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Hypertension and its associated risks among Singapore elderly residential population
Journal of Clinical Gerontology & Geriatrics 6 (2015) 125e132
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Original article
Hypertension and its associated risks among Singapore elderly residential population Lee Seng Esmond Seow, BA *, Mythily Subramaniam, MBBS, MHSM, Edimansyah Abdin, PhD, Janhavi Ajit Vaingankar, MSc, Siow Ann Chong, MBBS, MMed, MD Research Division, Institute of Mental Health, Singapore
a r t i c l e i n f o
a b s t r a c t
Article history: Received 12 February 2015 Received in revised form 29 April 2015 Accepted 5 May 2015 Available online 15 June 2015
Background: Studies have shown hypertension to be a common health problem among the elderly. The prevalence, awareness, treatment, and control of hypertension, along with their sociodemographic and health-related correlates were established in a national cross-sectional epidemiological study of the elderly in Singapore. The associations between hypertension and select medical risks were also investigated. Methods: Data was collected from 2488 randomly selected elderly ( 60 years) as part of the Well-being of the Singapore Elderly (WiSE) study that involved face-to-face surveys and physical examination. Sitting blood pressure (BP) was measured twice with a 1 minute interval and averaged. Hypertension was defined by a systolic blood pressure (SBP) 140 mmHg, and/or a diastolic blood pressure (DBP) 90 mmHg, and/or current treatment with anti-hypertensive medication. Results: The prevalence of hypertension in this population was 74.1%. The rate of hypertension was associated with older age, lower education, and higher body mass index (BMI). Those who were Malay, retired and very physically active were more likely to be unaware of being hypertensive. An age of 85 years, being unemployed, widowed or divorced/separated, and being a non-smoker were associated with uncontrolled hypertension. Those with hypertension were also more likely to report a diagnosis of diabetes. Conclusion: The proportion of elderly with hypertension is high in this Asian population. What is of concern is the substantial proportion of undetected cases. This highlights the need for effective health screening among the elderly. Optimal control of BP in those diagnosed with hypertension is also a cause for concern, as identified in our study. Copyright © 2015, Asia Pacific League of Clinical Gerontology & Geriatrics. Published by Elsevier Taiwan LLC. Open access under CC BY-NC-ND license.
Keywords: awareness control epidemiology hypertension prevalence treatment
1. Introduction Hypertension is a chronic health problem that involves the primary elevation of systemic blood pressure (BP), otherwise known as high BP. It is a global public health issue that affects approximately 1 billion people worldwide in both developed and developing countries.1 Prevalence of hypertension increases with age and hence the elderly tend to have the highest prevalence within a particular population,2,3 reaching as high as 60e80% in developed nations.2,4
* Corresponding author. Research Division, Institute of Mental Health, Buangkok Green Medical Park, 10 Buangkok View, Singapore 539747, Singapore. E-mail address: [email protected] (L.S.E. Seow).
The Framingham Heart Study found that the residual lifetime risks of developing hypertension through to the age of 80 years for men and women who were normotensive at age 55 years are 93% and 91% respectively. This means that more than 90% of individuals who are free from hypertension at 55 years of age will eventually develop it during their remaining life span.5 As the world population ages progressively along with a concomitant increase in life expectancy, the issue of hypertension among the elderly has become a further cause for concern. Hypertension is a widely recognised major risk factor for cardiovascular disease such as stroke and myocardial infarction, as well as for chronic kidney diseases and congestive heart failure among men and women,6,7 making it the leading cause of morbidity and mortality among the elderly. In addition, it has been suggested that hypertension increases the risk of dementia
http://dx.doi.org/10.1016/j.jcgg.2015.05.002 2210-8335/Copyright © 2015, Asia Pacific League of Clinical Gerontology & Geriatrics. Published by Elsevier Taiwan LLC. Open access under CC BY-NC-ND license.
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and cognitive decline among the elderly.8,9 The evidence supporting the relationship between hypertension and depression, however, remains controversial.10,11 Generally, it was reported that the elderly have higher expenditures per capita for hypertension and related diseases.12 The annual cardiovascular costs (including health care services, medication, and missed days of work) associated with hypertension in the United States for people aged 65e79 years are projected to increase by 238%, from $135 billion to $457 billion per year, from 2010 to 2030.13 Better control of hypertension among the elderly requires an increase in awareness among the population and improved effectiveness of pharmacological and non-pharmacological interventions.14 Early detection and treatment aids in minimizing the medical care costs associated with hypertension and the other diseases for which people with hypertension are at increased risk. Randomized, controlled clinical trials have demonstrated significant clinical benefits in treating hypertension among the elderly.15e17 In a metaanalysis involving 15,693 elderly participants with isolated systolic hypertension in eight clinical trials against placebo, the risk of stroke was reduced by 30%, coronary heart disease events by 23%, all cardiovascular complications by 26%, and cardiovascular mortality by 18% upon active drug therapy.18 Singapore has an aging population with those aged 65 years making up 11% of the residential population in 2014.19 Many studies have identified the effects of demographic and lifestyle factors such as gender, age, socioeconomic status,20,21 smoking,21,22 body mass index (BMI),23 exercise22,24 and alcohol consumption25 on BP among the elderly. However, such characteristics are not uniform across countries due to key differences in demographics indicators (e.g., ethnicity) and level of socioeconomic deprivation. Hence, epidemiological analysis needs to be conducted in the local context for better planning and management of hypertension in any population. In this study, our aims were to: (1) investigate the prevalence, awareness, treatment, and adequacy of control of hypertension; (2) examine their respective sociodemographic and health-related correlates; and (3) investigate the association between hypertension and select lifetime medical conditions (self-reported) among the elderly population in Singapore. 2. Methods 2.1. Study overview Data was collected as part of the Well-Being of the Singapore Elderly (WiSE) study, a cross-sectional household survey involving face-to-face interview and physical examination conducted from October 2012 to December 2013. The door-to-door visits were preceded by an extensive training program for the field interviewers who were individually assessed for their proficiency and skill in performing the necessary procedures. Participants were given an inconvenience fee upon completion of the survey. The study was approved by the relevant ethics committees in Singapore i.e. the National Healthcare Group, Domain Specific Review Board, and the SingHealth Centralised Institutional Review Board. The study methodology has been described in detail in a prior article.26 2.2. Study participants The respondents in the study were Singapore residents (including Singapore citizens and permanent residents) aged 60 years who were living in Singapore. They were randomly selected from a national database that maintains the names, sociodemographic information such as age, gender, ethnicities, and household addresses of all residents. Efforts were made to follow up on residents who were admitted to, or residing in a hospital or nursing home during the course of the study. Residents who were living
outside the country and those not contactable due to incomplete or incorrect addresses were excluded from the study. Prior to participation, written informed consent was obtained from all respondents and in the case of participants who were unable to provide informed consent, a written informed consent was taken from their legally acceptable representative or next of kin. To increase the precision of subgroup estimation, a disproportionate stratified sampling (by age group and ethnicity) was planned, where the three main ethnic groupsdChinese, Malay, and Indiandwere sampled in proportions of approximately 40%, 30%, and 30% respectively. Individuals aged 75 years were also over-sampled. Sociodemographic information including age, gender, ethnicity, marital status, education, employment status, as well as level of physical activity and smoking status were collected using a structured questionnaire. The interviewers also measured the height and weight of each respondent to obtain their BMI for risk assessment of cardiovascular disease. The suggested categories based on Asian populations27 are as follows: (1) underweight (< 18.5 kg/m3); (2) increasing, but acceptable risk of cardiovascular disease (18.5e23.0 kg/m3); (3) increased risk (23.0e27.5 kg/m3); and (4) high risk (> 27.5 kg/m3). 2.3. Measurement of BP During the course of the visit, resting BP was measured twice, with a 1 minute interval, by the trained interviewers using an electronic sphygmomanometer (Omron HEM-7211; Omron Healthcare). Participants were advised to relax in a sitting position, with their left elbow raised to the heart level and were asked to abstain from eating, drinking alcohol or caffeinated beverages, exercising or smoking for at least 30 minutes prior to their BP measurement. The mean of the two readings was used to define the systolic (SBP) and diastolic (DBP) blood pressure. 2.4. Definitions Hypertension was defined as having a SBP 140 mmHg, a DBP 90 mmHg, and/or undergoing current treatment with antihypertensive medication. This definition excludes hypertensive individuals who have attained a BP level in the normotensive range by non-pharmacological means.28 Awareness of hypertension was defined as a prior diagnosis by a doctor. Treatment of hypertension was defined as the current pharmacological treatment initiated by the doctors for lowering elevated BP. Control of hypertension was defined as having a current SBP < 140 mmHg and DBP < 90 mmHg associated with the pharmacological treatment. 2.5. Statistical analyses All estimates were weighted to adjust for over-sampling and post-stratified for age and ethnicity distributions between the survey sample and the Singapore resident population in 2011. Mean and standard error were calculated for BP values, and frequencies and percentages for all other categorical variables. We also examined the mean and distribution of BP classes, as defined by the Joint National Committee on Prevention, Detection, Evaluation and Treatment of High Blood Pressure (JNC-7)28, in the study sample across age, gender, and ethnicity. For the purpose of the study, a series of multiple logistic regression analyses were performed to study the impact of select sociodemographic and health-related factors on the prevalence of hypertension. We used hypertension status as the main outcome variable, with age, gender, ethnicity, marital status, education, employment status, BMI, exercise, and smoking as predictor variables. Respondents' awareness, treatment and control of hypertension were also investigated. The association between
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hypertension and the self-reporting of lifetime heart problems (heart attack, angina, heart failure, and valve disease), diabetes, transient ischemic attacks (TIAs), and stroke were also established after controlling for confounding variables. Standard errors (SE) and significance tests were determined using the Taylor series linearization method. Multivariate significance was evaluated using Wald Chi-square test based on designcorrected coefficient varianceecovariance matrices. Statistical significance was set at p < 0.05 using two-sided tests. All statistical analyses were carried out using the SAS version 9.2 (SAS Institute Inc., Cary, NC, USA). 3. Results 3.1. Study sample characteristics Of the 2565 respondents interviewed for the WiSE study, 2488 individuals agreed to BP measurements. Table 1 presents the sociodemographic and health-related characteristics of the elderly participants. 3.2. Mean BP levels and JNC-7 BP classification (across age, gender, and ethnicity) Table 2 presents the distribution of BP among the respondents according to the recommendation by JNC-7. Mean BP (± SE) was Table 1 Characteristics of the study participants (n ¼ 2488). Variable Age group (y) 60e74 75e84 85þ Gender Men Women Ethnicity Chinese Malay Indian Others Marital status Never married Married/cohabiting Widowed Divorced/separated Education None Some, but did not complete primary Completed primary Completed secondary Completed tertiary Employment Paid work (part-time & full-time) Unemployed Homemaker Retired BMI Underweight (< 18.5) Low risk (Healthy range; 18.5e22.9) Moderate risk (23.0e27.4) High risk ( 27.5) Exercise Very physically active Fairly physically active Not very physically active Not at all physically active Smoking No Yes BMI ¼ body mass index.
