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Prevalence, awareness, and control of arterial hypertension in Denmark
Journal of the American Society of Hypertension 3(1) (2009) 19 –24
Research Article
Prevalence, awareness, and control of arterial hypertension in Denmark Christel N. Kronborg, MD, PhD, Jesper Hallas, MD, DMSc, and Ib A. Jacobsen, MD, DMSc* Department of Internal Medicine C, Odense University Hospital, Odense, Denmark Manuscript received May 12, 2008 and accepted August 1, 2008
Abstract Hypertension is an important modifiable risk factor for cardiovascular disease. Risk is reduced by reduction of blood pressure (BP). The present survey estimated the prevalence of hypertension, awareness, treatment, and BP control in Denmark. BP was measured three times on one occasion in a representative sample (n ⫽ 7,767) of the Danish population ages 20 to 89 years. Persons with screening BP ⱖ140/90 mm Hg also measured BP at home. Participants with home BP ⱖ135/85 mm Hg in general and ⱖ125/75 mm Hg for patients with diabetes or renal disease were categorized as hypertensive together with those already on antihypertensive treatment. Awareness was registered by questionnaire. Treated patients with BP below relevant limits were categorized as controlled. Age-adjusted prevalence of hypertension was on the basis of screening BP 25.7% and by home BP 22.3%. Seventy-two percent of patients found hypertensive by home BP were aware of it, 64% were treated, and 57% of those treated were controlled by office BP and 68% by home BP. One-fifth of the adult Danish population was found to be hypertensive, Awareness and control of hypertension was better than in most previous reports. Control rates similar to those of clinical trials are achievable in clinical practice. J Am Soc Hypertens 2009;3(1): 19 –24. © 2009 American Society of Hypertension. All rights reserved. Keywords: Epidemiology; antihypertensive therapy; detection; blood pressure.
Introduction High blood pressure (BP) is an important risk to health in all parts of the world. It increases the risk of cardiovascular disease; thus, about two-thirds of cerebrovascular disease and half of ischemic heart disease is attributable to arterial hypertension.1,2 There is ample evidence that the cardiovascular risk in hypertensive patients is reduced significantly by lowering BP, most effectively with the aid of antihypertensive drugs.3 Normalization of BP is not easily achieved, even in controlled trials with optimal motivation both for patients and for treating physicians. The recommended goal of a diaThis study was funded by Apotekerfonden of 1991, The Danish Heart Foundation, The University of Southern Denmark, the County of Funen, and to a smaller extent by Pfizer, Novartis, Boehringer-Ingelheim, Solvay, and Sanofi-Synthelabo. Dr. Hallas has received research Grants from Novartis, Nycomed, and Merck Sharp & Dohme, and fees for teaching from Astra-Zeneca, Nycomed, Pfizer, and the Danish Association of Pharmaceutical Industry. Supplemental Material is available at www.ashjournal.com. *Corresponding author: Ib A. Jacobsen, MD, DMSc, Department of Endocrinology M, Odense University Hospital, DK-5000 Odense, Denmark. Tel: ⫹45 2720313; fax: ⫹45 65919653. E-mail: [email protected]
stolic BP lower than 90 mm Hg is frequently achieved, whereas a systolic BP lower than 140 mm Hg presents a greater problem. The lower goals for hypertensive patients with diabetes and nephropathy are infrequently reached.4 Surveys of antihypertensive treatment in clinical practice have shown even less favorable results.5 A recent analysis estimated that more than one-fourth of the world’s adult population is hypertensive, with considerable variation in prevalence between regions.6 In economically developed countries, only half to two-thirds of the hypertensive population were aware of the diagnosis, fewer than half of them were treated, and less than one-third of hypertensives had their BP controlled by treatment. In economically developing counties, the results are even more dismal.5 The task of today’s health services is to transfer available knowledge of effective antihypertensive treatment from controlled trials to clinical practice. The present survey is a study of the prevalence, awareness, treatment, and control of hypertension in Denmark.
Methods The study was designed as a representative cross-sectional survey of the Danish population. For practical reasons, it was based on a population sample randomly drawn
1933-1711/09/$ – see front matter © 2009 American Society of Hypertension. All rights reserved. doi:10.1016/j.jash.2008.08.001
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Informed Consent All participants have given written consent after oral and written information. The study was approved by the regional ethics committee for Funen and Vejle Counties (VF 20020213) and by the Danish data protection agency.
