (703.3)
0 [0, 24] 770.0 (506.4)
a
p < 0.001. b p < 0.01. c p < 0.05 any progression as compared to no progression. Chi-square test for categorical variables, T-test or Kruskal-Wallis for continuous variables. Categorical data presented at N (%). Continuous variables presented as mean (SD), except vitamin D, calcium supplements and pack years of smoking presented as median [IQR]. *N = 47, 27 and 36 (no, moderate, severe) respectively for women; 21, 12 and 11 for men.
explanation for this observation is not clear, but may be partially related to under-treatment particularly in male participants with low bone densities and osteoporosis as defined by the BMD. The multicenter CaMos cohort is an observational long-term study without clinical interventions by the investigators. However, there is a potential influence of the study design on the frequency of prescribing bone-active agents to study participants over time, since the DXA results were transmitted to the participants and/or their physician, as per ethics requirements for the study. Family physicians then could prescribe agents for low BMD. We found significant “care gaps’ in both women and men in the CaMos study. At baseline (year 1 of the study), 22% of the women who had experienced a fragility fracture were receiving a bisphosphonate and 26% were on hormone therapy (HT). We were not able to differentiate HT use for menopausal symptoms versus osteoporosis. Over a 10-year study period, 42–56% of women with yearly incident clinical fragility fractures were not treated with any osteoporosis medication [42]. Men had a larger care gap and at baseline and year five only 2.3% and 10.3% of men with a clinical fracture reported an osteoporosis
B
Participants (%)
100
Severe AAC Increase
80
Moderate AAC Increase
60
No AAC Progression
40 20 0
Non User
User
Calcium Supplement
5 Year Change in AAC (points)
A
4
Age
p<0.001
Calcium Supplements
p=0.002
Hypertension
p=0.002
BMI
Smoking
p=0.02
Diabetes
p=0.28
Overweight
p=0.36
Obese Class I
p=0.80
Obese Class II/III
p=0.08
HRT
p=0.17
Sedendary Hours
p=0.13
0
5
Odds Ratio ± 95% CI
Fig. 2. Multivariable model of aortic calcification progression in females. Logistic regression model with clinically relevant predictors of AAC progression over 5 years in women. Sedentary hours split at 14.
Calcium Supplement Non-User Calcium Supplement User
*
3 2 1 0
p=0.10
Vitamin D Supplements
Men
6
Women
Fig. 1. Progression of aortic calcification based on calcium supplement use overall and stratified by sex. (A) Participants separated by 5 year change in AAC by either no progression/decrease, moderate progression (1–3), or severe increase greater than 4 points. Calcium supplement users had more progression of AAC (Chi square, p = 0.036). (B) Change in AAC score over 5 years in female and male participants by calcium supplement use. Data presented as mean ± SEM. Two-Way ANOVA with post hoc Sidak-corrected T-tests comparing calcium supplement users to non-users. *p < 0.05.
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M. Hulbert, et al.
A
B
0.2
Calcium Supplement Non-User Calcium Supplement User
0.0
-0.2 -0.4 -0.8
Lumbar
Hip
Males 5 Year Change in BMD T-Score
5 Year Change in BMD T-Score
Female
0.2
0.0
-0.2
*
*
*
-0.4 Lumbar
Neck
BMD Measurement Location
Hip
Neck
BMD Measurement Location
Fig. 3. Bone mineral density changes by calcium supplement use stratified by sex. Change in BMD T-score over 5 years in (A) female and (B) male participants by calcium supplement use. Data presented as mean ± SEM. Users compared to nonusers with T-test. *p < 0.05.
longitudinal and fluctuating calcium supplement use and progression of vascular calcification. In conclusion, calcium supplementation, but not dietary calcium, appears to be related to vascular calcification in older women. As well, calcium supplementation did not provide any protection against BMD loss in older women and was associated with BMD loss in older men. Further studies on the role of calcium supplement-related vascular calcification in comparative groups of men and women are needed. These results suggest that vascular calcification may contribute to the increased cardiovascular events observed in calcium supplement users and support a negative risk-benefit ratio for calcium supplement use.