n
Unweighted %
Weighted %
1461 652 375
58.7 26.2 15.1
75.4 19.4 5.2
1098 1390
44.1 55.9
44.3 55.7
994 714 745 35
40.0 28.7 29.9 1.4
83.7 9.0 5.9 1.4
134 1452 795 105
5.4 58.4 32.0 4.2
8.1 64.2 22.2 5.6
493 588 627 511 257
19.9 23.7 25.3 20.6 10.4
16.4 23.5 25.0 22.6 12.5
682 32 775 971
27.7 1.3 31.5 39.5
34.2 1.6 26.1 38.1
142 629 887 582
6.3 28.1 39.6 26.0
5.5 32.2 42.0 20.4
344 1329 453 349
13.9 53.7 18.3 14.1
16.8 59.6 17.1 6.4
2251 233
90.6 9.4
90.3 9.7
127
141.4 ± 0.6/75.2 ± 0.3 mmHg. DBP was found to decline with age and was lower among women. Malays had the highest SBP and DBP levels. Around 31.7% of the elderly had current stage 1 or 2 hypertension; the proportion increased with age, did not vary with gender, and was highest among those of Malay ethnicity in Singapore. 3.3. Prevalence of hypertension and of awareness, treatment, and control of hypertension Of the 2488 respondents, nearly three-quarters (74.1%) of the elderly population had hypertension. Among those who had hypertension, slightly more than three-quarters (76.0%) were aware of their condition. A majority of those who were aware of their elevated BP were also on treatment. Nearly half of the treated hypertensive subjects satisfied JNC-7 recommendations for adequate BP control. Thirty-eight respondents did not currently have hypertension despite not receiving pharmacological treatment following prior diagnosis by a doctor. Data on the awareness, treatment, and control of hypertensive participants in our study sample are displayed in Figure 1 and Table 3. 3.4. Correlates of hypertension and of awareness and control of hypertension Based on data presented in Figure 1, two at-risk groups with elevated BP were identifieddthose who were unaware that they had hypertension and those who had suboptimal BP control despite treatment. Those who were untreated upon diagnosis (n ¼ 56) were excluded as their number was too small for any conclusive statistical analyses or meaningful comparison. The odds of hypertension were significantly higher among elderly participants aged 75e84 years compared to those aged 60e74 years (Table 4). Those who did not have any education or did not complete primary education and those with moderate or high risk BMI were more likely to have hypertension. The hypertensive elderly who were unaware of their condition were more likely to be Malays (compared to Chinese) and to be very physically active. Those who were retired were less likely to be unaware that they have hypertension than those doing paid work (part-time or fulltime). Elderly with suboptimal BP control despite treatment were more likely to be in the oldest age group (85þ years) and unemployed. In addition, they were more likely to be widowed or divorced/separated than married or cohabiting. Those who smoked were more likely to have their BP controlled with treatment. 3.5. Association of hypertension with reporting of lifetime medical conditions After controlling for age, education and BMI (factors associated with prevalence of hypertension), elderly with hypertension were found to have higher odds of reporting lifetime diabetes [odds ratio (OR) of 1.70, 95% confidence interval (CI) of 1.19e2.43], compared to those without hypertension. No significant relationship was found between hypertension and other lifetime conditions such as heart problems, TIAs, and stroke. 4. Discussion The WiSE study is the second to provide information on the prevalence, awareness, treatment, and control of hypertension along with their relevant correlates among the local elderly. The Singapore Social Isolation, Health, and Lifestyle Survey (SIHLS) conducted in 200929 was the first to present a comprehensive picture of hypertension management among the Singapore elderly.
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Table 2 Mean systolic and diastolic blood pressure, and distribution of blood pressure classes by the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure; overall and by age, gender, and ethnicity. BP levels (mmHg), mean (SE)
All Age group (y) 60e74 75e84 85þ Gender Men Women Ethnicity Chinese Malay Indian Others
BP categories based on JNC-7. Weighted row, n (%)
SBP
DBP
Normal
HigheNormal
Stage 1
Stage 2
141.4 (0.6)
75.2 (0.3)
316 (13.4)
1322 (54.9)
619 (23.6)
231 (8.1)
140.8 (0.7) 143.8 (1.1) 142.6 (1.6)
76.5 (0.4) 72.2 (0.6) 68.7 (0.8)
187 (13.9) 66 (10.9) 63 (16.3)
840 (56.8) 330 (51.5) 152 (40.6)
337 (22.7) 178 (25.6) 104 (28.3)
141.0 (0.8) 141.8 (0.8)
76.8 (0.5) 74.0 (0.4)
152 (12.6) 164 (14.1)
588 (55.8) 734 (54.2)
276 (24.5) 343 (22.9)
140.9 148.1 139.9 138.6
74.9 78.4 75.5 73.2
138 61 112 5
525 384 397 16
238 185 183 13
(0.7) (0.9) (0.8) (2.7)
(0.4) (0.5) (0.4) (2.4)
(13.9) (7.5) (15.3) (14.9)
(54.9) (56.4) (55.1) (47.1)
(23.1) (26.3) (23.1) (36.5)
97 (6.7) 78 (12.0) 56 (14.8) 82 (7.2) 149 (8.8) 93 84 53 1
(8.2) (9.8) (6.6) (1.6)
BP ¼ blood pressure; DBP ¼ diastolic blood pressure; JNC-7 ¼ Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure; SBP ¼ systolic blood pressure.
The two studies (WiSE and SIHILS) reported prevalence rates of 74.1% and 73.9%, awareness rates of 76.0% and 69.2%, treatment rates of 95.8% and 98.1% and, control rates of 48.9% and 35.4% respectively. In terms of prevalence and treatment rates, the findings were almost comparable. The awareness and control rates were higher in this study by 6.8% and 13.5% respectively. As reported by Malhotra et al29, Singapore has reported a higher prevalence of hypertension among the elderly population compared to most studies conducted in other countries but the awareness and treatment rates were also higher. In line with these findings, the World Health Organization's Study on Global Aging and Adult Health (SAGE)30 reported mean prevalence, awareness, control and treatment efficacy rates of 52.9%, 48.3%, 10.2%, and 26.3% respectively, across six countries, namely China, Ghana, India, Mexico, the Russian Federation, and South Africa. With the average life span extending worldwide, people are increasingly developing diseases of old age including hypertension.31 With Singapore being one of the fastest aging populations and its life expectancy rate at a high of 82.3 years in 2013,32 the high prevalence of hypertension among the elderly is not surprising. The prevalence or risk of hypertension also tends to be higher in more developed countries,33 as well as among the Asian compared to the Western populations at any given level of BMI, waist circumference, and waist-to-hip ratio.34 Lastly, other possible reasons for the variation in prevalence rate among countries could be due to difference in demographics such as ethnic makeup as well as different lifestyles factors (e.g., diet and physical activity). High salt intake may have contributed to the high prevalence observed in the study. The National Nutrition Survey in 2010
revealed that eight out of ten Singaporeans exceed their recommended daily salt intake, with the average person consuming 8.3 g daily which is 60% above recommended level of 5 g per day for adults. The rates of awareness, treatment, and control tend to be higher in developed countries including Singapore, possibly due to better management of hypertension cases compared to developing countries which have high illiteracy rates, poor access to health facilities, poverty, and high costs of drugs.33,35 In addition, continuous nationwide efforts by health care organizations such as the Health Promotion Board in promoting awareness of chronic diseases and healthy lifestyles have played an essential role in the higher awareness and control of hypertension among Singaporeans. The Health Promotion Board was established in 2001 by the Ministry of Health of Singapore to act as the main driver for national health promotion and disease prevention programs, with its vision being to build a nation of “healthy people”. In our current study, all non-modifiable sociodemographic and modifiable health-related factors including age, ethnicity, marital status, education, employment status, BMI, exercise, and smoking, but excluding gender, were associated with hypertension prevalence, awareness, and control. The pattern of association between hypertension prevalence and gender varied across countries but overall worldwide data revealed no significant gender difference.36 Most of our findings were similar to previous studies. We found hypertension to be associated with older age and higher BMI, consistent with a number of other studies.4,21,22,29,37 SBP tends to show continuous increase until the 8th decade of life.38 This is expected as advancing age is associated with a degenerative process
Figure 1. Hypertension and its awareness, treatment and control among Singapore elderly. Data are presented as n (weighted %).