Statistics
Figure 1. Total number of subjects in the survey.
from a geographic area comprising the city of Odense (the home of The University of Southern Denmark) and three surrounding rural municipalities. The necessary sample size was calculated on the basis of expected prevalence based on data from the National Health and Nutrition Examination Survey III and Inter-99 surveys,7,8 and stratified according to age and gender. A sample of 15,633 persons (Figure 1) stratified in 10year bands, comprising the age range 20 to 89 years and both genders, was randomly drawn from the Central persons register, which contains data on all Danish citizens. The population sample was invited to the hypertension clinic for BP screening. BP was measured in the sitting position by a trained nurse after 5 minutes’ rest and with a standard mercury sphygmomanometer. Initial measurements were performed on both arms, and a further three measurements were performed on the arm with the highest pressure. The mean of the two latest measurements was used as screening BP. Participants with elevated screening BP were asked to measure their BP at home, three times in the morning and three times in the evening for three consecutive days using a validated device after instruction by a trained nurse (A&D UA767; A&D Company Ltd, Tokyo, Japan).9 The mean of home-BP measured on the last two days was used as the home-BP for further analysis. Participants with elevated home-BP and those on current antihypertensive treatment were registered as hypertensives. Screening-BP ⱖ140/90 mm Hg was registered as elevated in general and in cases of diabetes mellitus or nephropathy, participants with BP ⱖ130/80 mm Hg were registered as hypertensives. The corresponding home-BP were ⱖ135/85 mm Hg and ⱖ125/75 mm Hg. Treated participants with home-BP below the relevant limits were registered as controlled. All participants were asked to fill in a questionnaire at the screening center about relevant medical history, other cardiovascular risk factors, and current medication. Participants diagnosed with hypertension had blood and urine samples collected for serum electrolytes, serum creatinine, serum lipids, plasma glucose, and urine albumin excretion.
To ascertain a possible selection bias in the attendance of the survey, data on use of certain cardiovascular drugs and of cardiovascular diagnoses from previous inpatient contacts of attendees and nonattendees were compared (see Supplemental text available at Ashjournal.com). To account for a possible nonrepresentativeness in our source population, we retrieved data on physician contacts, cardiovascular morbidity, and socioeconomic status in the four participating municipalities in our study and in Denmark as a whole (see Supplemental text). Statistical analysis was performed with SPSS version 13.0 for Windows (SPSS Inc, Chicago, IL). Prevalence is reported with 95% confidence intervals. Age-adjusted prevalences were calculated on the basis of the Danish population in 2006.
Results The comparison of socioeconomic status and health-related characteristics of the source population with the Danish population as a whole showed only minor differences (see Supplemental Tables 1 and 2 available at Ashjournal. com). Fifty percent of the invited population sample attended the survey. Comparison of attendees and nonattendees on the basis of previous hypertension-related diagnoses, current medication, and socioeconomic variables showed the two groups to be comparable (see Supplemental Tables 3 and 4). Thus, the examined population sample was found to be representative of the general Danish population. Based on screening-BP, 1104 or 14.4% (13.6 to 15.1) of the participants were hypertensive, whereas 971 or 12.6% (11.9 to 13.4) were hypertensive on the basis of home-BP. The age-specific prevalence of hypertension based on home-BP varied markedly from 1% in the 20- to 29-year-old group to 69% in the 80- to 89-year-old group (Figure 2; Table 1). There was no significant difference between the prevalence in men and women, and all results are accordingly presented by age alone. The frequency of other relevant cardiovascular risk factors in participants found hypertensive is shown in Table 2. The prevalence of reduced estimated glomerular filtration rate (e-GFR) to ⬍60 mL/minute and urine albumin/creatinine ⬎2.5, both indicating kidney disease, was much higher than the self-reported frequency of renal disease, and the frequency of reduced renal function increased with age. Seventy percent (67.01 to 72.79) of the hypertensive participants were aware of the diagnosis and 59% (55.85 to
24.0 (6.01–41.99) 50.6 (39.97–61.15) 48.9 (40.18–57.53) 56.8 (51.47–62.06) 61.7 (54.16–69.29) 65.5 (57.46–73.47) 88.6 (81.45–95.77) 59.0 (55.85–62.07)
6 36 54 147 66 57 54 420
24.0 (6.01–41.99) 40.4 (30.05–50.85) 41.2 (32.68–49.76) 42.9 (37.59–48.12) 40.5 (32.87–48.11) 40.4 (32.23–48.63) 68.4 (57.87–78.84) 43.3 (40.13–46.38)
6 36 54 147 65 57 54 419
100 80.0 ( 67.85–92.15) 84.4 (75.61–93.63) 76.2 (71.40–82.42) 65.0 (55.91––74.79) 62.6 (52.99–73.09) 77.1 (67.94–87.62) 73.6 (70.01–77.27)
21
* Only attendees with relevant home-blood pressure available included.