diagnosis, respectively. At year five, 90% of men with a clinical fragility fracture were still untreated [43]. The male calcium supplement users in this study had similar baseline BMD as non-users however whether these individuals were considered at higher risk for fractures for reasons such as a history of falls, and as such were placed on calcium supplements earlier than their peers is not known. Thus, this result could represent a failure of calcium supplementation for fracture prevention. The ineffectiveness of low dose calcium is supported by a study that found calcium doses under 600 mg/day did not provide any benefit to BMD change in older men [44]. However, due to the small sample size of men in our study, it cannot be concluded that calcium supplementation contributes to BMD loss in men based on this data alone. Notably, change in BMD at any site and change in AAC were not associated with each other in either sex, or overall. Supporting this finding, baseline BMD at any site and baseline AAC were also not significantly correlated with each other in men or in women (data not shown). This is consistent with some [38,45], but not all studies [26,46], indicating that further research is needed to understand the relationship between bone loss and extra-osseous calcification. There are several limitations to this study. Although the CaMOS cohort was randomly sampled, the sampling framework was developed to over-represent older women in this osteoporosis-focused study, resulting in a predominantly female, healthy, Caucasian population, thus restricting the generalizability to other groups. As well, it is important to remember that the presence of vascular calcification on its own is not a clinically significant outcome; further follow up studies on clinical risk are necessary to prove the significance of increases in AAC. As previously mentioned, there is a low number of male calcium supplement users (n = 21), making it difficult to draw conclusions on the sexspecific differences observed. Lastly, there were very few participants taking calcium supplements without Vitamin D. It is therefore not possible to separate the effects of either supplement from the other. A significant limitation of this study is the use of the study entry questionnaire data to establish calcium supplement user status and the absence of data on duration of use prior to the study start. Whilst this information is not available, a US national survey conducted at the same time as the entry questionnaire showed that supplement use was more likely in people who are healthy, older, Caucasian and female, and that this supplement use was likely to have occurred for at least 2 years [47]. This could support the notion that the calcium supplement users in our study were on these supplements for an extended period of time prior to the start, as well as offer a rationale behind the greater AAC increase observed in the female supplement users. Duration of calcium supplement use would be expected to play a significant role in the likelihood of developing vascular calcification. Long-term studies are necessary to resolve the temporal relationship between both
Author contributions The study was conceptualized and conducted by Maggie Hulbert, Tassos Anastassiades, Michael Adams and Rachel Holden. Mandy Turner and Wilma Hopman assisted with the statistical analysis. Declaration of competing interest Maggie Hulbert, Mandy Turner, Wilma Hopman, Tassos Anastassiades, Michael Adams and Rachel Holden declare that they have no conflict of interest. Acknowledgements The Authors acknowledge the Canadian Institutes of Health Research (CIHR) for supporting the collection of all of the data used in this study, through the Canadian Multicenter Osteoporosis Study (CaMos), including the Kingston site. Funding was over a period of approximately 20 years. Appendix A. Supplementary data Supplementary data to this article can be found online at https:// doi.org/10.1016/j.atherosclerosis.2019.12.003. References [1] K.M. Mangano, et al., Calcium intake in the United States from dietary and supplemental sources across adult age groups: new estimates from the National Health and Nutrition Examination Survey 2003-2006, J. Am. Diet. Assoc. 111 (5) (2011) 687–695. [2] H.B. Del Valle, A.L. Yaktine, C.L. Taylor, A.C. Ross, Dietary reference intakes for calcium and vitamin D, in: A.C. Ross, et al. (Ed.), Dietary Reference Intakes for Calcium and Vitamin D, 2011 Washington (DC). [3] I.R. Reid, et al., Long-term effects of calcium supplementation on bone loss and fractures in postmenopausal women: a randomized controlled trial, Am. J. Med. 98