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Table 3 Weighted prevalence of hypertension and of elderly with hypertension who were unaware, treated or uncontrolled. With hypertensiona Age group (y) 60e74 75e84 85þ Gender Men Women Ethnicity Chinese Malay Indian Others Marital status Never married Married/cohabiting Widowed Divorced/separated Education None Some, but did not complete primary Completed primary Completed secondary Completed tertiary Employment Paid work (part- & full-time) Unemployed Homemaker Retired BMI Underweight (< 18.5) Low risk (Healthy; 18.5e22.9) Moderate risk (23.0e27.4) High risk ( 27.5) Exercise Very physically active Fairly physically active Not very physically active Not at all physically active Smoking No Yes
Unaware hypertensivesa
Treated hypertensivesa
Uncontrolled hypertensivesa
1089 (71.3) 553 (85.0) 277 (74.2)
788 (73.6) 436 (82.9) 216 (80.8)
730 (95.2) 411 (97.4) 206 (96.0)
364 (50.0) 218 (51.5) 124 (61.7)
824 (74.6) 1095 (73.7)
595 (74.7) 845 (77.1)
557 (96.8) 790 (95.0)
279 (49.4) 427 (52.3)
741 575 578 25
(73.3) (81.2) (76.8) (69.6)
580 400 441 19
(77.0) (69.1) (75.0) (73.9)
537 371 420 537
(95.8) (94.1) (97.7) (95.8)
280 215 200 11
(50.6) (57.9) (45.6) (56.2)
91 1107 648 72
(60.9) (74.5) (81.0) (62.7)
64 815 511 49
(66.9) (75.4) (81.1) (71.3)
58 762 483 44
(92.5) (95.8) (98.0) (89.7)
31 359 285 31
(54.3) (46.0) (58.4) (76.4)
408 467 482 385 171
(85.3) (78.5) (70.0) (71.6) (64.0)
302 359 360 276 138
(77.7) (76.9) (75.1) (71.3) (82.6)
285 330 343 256 128
(96.8) (93.5) (98.4) (94.2) (96.5)
148 190 179 130 57
(50.4) (55.8) (50.8) (47.7) (49.2)
488 21 643 750
(68.4) (75.0) (77.4) (77.6)
312 15 504 597
(67.7) (76.6) (78.5) (80.9)
284 13 475 564
(94.7) (97.8) (97.5) (95.4)
135 10 264 289
(43.5) (89.5) (53.6) (52.1)
93 449 714 486
(64.8) (66.3) (78.1) (81.2)
59 310 548 380
(67.7) (71.6) (78.8) (75.3)
51 291 508 366
(93.5) (95.3) (96.0) (97.6)
25 154 269 195
(45.8) (48.6) (53.7) (51.8)
247 1031 363 271
(69.3) (73.9) (77.7) (81.5)
169 761 286 221
(69.5) (74.8) (82.1) (87.3)
150 717 272 205
(89.6) (97.5) (95.3) (95.5)
75 381 141 107
(48.8) (52.2) (48.3) (52.8)
1753 (74.7) 164 (69.5)
1348 (77.0) 90 (66.2)
1263 (95.6) 82 (97.8)
671 (52.1) 33 (39.9)
BMI ¼ bodyemass index. a Data are presented as n (weighted %).
that involves the thickening and loss of elasticity of arteries, hence contributing to high BP.39 Being overweight and obese is known to stimulate sympathetic nervous system activity, fasting plasma insulin, and leptin which can lead to elevated BP levels.40 Our study also found hypertension to be inversely associated with education where individuals who did not have any formal education or had not completed primary education were more likely to have hypertension, compared to those who had tertiary education. Low education has been associated with elevated levels of BP and related cardiovascular diseases, possibly due to the lack of awareness of hypertension prevention and control, and of adherence to medical treatment.41 The inverse relationship between educational attainment and incidence of hypertension was also observed in other hypertension studies in Brazil,42 Vietnam43, and Saudi Arabia.44 In terms of awareness of hypertension, the Malays had significantly lower rate of awareness compared to the Chinese and this finding is consistent with other studies.29,45 Those who were retired were less likely to be unaware of their condition,46,47 since they tend to have more time to focus on their health and seek early management of adverse health conditions. Unemployment was associated with a higher risk of uncontrolled hypertension. Being unemployed or having a low income could possibly have a negative impact on the ability of individuals to purchase prescribed
antihypertensive drugs and thus, lead to low medication compliance.48 Those who were widowed or divorced/separated (no longer partnered) were more likely to have uncontrolled hypertension.20,49,50 Individuals who had close daily contact with a spouse or partner tend to find themselves adopting health promoting behavior through social direct control such as encouraging, monitoring, reminding, and even threatening.51,52 Older individuals in our study also had higher rate of uncontrolled hypertension since BP usually gets more difficult to control with increasing age.53 Finally, our study revealed that elderly with hypertension were at higher risk of diabetes which is supported by a vast amount of research.54e56 A number of interesting findings were noted. Firstly, our results showed that elderly who were very physically active were more likely to be unaware of their hypertensive condition. This finding is contrary to what was found in another study.44 Possible explanations would be that our elderly respondents might have overestimated their level of physical activity (e.g., regarding regular low-intensity tai chi or walking as high physical activities) or that those with high physical activity levels might have been overconfident about their health status, and thus forgone the essential visits to the doctors for medical screenings. Nonetheless, the association of high physical activity leading to awareness of chronic
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Table 4 Sociodemographic and health-related correlates of hypertension, unawareness, and lack of blood pressure control among treated hypertensives. With hypertension OR Age group (y) 60e74 75e84 85þ Gender Men Women Ethnicity Chinese Malay Indian Others Marital status Never married Married/cohabiting Widowed Divorced/separated Education None Some, but did not complete primary Completed primary Completed secondary Completed tertiary Employment Paid work (part- & full-time) Unemployed Homemaker Retired BMI Underweight (< 18.5) Low risk (Healthy; 18.5e22.9) Moderate risk (23.0e27.4) High risk ( 27.5) Exercise Very physically active Fairly physically active Not very physically active Not at all physically active Smoking No Yes
95% CI
Unaware hypertensives p
OR
95% CI
Uncontrolled hypertensives
p
OR
95% CI
p
Ref. 1.67 0.94
1.11 0.54
2.51 1.64
0.013* 0.836
Ref. 0.67 1.00
0.44 0.55
1.02 1.82
0.062 0.999
Ref. 0.97 2.09
0.64 1.12
1.47 3.87
0.877 0.020*
Ref. 0.72
0.50
1.05
0.092
Ref. 1.01
0.64
1.58
0.982
Ref. 0.87
0.55
1.37
0.536
Ref. 1.23 1.18 0.92
0.90 0.89 0.40
1.67 1.57 2.14
0.193 0.246 0.854
Ref. 1.69 1.09 1.47
1.23 0.80 0.55
2.30 1.49 3.93
0.001* 0.582 0.445
Ref. 1.36 0.78 1.32
0.95 0.57 0.44
1.94 1.08 4.00
0.093 0.129 0.619
0.38
1.08
0.092
0.73
2.83
0.296
0.62
3.25
0.407
0.93 0.36
2.17 1.19
0.104 0.163
0.54 0.50
1.29 2.25
0.416 0.889
1.01 1.83
2.39 15.90
0.047* 0.002*
1.92 1.27 0.79 0.86
6.73 3.58 2.05 2.26
<.0001* 0.004* 0.318 0.180
0.78 0.72 0.80 0.96
3.50 2.95 3.17 3.72
0.192 0.293 0.184 0.067
0.47 0.67 0.52 0.46
1.90 2.37 1.79 1.60
0.876 0.467 0.905 0.624
0.38 0.71 0.95
3.25 1.83 1.96
0.856 0.590 0.089
0.18 0.42 0.39
2.75 1.25 0.92
0.618 0.253 0.019*
1.65 0.83 0.88
89.79 2.59 2.17
0.014* 0.192 0.157
0.75 Ref. 1.88 2.14
0.41
1.37
0.350
0.67
2.96
0.360
2.18
0.843
2.64 3.30
< 0.001* 0.001*
0.46 0.49
1.02 1.23
0.065 0.284
0.92 Ref. 1.27 1.19
0.39
1.33 1.39
1.41 Ref. 0.69 0.78
0.84 0.73
1.92 1.93
0.262 0.498
0.54 0.72 0.74 Ref.
0.25 0.35 0.35
1.17 1.45 1.58
0.119 0.352 0.436
2.31 1.82 1.25 Ref.