6 45 64 193 100 91 70 569 48.0 (26.95–69.05) 68.5 (58.70–78.38) 62.6 (54.20–70.99) 68.1 (63.17–73.09) 73.0 (66.12–79.89) 68.8 (61.05–77.51) 93.7 (88.18–99.16) 69.9 (67.01–72.79) 12 61 82 233 119 97 74 678 25 89 131 343 163 141 79 971 20–29 30–39 40–49 50–59 60–69 70–79 80–89 All ages
1.0 (0.63–1.44) 4.6 (3.66–5.53) 10.1 (8.48–11.78) 26.1 (23.76–28.52) 44.9 (39.76–50.04) 56.0 (49.78–62.12) 68.7 (60.09–77.30) 12.6 (11.89–13.37)
% (95% CI) n (95% CI) n % (95% CI) n % (95% CI) % (95% CI) n Age
Prevalence of awareness Prevalence of hypertension
Although arterial hypertension is well recognized as an important factor increasing the risk of cardiovascular disease, the knowledge of its prevalence and the outcome of clinical treatment are sparse and imprecise. There are few nationally representative surveys, and all published studies of prevalence are based on screening BP measured a few times on one occasion.5,6 Such few measurements are for a number of reasons likely to overestimate BP and thereby the prevalence of hypertension and to underestimate the rate of control by treatment.11 In the present study, the number of BP measurements and their reliability were increased by the addition of home measurements in participants with high
n⫽ 7,688*
Discussion
Table 1 Age-specific prevalence, awareness, treatment, and control of hypertension
62.07) were treated with antihypertensive medication (Table 1). By screening BP, 63.1% (59.12 to 67.07) of treated participants were well treated with BP below relevant limits. When BP was estimated by home-BP; however, 73.6% (70.01 to 77.27) were found to be controlled (Table 1). The prevalence of hypertension in the sample corresponds to an age-adjusted prevalence in the adult Danish population of 25.7% (22.98 to 28.41) as estimated by screening BP and 22.3% (19.61 to 24.96) as estimated by home BP. Thus, screening BP overestimated the prevalence by 15.5%. The age-adjusted rate of controlled BP values are 57.4% (47.4 to 67.0) based on screening BP and 68.3% (58.8 to 78.2) based on home-BP (Table 3). A comparison of controlled with not controlled participants showed no difference with respect to classes of antihypertensives employed or the use of combination of two or more classes of drugs (Table 4).The 10-year cumulative cardiovascular risk among participants found hypertensive but not treated was estimated according to the European Society of Hypertension guidelines.10 An added risk of more than 20% was found in 44% of the not treated, and it exceeded 15% in 86% of the untreated hypertensives.
Prevalence of treatment
Figure 2. Crude prevalence of hypertension.