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predictor of cardiovascular events: a meta-analysis, Heart 98 (13) (2012) 988–994. [26] D.P. Kiel, et al., Bone loss and the progression of abdominal aortic calcification over a 25 year period: the Framingham Heart Study, Calcif. Tissue Int. 68 (5) (2001) 271–276. [27] W. Zhou, et al., Longitudinal changes in calcium and vitamin D intakes and relationship to bone mineral density in a prospective population-based study: the Canadian Multicentre Osteoporosis Study (CaMos), J. Musculoskelet. Neuronal Interact. 13 (4) (2013) 470–479. [28] G. Ioannidis, et al., Glucocorticoids predict 10-year fragility fracture risk in a population-based ambulatory cohort of men and women: Canadian Multicentre Osteoporosis Study (CaMos), Arch. Osteoporos. 9 (2014) 169. [29] J.M. Muir, et al., The effect of regular physical activity on bone mineral density in post-menopausal women aged 75 and over: a retrospective analysis from the Canadian multicentre osteoporosis study, BMC Muscoskelet. Disord. 14 (2013) 253. [30] M. Grant, et al., A novel quantitative approach to the measurement of abdominal aortic calcification as applied to the Canadian Multicenter Osteoporosis Study (CaMOS), Bone 97 (2017) 201–208. [31] C. Berger, et al., Peak bone mass from longitudinal data: implications for the prevalence, pathophysiology, and diagnosis of osteoporosis, J. Bone Miner. Res. 25 (9) (2010) 1948–1957. [32] N. Kreiger, et al., Research notes: the Canadian multicentre osteoporosis study (CaMos): background, rationale, methods, Can. J. Aging 18 (3) (1999) 376–387. [33] M.J. Bolland, et al., Abdominal aortic calcification on vertebral morphometry images predicts incident myocardial infarction, J. Bone Miner. Res. 25 (3) (2010) 505–512. [34] M.R. Rubin, et al., Carotid artery plaque thickness is associated with increased serum calcium levels: the Northern Manhattan study, Atherosclerosis 194 (2) (2007) 426–432. [35] J.T. Schousboe, et al., Abdominal aortic calcification detected on lateral spine images from a bone densitometer predicts incident myocardial infarction or stroke in older women, J. Bone Miner. Res. 23 (3) (2008) 409–416. [36] M. Umesawa, et al., Dietary intake of calcium in relation to mortality from cardiovascular disease: the JACC Study, Stroke 37 (1) (2006) 20–26. [37] E.G. Knox, Ischaemic-heart-disease mortality and dietary intake of calcium, Lancet 1 (7818) (1973) 1465–1467. [38] T.K. Wang, et al., Relationships between vascular calcification, calcium metabolism, bone density, and fractures, J. Bone Miner. Res. 25 (12) (2010) 2777–2785. [39] Q. Xiao, et al., Dietary and supplemental calcium intake and cardiovascular disease mortality: the National Institutes of Health-AARP diet and health study, JAMA Intern. Med. 173 (8) (2013) 639–646. [40] K. Nakamura, et al., Effect of low-dose calcium supplements on bone loss in perimenopausal and postmenopausal Asian women: a randomized controlled trial, J. Bone Miner. Res. 27 (11) (2012) 2264–2270. [41] B. Dawson-Hughes, et al., A controlled trial of the effect of calcium supplementation on bone density in postmenopausal women, N. Engl. J. Med. 323 (13) (1990) 878–883. [42] L.A. Fraser, et al., Fragility fractures and the osteoporosis care gap in women: the Canadian Multicentre Osteoporosis Study, Osteoporos. Int. 22 (3) (2011) 789–796. [43] A. Papaioannou, et al., The osteoporosis care gap in men with fragility fractures: the Canadian Multicentre Osteoporosis Study, Osteoporos. Int. 19 (4) (2008) 581–587. [44] I.R. Reid, et al., Randomized controlled trial of calcium supplementation in healthy, nonosteoporotic, older men, Arch. Intern. Med. 168 (20) (2008) 2276–2282. [45] K. Aoyagi, et al., Low bone density is not associated with aortic calcification, Calcif. Tissue Int. 69 (1) (2001) 20–24. [46] M. Naves, et al., Progression of vascular calcifications is associated with greater bone loss and increased bone fractures, Osteoporos. Int. 19 (8) (2008) 1161–1166. [47] K. Radimer, et al., Dietary supplement use by US adults: data from the national health and nutrition examination survey, 1999-2000, Am. J. Epidemiol. 160 (4) (2004) 339–349.