1.04 0.90 0.57
5.13 3.71 2.74
0.040* 0.098 0.583
0.91 1.01 0.75 Ref.
0.40 0.51 0.36
2.04 2.00 1.57
0.810 0.984 0.445
0.50
1.35
0.431
0.78
2.16
0.313
0.26
0.98
0.042*
0.64 Ref. 1.42 0.66 3.59 2.14 1.27 1.39 Ref. Ref. 1.11 1.14 1.37
Ref. 0.82
1.44 Ref. 0.83 1.06 1.65 1.46 1.59 1.89 Ref. Ref. 0.71 0.73 0.60
Ref. 1.30
1.42 Ref. 1.55 5.40 0.95 1.26 0.96 0.86 Ref. Ref. 12.19 1.46 1.38
Ref. 0.50
* Statistically significant (p < 0.05). BMI ¼ bodyemass index; CI ¼ confidence interval; OR ¼ odds ratio. Odds Ratio was derived using multiple logistic regression analysis.
diseases is not well established and requires further evaluation. Secondly, we also found that those who were smokers were less likely to have uncontrolled hypertension. This finding has been similarly reported by other studies.57,58 In fact, a study in Singapore identified cigarette smoking in males to be inversely related to SBP, with a reduction of 1.3 mmHg in 1.1% of light smokers, 3.8 mmHg in 3.1% of moderate smokers, and 4.6 mmHg in 3.7% of heavy smokers when these individuals were compared to non-smokers.59 The complex relationship between BP levels and smoking has been suggested to be due to the different response of BP to smoking compounds that depends on the type of smoking, its duration, and onset of BP increase. It is believed that chronic smokers tend to have lower BP associated with loss in body weight, as well as the depressant effects of long-term nicotine use.60 Our cross-sectional study had several strengths which include an adequately large sample size with a high response rate of 66% and an inclusion of a representative sample of elderly that includes even the dialect-speaking locals. Self-reported data on all important medical conditions including hypertension were collected from the respective caregiver, if the elderly participant was deemed unable to provide an accurate account by trained interviewers. Standard protocols were administered for the
measurements of height, weight, and BP, with instruments of measurement maintained and calibrated similarly to reduce measurement errors. Participants were also less likely to experience “white coat” hypertension as the BP measurements were carried out by trained lay interviewers approximately an hour into the full survey. Our study was not without limitations. Like all other hypertension studies, our BP measurements were collected on a single visit to ensure cost-effectiveness and minimize respondent burden and attrition. The use of measurements based on one occasion has been known to lead to overestimation of the prevalence of hypertension by up to 17%.61 Our study did not collect any information pertaining to the type and dosage of the antihypertensive medications and the current use of antihypertensive medications is purely self-reported, hence lacking verification, and limiting our understanding on the possible reasons for lack of optimal BP control in treated hypertensives. We also did not include any other laboratory measurements in this population study, which are useful parameters in obtaining a better understanding of the cardiometabolic risk of our participants. Last but not least, we are unable to draw a conclusion about etiological factors of hypertension and its poor control among the elderly due to the cross sectional design of our study.
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5. Conclusion The prevalence of hypertension among the elderly is high (74.1%). While our study revealed lower proportions of lack of awareness (24.0%) and uncontrolled hypertension (51.1%) compared to other countries, the awareness and control rates are still not ideal. Initiatives to increase awareness and screening are needed, particularly for those individuals with the risk factors that have been identified in this study. Conflicts of interest No potential conflicts of interest were disclosed. Acknowledgments This study was funded by the Ministry of Health, Singapore and the Singapore Millennium Foundation of the Temasek Trust. References 1. World Health Organization. Global status report on noncommunicable diseases 2010. Geneva, Switzerland: World Health Organization; 2011. 2. Nwankwo T, Yoon SS, Burt V, Gu Q. Hypertension among adults in the United States: National Health and Nutrition Examination Survey, 2011e2012. NCHS Data Brief 2013;133:1e8. 3. Whelton PK, He J, Muntner P. Prevalence, awareness, treatment and control of hypertension in North America, North Africa and Asia. J Hum Hypertens 2004;18:545e51. 4. Trenkwalder P, Ruland D, Stender M, Gebhard J, Trenkwalder C, Lydtin H, et al. Prevalence, awareness, treatment and control of hypertension in a population over the age of 65 years: results from the Starnberg Study on Epidemiology of Parkinsonism and Hypertension in the Elderly (STEPHY). J Hypertens 1994;12: 709e16. 5. Vasan RS, Beiser A, Seshadri S, Larson MG, Kannel WB, D'Agostino RB, et al. Residual lifetime risk for developing hypertension in middle-aged women and men: The Framingham Heart Study. JAMA 2002;287:1003e10. 6. O'Donnell CJ, Kannel WB. Cardiovascular risks of hypertension: lessons from observational studies. J Hypertens Suppl 1998;16:S3e7. 7. Muntner P, Davis BR, Cushman WC, Bangalore S, Calhoun DA, Pressel SL, et al. Treatment-resistant hypertension and the incidence of cardiovascular disease and end-stage renal disease: results from the antihypertensive and lipidlowering treatment to prevent heart attack trial (ALLHAT). Hypertension 2014;64:1012e21. 8. Takechi H. Hypertension as a risk factor of dementia and cognitive decline in the elderly. Nihon Ronen Igakkai Zasshi 2007;44:433e6 [In Japanese, English abstract]. 9. Forette F, Boller F. Hypertension and the risk of dementia in the elderly. Am J Med 1991;90(3A):S14e19. 10. Long J, Duan G, Tian W, Wang L, Su P, Zhang W, et al. Hypertension and risk of depression in the elderly: a meta-analysis of prospective cohort studies. J Hum Hypertens 2014. http://dx.doi.org/10.1038/jhh.2014.112 [Epub ahead of print]. 11. Tel H. Anger and depression among the elderly people with hypertension. Neurol Psychiat BR 2013;19:109e13. 12. Roberts RL, Small RE. Cost of treating hypertension in the elderly. Curr Hypertens Rep 2002;4:420e3. 13. Heidenreich PA, Trogdon JG, Khavjou OA, Butler J, Dracup K, Ezekowitz MD, et al. Forecasting the future of cardiovascular disease in the United States: a policy statement from the American Heart Association. Circulation 2011;123: 933e44. 14. World Health Organization, Hypertension control. Report of a WHO Expert Committee. World Health Organ Tech Rep Ser 1996;862:1e83. 15. Hall WD. Risk reduction associated with lowering systolic blood pressure: review of clinical trial data. Am Heart J 1999;138:225e30. 16. Amery A, Birkenhager W, Brixko P, Bulpitt C, Clement D, Deruyttere M, et al. Mortality and morbidity results from the European Working Party on High Blood Pressure in the Elderly trial. Lancet 1985;1:1349e54. 17. Staessen JA, Fagard R, Thijs L, Celis H, Arabidze GG, Birkenhager WH, et al. Randomised double-blind comparison of placebo and active treatment for older patients with isolated systolic hypertension. The Systolic Hypertension in Europe (Syst-Eur) Trial Investigators. Lancet 1997;350:757e64. 18. Staessen JA, Gasowski J, Wang JG, Thijs L, Den Hond E, Boissel JP, et al. Risks of untreated and treated isolated systolic hypertension in the elderly: metaanalysis of outcome trials. Lancet 2000;355:865e72. 19. Singapore Department of Statistics. Population Trends 2014. Singapore, Republic of Singapore: Ministry of Trade and Industry; 2009.
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20. van Rossum CT, van de Mheen H, Witteman JC, Hofman A, Mackenbach JP, Grobbee DE. Prevalence, treatment, and control of hypertension by sociodemographic factors among the Dutch elderly. Hypertension 2000;35:814e21. 21. Kalavathy MC, Thankappan KR, Sarma PS, Vasan RS. Prevalence, awareness, treatment and control of hypertension in an elderly community-based sample in Kerala, India. Natl Med J India 2000;13:9e15. 22. Hypertension Study Group. Prevalence, awareness, treatment and control of hypertension among the elderly in Bangladesh and India: a multicentre study. Bull World Health Organ 2001;79:490e500. 23. Stevens J, Gautman SP, Keil JE. Body mass index and fat patterning as correlates of lipids and hypertension in an elderly, biracial population. J Gerontol 1993;48: M249e54. 24. Stewart KJ, Bacher AC, Turner KL, Fleg JL, Hees PS, Shapiro EP, et al. Effect of exercise on blood pressure in older persons: a randomized controlled trial. Arch Intern Med 2005;165:756e62. 25. Huynh QL, Reid CM, Chowdhury EK, Huq MM, Billah B, Wing LM, et al. Prediction of Cardiovascular and All-Cause Mortality at 10 Years in the hypertensive aged population. Am J Hypertens 2015;28:649e56. 26. Subramaniam M, Chong SA, Vaingankar J, Abdin E, Chua BY, Chua HC, et al. Prevalence of dementia in people aged 60 years and above: results from the WiSE study. J Alzheimers Dis 2015;45:1127e38. 27. WHO Expert Consultation. Appropriate body-mass index for Asian populations and its implications for policy and intervention strategies. Lancet 2004;363: 157e63. 28. Chobanian AV, Bakris GL, Black HR, Cushman WC, Green LA, Izzo JL, et al. Seventh report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure. Hypertension 2003;42: 1206e52. 29. Malhotra R, Chan A, Malhotra C, Østbye T. Prevalence, awareness, treatment and control of hypertension in the elderly population of Singapore. Hypertens Res 2010;33:1223e31. 30. Lloyd-Sherlock P, Beard J, Minicuci N, Ebrahim S, Chatterji S. Hypertension among older adults in low- and middle-income countries: prevalence, awareness and control. Int J Epidemiol 2014;43:116e28. 31. Manton KG. The global impact of noncommunicable diseases: estimates and projections. World Health Stat Q 1988;41:255e66. 32. Department of Statistics Singapore. Population Trends 2013. Available at: http://www.singstat.gov.sg. [accessed 25.1.15]. 33. Pereira M, Lunet N, Azevedo A, Barros H. Differences in prevalence, awareness, treatment and control of hypertension between developing and developed countries. J Hypertens 2009;27:963e75. 34. Huxley R, James WP, Barzi F, Patel JV, Lear SA, Suriyawongpaisal P, et al. Ethnic comparisons of the cross-sectional relationships between measures of body size with diabetes and hypertension. Obes Rev 2008;9(Suppl. 1):53e61. 35. Ibrahim MM, Damasceno A. Hypertension in developing countries. Lancet 2012;380:611e9. 36. Kearney PM, Whelton M, Reynolds K, Muntner P, Whelton PK, He J. Global burden of hypertension: analysis of worldwide data. Lancet 2005;365: 217e23. 37. Yadav G, Chaturvedi S, Grover VL. Prevalence, awareness, treatment and control of hypertension among the elderly in a resettlement colony of Delhi. Indian Heart J 2008;60:313e7. 38. Kannel WB, Gordan T. Evaluation of cardiovascular risk in the elderly: the Framingham study. Bull N. Y Acad Med 1978;54:573e91. 39. Pinto E. Blood pressure and ageing. Postgrad Med J 2007;83:109e14. 40. Masuo K, Mikami H, Ogihara T, Tuck ML. Weight gain-induced blood pressure elevation. Hypertension 2000;35:1135e40. 41. Grotto I, Huerta M, Sharabi Y. Hypertension and socioeconomic status. Curr Opin Cardiol 2008;23:335e9. 42. Duncan BB, Schmidt MI, Achutti AC, Polanczyk CA, Benia LR, Maia AA. Socioeconomic distribution of noncommunicable disease risk factors in urban Brazil: ^ rto Alegre. Bull Pan Am Health Organ 1993;27:337e49. the case of Po 43. Minh HV, Byass P, Chuc NT, Wall S. Gender differences in prevalence and socioeconomic determinants of hypertension: findings from the WHO STEPs survey in a rural community of Vietnam. J Hum Hypertens 2006;20:109e15. 44. Saeed AA, Al-Hamdan NA, Bahnassy AA, Abdalla AM, Abbas MA, Abuzaid LZ. Prevalence, Awareness, Treatment, and Control of Hypertension among Saudi Adult Population: a National Survey. Int J Hypertens 2011;2011:174135. 45. Kiau BB, Kau J, Nainu BM, Omar MA, Saleh M, Keong YW, et al. Prevalence, awareness, treatment and control of Hypertension among the elderly: the 2006 National Health and Morbidity Survey III in Malaysia. Med J Malaysia 2013;68: 332e7. 46. Ke L, Ho J, Feng J, Mpofu E, Dibley MJ, Li Y, et al. Prevalence, Awareness, Treatment and Control of Hypertension in Macau: results from a crosssectional epidemiological study in Macau, China. Am J Hypertens 2015;28: 159e65. 47. Shirani S, Kelishadi R, Sarrafzadegan N, Khosravi A, Sadri G, Amani A, et al. Awareness, treatment and control of hypertension, dyslipidaemia and diabetes mellitus in an Iranian population: the IHHP study. East Mediterr Health J 2009;15:1455e63. 48. Awobusuyi J, Adebola A, Ajose F. Prevalence and socio-demographic profile of hypertensive patients in a Nigerian general out-patients' department. Internet J Third World Med 2012;10:1.
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49. Sheng CS, Liu M, Kang YY, Wei FF, Zhang L, Li GL, et al. Prevalence, awareness, treatment and control of hypertension in elderly Chinese. Hypertens Res 2013;36:824e8. 50. Elperin DT, Pelter MA, Deamer RL, Burchette RJ. A large cohort study evaluating risk factors associated with uncontrolled hypertension. J Clin Hypertens 2014;16:149e54. 51. Umberson D. Gender, marital status and the social control of health behavior. Soc Sci Med 1992;34:907e17. 52. Lewis MA, Rook KS. Social control in personal relationships: impact on health behaviors and psychological distress. Health Psychol 1999;18:63e71. 53. Logan AG. Hypertension in aging patients. Expert Rev Cardiovasc Ther 2011;9: 113e20. 54. Grossman E, Messerli FH. Hypertension and diabetes. Adv Cardiol 2008;45: 82e106. 55. Weycker D, Nichols GA, O'Keeffe-Rosetti M, Edelsberg J, Vincze G, Khan ZM, et al. Excess risk of diabetes in persons with hypertension. J Diabetes Complications 2009;23:330e6.
56. Gress TW, Nieto FJ, Shahar E, Wofford MR, Brancati FL. Hypertension and antihypertensive therapy as risk factors for type 2 diabetes mellitus. N Engl J Med 2000;342:905e12. 57. Tonstad S, Furu K, Rosvold EO, Skurtveit S. Determinants of control of high blood pressure. The Oslo Health Study 2000e2001. Blood Press 2004;13:343e9. 58. Berglund G, Wilhelmsen L. Factors related to blood pressure in a general population sample of Swedish men. Acta Med Scand 1975;198:291e8. 59. Hughes K, Leong WP, Sothy SP, Lun KC, Yeo PP. Relationships between cigarette smoking, blood pressure and serum lipids in the Singapore general population. Int J Epidemiol 1993;22:637e43. 60. Leone A. Does Smoking Act as a Friend or Enemy of Blood Pressure? Let Release Pandora's Box. Cardiol Res Pract 2011;2011:264894. 61. Armitage P, Fox W, Rose GA, Tinker CM. The variability of measurements of casual blood pressure. II. Survey experience. Clin Sci 1966;30:337e44.
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Original article
Hypertension and its associated risks among Singapore elderly residential population Lee Seng Esmond Seow, BA *, Mythily Subramaniam, MBBS, MHSM, Edimansyah Abdin, PhD, Janhavi Ajit Vaingankar, MSc, Siow Ann Chong, MBBS, MMed, MD Research Division, Institute of Mental Health, Singapore
a r t i c l e i n f o
a b s t r a c t
Article history: Received 12 February 2015 Received in revised form 29 April 2015 Accepted 5 May 2015 Available online 15 June 2015
Background: Studies have shown hypertension to be a common health problem among the elderly. The prevalence, awareness, treatment, and control of hypertension, along with their sociodemographic and health-related correlates were established in a national cross-sectional epidemiological study of the elderly in Singapore. The associations between hypertension and select medical risks were also investigated. Methods: Data was collected from 2488 randomly selected elderly ( 60 years) as part of the Well-being of the Singapore Elderly (WiSE) study that involved face-to-face surveys and physical examination. Sitting blood pressure (BP) was measured twice with a 1 minute interval and averaged. Hypertension was defined by a systolic blood pressure (SBP) 140 mmHg, and/or a diastolic blood pressure (DBP) 90 mmHg, and/or current treatment with anti-hypertensive medication. Results: The prevalence of hypertension in this population was 74.1%. The rate of hypertension was associated with older age, lower education, and higher body mass index (BMI). Those who were Malay, retired and very physically active were more likely to be unaware of being hypertensive. An age of 85 years, being unemployed, widowed or divorced/separated, and being a non-smoker were associated with uncontrolled hypertension. Those with hypertension were also more likely to report a diagnosis of diabetes. Conclusion: The proportion of elderly with hypertension is high in this Asian population. What is of concern is the substantial proportion of undetected cases. This highlights the need for effective health screening among the elderly. Optimal control of BP in those diagnosed with hypertension is also a cause for concern, as identified in our study. Copyright © 2015, Asia Pacific League of Clinical Gerontology & Geriatrics. Published by Elsevier Taiwan LLC. Open access under CC BY-NC-ND license.
Keywords: awareness control epidemiology hypertension prevalence treatment
1. Introduction Hypertension is a chronic health problem that involves the primary elevation of systemic blood pressure (BP), otherwise known as high BP. It is a global public health issue that affects approximately 1 billion people worldwide in both developed and developing countries.1 Prevalence of hypertension increases with age and hence the elderly tend to have the highest prevalence within a particular population,2,3 reaching as high as 60e80% in developed nations.2,4
* Corresponding author. Research Division, Institute of Mental Health, Buangkok Green Medical Park, 10 Buangkok View, Singapore 539747, Singapore. E-mail address: [email protected] (L.S.E. Seow).