(4) (1995) 331–335. [4] I.R. Reid, et al., Randomized controlled trial of calcium in healthy older women, Am. J. Med. 119 (9) (2006) 777–785. [5] D.J Hosking, et al., Evidence that increased calcium intake does not prevent early postmenopausal bone loss, Clin. Ther. 5 (1998) 933–944 Sep-Oct. [6] I.R. Reid, et al., Determinants of the rate of bone loss in normal postmenopausal women, J. Clin. Endocrinol. Metab. 79 (4) (1994) 950–954. [7] K. Uusi-Rasi, et al., Influence of calcium intake and physical activity on proximal femur bone mass and structure among pre- and postmenopausal women. A 10-year prospective study, Calcif. Tissue Int. 82 (3) (2008) 171–181. [8] K. Nakamura, et al., Nutritional and biochemical parameters associated with 6-year change in bone mineral density in community-dwelling Japanese women aged 69 years and older: the Muramatsu Study, Nutrition 28 (4) (2012) 357–361. [9] H.A. Bischoff-Ferrari, et al., Calcium intake and hip fracture risk in men and women: a meta-analysis of prospective cohort studies and randomized controlled trials, Am. J. Clin. Nutr. 86 (6) (2007) 1780–1790. [10] I.R. Reid, S.M. Bristow, M.J. Bolland, Calcium supplements: benefits and risks, J. Intern. Med. 278 (4) (2015) 354–368. [11] J. Hsia, et al., Calcium/vitamin D supplementation and cardiovascular events, Circulation 115 (7) (2007) 846–854. [12] M.J. Bolland, et al., Calcium supplements with or without vitamin D and risk of cardiovascular events: reanalysis of the Women's Health Initiative limited access dataset and meta-analysis, BMJ 342 (2011) d2040. [13] J.M. Paik, et al., Calcium supplement intake and risk of cardiovascular disease in women, Osteoporos. Int. 25 (8) (2014) 2047–2056. [14] K. Li, et al., Associations of dietary calcium intake and calcium supplementation with myocardial infarction and stroke risk and overall cardiovascular mortality in the Heidelberg cohort of the European Prospective Investigation into Cancer and Nutrition study (EPIC-Heidelberg), Heart 98 (12) (2012) 920–925. [15] K. Michaelsson, et al., Long term calcium intake and rates of all cause and cardiovascular mortality: community based prospective longitudinal cohort study, BMJ 346 (2013) f228. [16] V.A. MoyerU.S.P.S.T, Force*, Vitamin D and calcium supplementation to prevent fractures in adults: U.S. Preventive Services Task Force recommendation statement, Ann. Intern. Med. 158 (9) (2013) 691–696. [17] J.R. Lewis, et al., The effects of calcium supplementation on verified coronary heart disease hospitalization and death in postmenopausal women: a collaborative metaanalysis of randomized controlled trials, J. Bone Miner. Res. 30 (1) (2015) 165–175. [18] R.L. Prentice, et al., Health risks and benefits from calcium and vitamin D supplementation: women's Health Initiative clinical trial and cohort study, Osteoporos. Int. 24 (2) (2013) 567–580. [19] D. Challoumas, C. Cobbold, G. Dimitrakakis, Effects of calcium intake on the cardiovascular system in postmenopausal women, Atherosclerosis 231 (1) (2013) 1–7. [20] M. Chung, et al., Calcium intake and cardiovascular disease risk: an updated systematic review and meta-analysis, Ann. Intern. Med. 165 (12) (2016) 856–866. [21] S.L. Kopecky, et al., Lack of evidence linking calcium with or without vitamin D supplementation to cardiovascular disease in generally healthy adults: a clinical guideline from the national osteoporosis foundation and the American society for preventive Cardiology, Ann. Intern. Med. 165 (12) (2016) 867–868. [22] P.L. Lutsey, E.D. Michos, Vitamin D, calcium, and atherosclerotic risk: evidence from serum levels and supplementation studies, Curr. Atheroscler. Rep. 15 (1) (2013) 293. [23] J.J. Anderson, et al., Calcium intake from diet and supplements and the risk of coronary artery calcification and its progression among older adults: 10-year follow-up of the multi-ethnic study of atherosclerosis (MESA), J Am Heart Assoc 5 (10) (2016). [24] M.J. Blaha, et al., Understanding the utility of zero coronary calcium as a prognostic test: a Bayesian approach, Circ. Cardiovasc. Qual. Outcomes 4 (2) (2011) 253–256. [25] F. Bastos Goncalves, et al., Calcification of the abdominal aorta as an independent
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