The Framingham Heart Study found that the residual lifetime risks of developing hypertension through to the age of 80 years for men and women who were normotensive at age 55 years are 93% and 91% respectively. This means that more than 90% of individuals who are free from hypertension at 55 years of age will eventually develop it during their remaining life span.5 As the world population ages progressively along with a concomitant increase in life expectancy, the issue of hypertension among the elderly has become a further cause for concern. Hypertension is a widely recognised major risk factor for cardiovascular disease such as stroke and myocardial infarction, as well as for chronic kidney diseases and congestive heart failure among men and women,6,7 making it the leading cause of morbidity and mortality among the elderly. In addition, it has been suggested that hypertension increases the risk of dementia
http://dx.doi.org/10.1016/j.jcgg.2015.05.002 2210-8335/Copyright © 2015, Asia Pacific League of Clinical Gerontology & Geriatrics. Published by Elsevier Taiwan LLC. Open access under CC BY-NC-ND license.
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and cognitive decline among the elderly.8,9 The evidence supporting the relationship between hypertension and depression, however, remains controversial.10,11 Generally, it was reported that the elderly have higher expenditures per capita for hypertension and related diseases.12 The annual cardiovascular costs (including health care services, medication, and missed days of work) associated with hypertension in the United States for people aged 65e79 years are projected to increase by 238%, from $135 billion to $457 billion per year, from 2010 to 2030.13 Better control of hypertension among the elderly requires an increase in awareness among the population and improved effectiveness of pharmacological and non-pharmacological interventions.14 Early detection and treatment aids in minimizing the medical care costs associated with hypertension and the other diseases for which people with hypertension are at increased risk. Randomized, controlled clinical trials have demonstrated significant clinical benefits in treating hypertension among the elderly.15e17 In a metaanalysis involving 15,693 elderly participants with isolated systolic hypertension in eight clinical trials against placebo, the risk of stroke was reduced by 30%, coronary heart disease events by 23%, all cardiovascular complications by 26%, and cardiovascular mortality by 18% upon active drug therapy.18 Singapore has an aging population with those aged 65 years making up 11% of the residential population in 2014.19 Many studies have identified the effects of demographic and lifestyle factors such as gender, age, socioeconomic status,20,21 smoking,21,22 body mass index (BMI),23 exercise22,24 and alcohol consumption25 on BP among the elderly. However, such characteristics are not uniform across countries due to key differences in demographics indicators (e.g., ethnicity) and level of socioeconomic deprivation. Hence, epidemiological analysis needs to be conducted in the local context for better planning and management of hypertension in any population. In this study, our aims were to: (1) investigate the prevalence, awareness, treatment, and adequacy of control of hypertension; (2) examine their respective sociodemographic and health-related correlates; and (3) investigate the association between hypertension and select lifetime medical conditions (self-reported) among the elderly population in Singapore. 2. Methods 2.1. Study overview Data was collected as part of the Well-Being of the Singapore Elderly (WiSE) study, a cross-sectional household survey involving face-to-face interview and physical examination conducted from October 2012 to December 2013. The door-to-door visits were preceded by an extensive training program for the field interviewers who were individually assessed for their proficiency and skill in performing the necessary procedures. Participants were given an inconvenience fee upon completion of the survey. The study was approved by the relevant ethics committees in Singapore i.e. the National Healthcare Group, Domain Specific Review Board, and the SingHealth Centralised Institutional Review Board. The study methodology has been described in detail in a prior article.26 2.2. Study participants The respondents in the study were Singapore residents (including Singapore citizens and permanent residents) aged 60 years who were living in Singapore. They were randomly selected from a national database that maintains the names, sociodemographic information such as age, gender, ethnicities, and household addresses of all residents. Efforts were made to follow up on residents who were admitted to, or residing in a hospital or nursing home during the course of the study. Residents who were living
outside the country and those not contactable due to incomplete or incorrect addresses were excluded from the study. Prior to participation, written informed consent was obtained from all respondents and in the case of participants who were unable to provide informed consent, a written informed consent was taken from their legally acceptable representative or next of kin. To increase the precision of subgroup estimation, a disproportionate stratified sampling (by age group and ethnicity) was planned, where the three main ethnic groupsdChinese, Malay, and Indiandwere sampled in proportions of approximately 40%, 30%, and 30% respectively. Individuals aged 75 years were also over-sampled. Sociodemographic information including age, gender, ethnicity, marital status, education, employment status, as well as level of physical activity and smoking status were collected using a structured questionnaire. The interviewers also measured the height and weight of each respondent to obtain their BMI for risk assessment of cardiovascular disease. The suggested categories based on Asian populations27 are as follows: (1) underweight (< 18.5 kg/m3); (2) increasing, but acceptable risk of cardiovascular disease (18.5e23.0 kg/m3); (3) increased risk (23.0e27.5 kg/m3); and (4) high risk (> 27.5 kg/m3). 2.3. Measurement of BP During the course of the visit, resting BP was measured twice, with a 1 minute interval, by the trained interviewers using an electronic sphygmomanometer (Omron HEM-7211; Omron Healthcare). Participants were advised to relax in a sitting position, with their left elbow raised to the heart level and were asked to abstain from eating, drinking alcohol or caffeinated beverages, exercising or smoking for at least 30 minutes prior to their BP measurement. The mean of the two readings was used to define the systolic (SBP) and diastolic (DBP) blood pressure. 2.4. Definitions Hypertension was defined as having a SBP 140 mmHg, a DBP 90 mmHg, and/or undergoing current treatment with antihypertensive medication. This definition excludes hypertensive individuals who have attained a BP level in the normotensive range by non-pharmacological means.28 Awareness of hypertension was defined as a prior diagnosis by a doctor. Treatment of hypertension was defined as the current pharmacological treatment initiated by the doctors for lowering elevated BP. Control of hypertension was defined as having a current SBP < 140 mmHg and DBP < 90 mmHg associated with the pharmacological treatment. 2.5. Statistical analyses All estimates were weighted to adjust for over-sampling and post-stratified for age and ethnicity distributions between the survey sample and the Singapore resident population in 2011. Mean and standard error were calculated for BP values, and frequencies and percentages for all other categorical variables. We also examined the mean and distribution of BP classes, as defined by the Joint National Committee on Prevention, Detection, Evaluation and Treatment of High Blood Pressure (JNC-7)28, in the study sample across age, gender, and ethnicity. For the purpose of the study, a series of multiple logistic regression analyses were performed to study the impact of select sociodemographic and health-related factors on the prevalence of hypertension. We used hypertension status as the main outcome variable, with age, gender, ethnicity, marital status, education, employment status, BMI, exercise, and smoking as predictor variables. Respondents' awareness, treatment and control of hypertension were also investigated. The association between
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hypertension and the self-reporting of lifetime heart problems (heart attack, angina, heart failure, and valve disease), diabetes, transient ischemic attacks (TIAs), and stroke were also established after controlling for confounding variables. Standard errors (SE) and significance tests were determined using the Taylor series linearization method. Multivariate significance was evaluated using Wald Chi-square test based on designcorrected coefficient varianceecovariance matrices. Statistical significance was set at p < 0.05 using two-sided tests. All statistical analyses were carried out using the SAS version 9.2 (SAS Institute Inc., Cary, NC, USA). 3. Results 3.1. Study sample characteristics Of the 2565 respondents interviewed for the WiSE study, 2488 individuals agreed to BP measurements. Table 1 presents the sociodemographic and health-related characteristics of the elderly participants. 3.2. Mean BP levels and JNC-7 BP classification (across age, gender, and ethnicity) Table 2 presents the distribution of BP among the respondents according to the recommendation by JNC-7. Mean BP (± SE) was Table 1 Characteristics of the study participants (n ¼ 2488). Variable Age group (y) 60e74 75e84 85þ Gender Men Women Ethnicity Chinese Malay Indian Others Marital status Never married Married/cohabiting Widowed Divorced/separated Education None Some, but did not complete primary Completed primary Completed secondary Completed tertiary Employment Paid work (part-time & full-time) Unemployed Homemaker Retired BMI Underweight (< 18.5) Low risk (Healthy range; 18.5e22.9) Moderate risk (23.0e27.4) High risk ( 27.5) Exercise Very physically active Fairly physically active Not very physically active Not at all physically active Smoking No Yes BMI ¼ body mass index.
n
Unweighted %
Weighted %
1461 652 375
58.7 26.2 15.1
75.4 19.4 5.2
1098 1390
44.1 55.9
44.3 55.7
994 714 745 35
40.0 28.7 29.9 1.4
83.7 9.0 5.9 1.4
134 1452 795 105
5.4 58.4 32.0 4.2
8.1 64.2 22.2 5.6
493 588 627 511 257
19.9 23.7 25.3 20.6 10.4
16.4 23.5 25.0 22.6 12.5
682 32 775 971
27.7 1.3 31.5 39.5
34.2 1.6 26.1 38.1
142 629 887 582
6.3 28.1 39.6 26.0
5.5 32.2 42.0 20.4
344 1329 453 349
13.9 53.7 18.3 14.1
16.8 59.6 17.1 6.4
2251 233
90.6 9.4
90.3 9.7
127
141.4 ± 0.6/75.2 ± 0.3 mmHg. DBP was found to decline with age and was lower among women. Malays had the highest SBP and DBP levels. Around 31.7% of the elderly had current stage 1 or 2 hypertension; the proportion increased with age, did not vary with gender, and was highest among those of Malay ethnicity in Singapore. 3.3. Prevalence of hypertension and of awareness, treatment, and control of hypertension Of the 2488 respondents, nearly three-quarters (74.1%) of the elderly population had hypertension. Among those who had hypertension, slightly more than three-quarters (76.0%) were aware of their condition. A majority of those who were aware of their elevated BP were also on treatment. Nearly half of the treated hypertensive subjects satisfied JNC-7 recommendations for adequate BP control. Thirty-eight respondents did not currently have hypertension despite not receiving pharmacological treatment following prior diagnosis by a doctor. Data on the awareness, treatment, and control of hypertensive participants in our study sample are displayed in Figure 1 and Table 3. 3.4. Correlates of hypertension and of awareness and control of hypertension Based on data presented in Figure 1, two at-risk groups with elevated BP were identifieddthose who were unaware that they had hypertension and those who had suboptimal BP control despite treatment. Those who were untreated upon diagnosis (n ¼ 56) were excluded as their number was too small for any conclusive statistical analyses or meaningful comparison. The odds of hypertension were significantly higher among elderly participants aged 75e84 years compared to those aged 60e74 years (Table 4). Those who did not have any education or did not complete primary education and those with moderate or high risk BMI were more likely to have hypertension. The hypertensive elderly who were unaware of their condition were more likely to be Malays (compared to Chinese) and to be very physically active. Those who were retired were less likely to be unaware that they have hypertension than those doing paid work (part-time or fulltime). Elderly with suboptimal BP control despite treatment were more likely to be in the oldest age group (85þ years) and unemployed. In addition, they were more likely to be widowed or divorced/separated than married or cohabiting. Those who smoked were more likely to have their BP controlled with treatment. 3.5. Association of hypertension with reporting of lifetime medical conditions After controlling for age, education and BMI (factors associated with prevalence of hypertension), elderly with hypertension were found to have higher odds of reporting lifetime diabetes [odds ratio (OR) of 1.70, 95% confidence interval (CI) of 1.19e2.43], compared to those without hypertension. No significant relationship was found between hypertension and other lifetime conditions such as heart problems, TIAs, and stroke. 4. Discussion The WiSE study is the second to provide information on the prevalence, awareness, treatment, and control of hypertension along with their relevant correlates among the local elderly. The Singapore Social Isolation, Health, and Lifestyle Survey (SIHLS) conducted in 200929 was the first to present a comprehensive picture of hypertension management among the Singapore elderly.
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Table 2 Mean systolic and diastolic blood pressure, and distribution of blood pressure classes by the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure; overall and by age, gender, and ethnicity. BP levels (mmHg), mean (SE)
All Age group (y) 60e74 75e84 85þ Gender Men Women Ethnicity Chinese Malay Indian Others
BP categories based on JNC-7. Weighted row, n (%)
SBP
DBP
Normal
HigheNormal
Stage 1
Stage 2
141.4 (0.6)
75.2 (0.3)
316 (13.4)
1322 (54.9)
619 (23.6)
231 (8.1)
140.8 (0.7) 143.8 (1.1) 142.6 (1.6)
76.5 (0.4) 72.2 (0.6) 68.7 (0.8)
187 (13.9) 66 (10.9) 63 (16.3)
840 (56.8) 330 (51.5) 152 (40.6)
337 (22.7) 178 (25.6) 104 (28.3)
141.0 (0.8) 141.8 (0.8)
76.8 (0.5) 74.0 (0.4)
152 (12.6) 164 (14.1)
588 (55.8) 734 (54.2)
276 (24.5) 343 (22.9)
140.9 148.1 139.9 138.6
74.9 78.4 75.5 73.2
138 61 112 5
525 384 397 16
238 185 183 13
(0.7) (0.9) (0.8) (2.7)
(0.4) (0.5) (0.4) (2.4)
(13.9) (7.5) (15.3) (14.9)
(54.9) (56.4) (55.1) (47.1)
(23.1) (26.3) (23.1) (36.5)
97 (6.7) 78 (12.0) 56 (14.8) 82 (7.2) 149 (8.8) 93 84 53 1
(8.2) (9.8) (6.6) (1.6)
BP ¼ blood pressure; DBP ¼ diastolic blood pressure; JNC-7 ¼ Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure; SBP ¼ systolic blood pressure.
The two studies (WiSE and SIHILS) reported prevalence rates of 74.1% and 73.9%, awareness rates of 76.0% and 69.2%, treatment rates of 95.8% and 98.1% and, control rates of 48.9% and 35.4% respectively. In terms of prevalence and treatment rates, the findings were almost comparable. The awareness and control rates were higher in this study by 6.8% and 13.5% respectively. As reported by Malhotra et al29, Singapore has reported a higher prevalence of hypertension among the elderly population compared to most studies conducted in other countries but the awareness and treatment rates were also higher. In line with these findings, the World Health Organization's Study on Global Aging and Adult Health (SAGE)30 reported mean prevalence, awareness, control and treatment efficacy rates of 52.9%, 48.3%, 10.2%, and 26.3% respectively, across six countries, namely China, Ghana, India, Mexico, the Russian Federation, and South Africa. With the average life span extending worldwide, people are increasingly developing diseases of old age including hypertension.31 With Singapore being one of the fastest aging populations and its life expectancy rate at a high of 82.3 years in 2013,32 the high prevalence of hypertension among the elderly is not surprising. The prevalence or risk of hypertension also tends to be higher in more developed countries,33 as well as among the Asian compared to the Western populations at any given level of BMI, waist circumference, and waist-to-hip ratio.34 Lastly, other possible reasons for the variation in prevalence rate among countries could be due to difference in demographics such as ethnic makeup as well as different lifestyles factors (e.g., diet and physical activity). High salt intake may have contributed to the high prevalence observed in the study. The National Nutrition Survey in 2010
revealed that eight out of ten Singaporeans exceed their recommended daily salt intake, with the average person consuming 8.3 g daily which is 60% above recommended level of 5 g per day for adults. The rates of awareness, treatment, and control tend to be higher in developed countries including Singapore, possibly due to better management of hypertension cases compared to developing countries which have high illiteracy rates, poor access to health facilities, poverty, and high costs of drugs.33,35 In addition, continuous nationwide efforts by health care organizations such as the Health Promotion Board in promoting awareness of chronic diseases and healthy lifestyles have played an essential role in the higher awareness and control of hypertension among Singaporeans. The Health Promotion Board was established in 2001 by the Ministry of Health of Singapore to act as the main driver for national health promotion and disease prevention programs, with its vision being to build a nation of “healthy people”. In our current study, all non-modifiable sociodemographic and modifiable health-related factors including age, ethnicity, marital status, education, employment status, BMI, exercise, and smoking, but excluding gender, were associated with hypertension prevalence, awareness, and control. The pattern of association between hypertension prevalence and gender varied across countries but overall worldwide data revealed no significant gender difference.36 Most of our findings were similar to previous studies. We found hypertension to be associated with older age and higher BMI, consistent with a number of other studies.4,21,22,29,37 SBP tends to show continuous increase until the 8th decade of life.38 This is expected as advancing age is associated with a degenerative process
Figure 1. Hypertension and its awareness, treatment and control among Singapore elderly. Data are presented as n (weighted %).
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129
Table 3 Weighted prevalence of hypertension and of elderly with hypertension who were unaware, treated or uncontrolled. With hypertensiona Age group (y) 60e74 75e84 85þ Gender Men Women Ethnicity Chinese Malay Indian Others Marital status Never married Married/cohabiting Widowed Divorced/separated Education None Some, but did not complete primary Completed primary Completed secondary Completed tertiary Employment Paid work (part- & full-time) Unemployed Homemaker Retired BMI Underweight (< 18.5) Low risk (Healthy; 18.5e22.9) Moderate risk (23.0e27.4) High risk ( 27.5) Exercise Very physically active Fairly physically active Not very physically active Not at all physically active Smoking No Yes
Unaware hypertensivesa
Treated hypertensivesa
Uncontrolled hypertensivesa
1089 (71.3) 553 (85.0) 277 (74.2)
788 (73.6) 436 (82.9) 216 (80.8)
730 (95.2) 411 (97.4) 206 (96.0)
364 (50.0) 218 (51.5) 124 (61.7)
824 (74.6) 1095 (73.7)
595 (74.7) 845 (77.1)
557 (96.8) 790 (95.0)
279 (49.4) 427 (52.3)
741 575 578 25
(73.3) (81.2) (76.8) (69.6)
580 400 441 19
(77.0) (69.1) (75.0) (73.9)
537 371 420 537
(95.8) (94.1) (97.7) (95.8)
280 215 200 11
(50.6) (57.9) (45.6) (56.2)
91 1107 648 72
(60.9) (74.5) (81.0) (62.7)
64 815 511 49
(66.9) (75.4) (81.1) (71.3)
58 762 483 44
(92.5) (95.8) (98.0) (89.7)
31 359 285 31
(54.3) (46.0) (58.4) (76.4)
408 467 482 385 171
(85.3) (78.5) (70.0) (71.6) (64.0)
302 359 360 276 138
(77.7) (76.9) (75.1) (71.3) (82.6)
285 330 343 256 128
(96.8) (93.5) (98.4) (94.2) (96.5)
148 190 179 130 57
(50.4) (55.8) (50.8) (47.7) (49.2)
488 21 643 750
(68.4) (75.0) (77.4) (77.6)
312 15 504 597
(67.7) (76.6) (78.5) (80.9)
284 13 475 564
(94.7) (97.8) (97.5) (95.4)
135 10 264 289
(43.5) (89.5) (53.6) (52.1)
93 449 714 486
(64.8) (66.3) (78.1) (81.2)
59 310 548 380
(67.7) (71.6) (78.8) (75.3)
51 291 508 366
(93.5) (95.3) (96.0) (97.6)
25 154 269 195
(45.8) (48.6) (53.7) (51.8)
247 1031 363 271
(69.3) (73.9) (77.7) (81.5)
169 761 286 221
(69.5) (74.8) (82.1) (87.3)
150 717 272 205
(89.6) (97.5) (95.3) (95.5)
75 381 141 107
(48.8) (52.2) (48.3) (52.8)
1753 (74.7) 164 (69.5)
1348 (77.0) 90 (66.2)
1263 (95.6) 82 (97.8)
671 (52.1) 33 (39.9)
BMI ¼ bodyemass index. a Data are presented as n (weighted %).
that involves the thickening and loss of elasticity of arteries, hence contributing to high BP.39 Being overweight and obese is known to stimulate sympathetic nervous system activity, fasting plasma insulin, and leptin which can lead to elevated BP levels.40 Our study also found hypertension to be inversely associated with education where individuals who did not have any formal education or had not completed primary education were more likely to have hypertension, compared to those who had tertiary education. Low education has been associated with elevated levels of BP and related cardiovascular diseases, possibly due to the lack of awareness of hypertension prevention and control, and of adherence to medical treatment.41 The inverse relationship between educational attainment and incidence of hypertension was also observed in other hypertension studies in Brazil,42 Vietnam43, and Saudi Arabia.44 In terms of awareness of hypertension, the Malays had significantly lower rate of awareness compared to the Chinese and this finding is consistent with other studies.29,45 Those who were retired were less likely to be unaware of their condition,46,47 since they tend to have more time to focus on their health and seek early management of adverse health conditions. Unemployment was associated with a higher risk of uncontrolled hypertension. Being unemployed or having a low income could possibly have a negative impact on the ability of individuals to purchase prescribed
antihypertensive drugs and thus, lead to low medication compliance.48 Those who were widowed or divorced/separated (no longer partnered) were more likely to have uncontrolled hypertension.20,49,50 Individuals who had close daily contact with a spouse or partner tend to find themselves adopting health promoting behavior through social direct control such as encouraging, monitoring, reminding, and even threatening.51,52 Older individuals in our study also had higher rate of uncontrolled hypertension since BP usually gets more difficult to control with increasing age.53 Finally, our study revealed that elderly with hypertension were at higher risk of diabetes which is supported by a vast amount of research.54e56 A number of interesting findings were noted. Firstly, our results showed that elderly who were very physically active were more likely to be unaware of their hypertensive condition. This finding is contrary to what was found in another study.44 Possible explanations would be that our elderly respondents might have overestimated their level of physical activity (e.g., regarding regular low-intensity tai chi or walking as high physical activities) or that those with high physical activity levels might have been overconfident about their health status, and thus forgone the essential visits to the doctors for medical screenings. Nonetheless, the association of high physical activity leading to awareness of chronic
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Table 4 Sociodemographic and health-related correlates of hypertension, unawareness, and lack of blood pressure control among treated hypertensives. With hypertension OR Age group (y) 60e74 75e84 85þ Gender Men Women Ethnicity Chinese Malay Indian Others Marital status Never married Married/cohabiting Widowed Divorced/separated Education None Some, but did not complete primary Completed primary Completed secondary Completed tertiary Employment Paid work (part- & full-time) Unemployed Homemaker Retired BMI Underweight (< 18.5) Low risk (Healthy; 18.5e22.9) Moderate risk (23.0e27.4) High risk ( 27.5) Exercise Very physically active Fairly physically active Not very physically active Not at all physically active Smoking No Yes
95% CI
Unaware hypertensives p
OR
95% CI
Uncontrolled hypertensives
p
OR
95% CI
p
Ref. 1.67 0.94
1.11 0.54
2.51 1.64
0.013* 0.836
Ref. 0.67 1.00
0.44 0.55
1.02 1.82
0.062 0.999
Ref. 0.97 2.09
0.64 1.12
1.47 3.87
0.877 0.020*
Ref. 0.72
0.50
1.05
0.092
Ref. 1.01
0.64
1.58
0.982
Ref. 0.87
0.55
1.37
0.536
Ref. 1.23 1.18 0.92
0.90 0.89 0.40
1.67 1.57 2.14
0.193 0.246 0.854
Ref. 1.69 1.09 1.47
1.23 0.80 0.55
2.30 1.49 3.93
0.001* 0.582 0.445
Ref. 1.36 0.78 1.32
0.95 0.57 0.44
1.94 1.08 4.00
0.093 0.129 0.619
0.38
1.08
0.092
0.73
2.83
0.296
0.62
3.25
0.407
0.93 0.36
2.17 1.19
0.104 0.163
0.54 0.50
1.29 2.25
0.416 0.889
1.01 1.83
2.39 15.90
0.047* 0.002*
1.92 1.27 0.79 0.86
6.73 3.58 2.05 2.26
<.0001* 0.004* 0.318 0.180
0.78 0.72 0.80 0.96
3.50 2.95 3.17 3.72
0.192 0.293 0.184 0.067
0.47 0.67 0.52 0.46
1.90 2.37 1.79 1.60
0.876 0.467 0.905 0.624
0.38 0.71 0.95
3.25 1.83 1.96
0.856 0.590 0.089
0.18 0.42 0.39
2.75 1.25 0.92
0.618 0.253 0.019*
1.65 0.83 0.88
89.79 2.59 2.17
0.014* 0.192 0.157
0.75 Ref. 1.88 2.14
0.41
1.37
0.350
0.67
2.96
0.360
2.18
0.843
2.64 3.30
< 0.001* 0.001*
0.46 0.49
1.02 1.23
0.065 0.284
0.92 Ref. 1.27 1.19
0.39
1.33 1.39
1.41 Ref. 0.69 0.78
0.84 0.73
1.92 1.93
0.262 0.498
0.54 0.72 0.74 Ref.
0.25 0.35 0.35
1.17 1.45 1.58
0.119 0.352 0.436
2.31 1.82 1.25 Ref.
1.04 0.90 0.57
5.13 3.71 2.74
0.040* 0.098 0.583
0.91 1.01 0.75 Ref.
0.40 0.51 0.36
2.04 2.00 1.57
0.810 0.984 0.445
0.50
1.35
0.431
0.78
2.16
0.313
0.26
0.98
0.042*
0.64 Ref. 1.42 0.66 3.59 2.14 1.27 1.39 Ref. Ref. 1.11 1.14 1.37
Ref. 0.82
1.44 Ref. 0.83 1.06 1.65 1.46 1.59 1.89 Ref. Ref. 0.71 0.73 0.60
Ref. 1.30
1.42 Ref. 1.55 5.40 0.95 1.26 0.96 0.86 Ref. Ref. 12.19 1.46 1.38
Ref. 0.50
* Statistically significant (p < 0.05). BMI ¼ bodyemass index; CI ¼ confidence interval; OR ¼ odds ratio. Odds Ratio was derived using multiple logistic regression analysis.
diseases is not well established and requires further evaluation. Secondly, we also found that those who were smokers were less likely to have uncontrolled hypertension. This finding has been similarly reported by other studies.57,58 In fact, a study in Singapore identified cigarette smoking in males to be inversely related to SBP, with a reduction of 1.3 mmHg in 1.1% of light smokers, 3.8 mmHg in 3.1% of moderate smokers, and 4.6 mmHg in 3.7% of heavy smokers when these individuals were compared to non-smokers.59 The complex relationship between BP levels and smoking has been suggested to be due to the different response of BP to smoking compounds that depends on the type of smoking, its duration, and onset of BP increase. It is believed that chronic smokers tend to have lower BP associated with loss in body weight, as well as the depressant effects of long-term nicotine use.60 Our cross-sectional study had several strengths which include an adequately large sample size with a high response rate of 66% and an inclusion of a representative sample of elderly that includes even the dialect-speaking locals. Self-reported data on all important medical conditions including hypertension were collected from the respective caregiver, if the elderly participant was deemed unable to provide an accurate account by trained interviewers. Standard protocols were administered for the
measurements of height, weight, and BP, with instruments of measurement maintained and calibrated similarly to reduce measurement errors. Participants were also less likely to experience “white coat” hypertension as the BP measurements were carried out by trained lay interviewers approximately an hour into the full survey. Our study was not without limitations. Like all other hypertension studies, our BP measurements were collected on a single visit to ensure cost-effectiveness and minimize respondent burden and attrition. The use of measurements based on one occasion has been known to lead to overestimation of the prevalence of hypertension by up to 17%.61 Our study did not collect any information pertaining to the type and dosage of the antihypertensive medications and the current use of antihypertensive medications is purely self-reported, hence lacking verification, and limiting our understanding on the possible reasons for lack of optimal BP control in treated hypertensives. We also did not include any other laboratory measurements in this population study, which are useful parameters in obtaining a better understanding of the cardiometabolic risk of our participants. Last but not least, we are unable to draw a conclusion about etiological factors of hypertension and its poor control among the elderly due to the cross sectional design of our study.
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