n
Prevalence of control all hypertensives
Prevalence of control treated hypertensives
C.N. Kronberg et al. / Journal of the American Society of Hypertension 3(1) (2009) 19 –24
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Table 2 Prevalence of other risk factors in hypertensive participants as % and (95% Confidence Interval) Risk factors
Prevalence in hypertensive participants
Family history of hypertension (self-reported) Previous cardiovascular disease (self-reported) Diabetes mellitus (self-reported) Fasting p-glucose ⱖ7 mmol/L Renal disease (self-reported) U-albumin/creatinine ⬎2.5 e-GFR ⬍60 mL/minute Total cholesterol ⬎6.5 mmol/L Low-density lipoprotein cholesterol ⬎4.0 mmol/L Smoking
51.8 (48.6–55.1) 12.0 (9.8–14.1) 7.4 (5.7–9.1) 4.2 (2.9–5.4) 2.4 (1.4–3.4) 16.0 (13.7–18.3) 17.3 (13.8–20.7) 6.6 (5.0–8.2) 5.7 (4.2–7.1) 25.4 (22.5–28.2)
e-GFR, estimated glomerular filtration rate. e-GFR is estimated by the Modification of Diet in Renal Disease (MDRD) Study equation.21
screening pressures. This is likely to minimize the “whitecoat effect” of the screening situation and thereby provide values nearer to the usual BP. Thus this procedure solves a part of the methodologic problems in most published prevalence studies. It leaves, however, the possible effect of BP variation and thereby the risk of hypertension by home-BP in persons with normal screening BP because of intraindividual day-to-day variation and so called “masked hypertension.”11–13 This presents a risk of underestimation of prevalence and overestimation of control rate in our study. As with all other prevalence studies published, our survey did not give any information about pretreatment BP in participants classified as hypertensive solely on the basis of self-reported antihypertensive treatment. This involves a risk of white-coat hypertensives erroneously treated being registered as controlled, and thereby an overestimation of this rate.14 Fifteen to 20% of the hypertensive participants who claimed to be on antihypertensive treatment had not redeemed prescriptions on antihypertensive drugs. Eightyfour of those had normal BP, and their labeling as hypertensive relied solely on the self-reported antihypertensive treatment. Thus, the hypertension diagnosis in these cases
may be questionable. Numerically, they account for 8.6% of the subjects classified as being hypertensive. This finding makes the use of self-reported antihypertensive treatment, almost universally used in surveys of hypertension prevalence, uncertain. Selection bias is possible on several levels; our source region may not be representative, and for those invited, attendees may differ from nonattendees. We had unique possibilities to account for such differences. Overall, we found no differences for morbidity directly related to hypertension, use of antihypertensives, or a hypertension diagnosis. Some minor differences were found for socioeconomic status. Because there are not strong associations between socioeconomic variables and hypertension,15 this is unlikely to affect our prevalence estimates materially. The total age-adjusted prevalence of 22.3% is lower than estimated for the world population as a whole,6 but the pattern of increasing prevalence with age is similar. Our findings suggest, with the previously mentioned caveats, that prevalence is overestimated by 15% on the basis of screening BP, and we believe this accounts for the lower prevalence in this study compared with previously published surveys based on a small number of screening BPs. The rates of awareness and treatment in the present study were higher than in most Western countries, but they still leave plenty of room for improvement. Thus one-third of hypertensives was not aware of the diagnosis and just below one-half was not treated, although the majority of them had a significantly increased cardiovascular risk based on BP and other risk factors. Also, the rate of controlled BP in the hypertensive population as a whole is disappointingly low. The most remarkable result of the present survey is the high rate of BP control in treated participants. The control of 63% as estimated by screening BP and 74% by home-BP is fully comparable with the results of controlled clinical trials. The lack of difference between controlled and uncontrolled hypertensive patients with regard to pharmacologic treatment suggests insufficient use of combination therapy to be an unlikely explanation of insufficient control in the present series. By age adjustment, 43.4% of hypertensives in Denmark were found to be controlled. This figure is higher than those reported from other European countries,16 mostly estimated a decade ago. A few recent surveys have, however, found
Table 3 Unadjusted and age-adjusted prevalence (%) based on screening and home blood pressures Screening blood pressure
Hypertension Awareness Treatment Control of treated
Home blood pressure
Unadjusted
Age-adjusted
Unadjusted
Age-adjusted
15.2 (14.4–16.0) 60.9 (58.1–63.7) 48.5 (45.7–51.4) 63.1 (59.1–67.1)
25.7 (22.7–28.4) 63.5 (57.3–76.1) 53.3 (46.1–60.3) 57.4 (47.4–67.1)
12.6 (11.9–13.4) 69.9 (67.0–72.8) 59.0 (55.9–62.1) 72.1 (68.3–76.0)
22.3 (19.4–25.0) 72.7 (65.8–79.5) 63.5 (58.9–70.8) 68.3 (58.8–78.2)
C.N. Kronberg et al. / Journal of the American Society of Hypertension 3(1) (2009) 19 –24 Table 4 Comparison of antihypertensive therapy in participants with controlled and not controlled hypertension; uncontrolled patients were assessed by both ambulatory and home measurements Treatment
Controlled (n ⫽ 420)
Uncontrolled (n ⫽ 149)
P value
Thiazides -blockers Calcium channel blockers Angiotensin-converting enzyme inhibitors Angiotensin receptor antagonists No antihypertensive recorded One antihypertensive Two antihypertensives Three antihypertensives Four or more antihypertensives
166 (39.5%) 99 (23.6%) 104 (24.8%)
50 (33.6%) 38 (25.5%) 45 (30.2%)
NS NS NS
106 (25.2%)
39 (26.2%)
NS
108 (25.7%)
38 (25.5%)
NS
84 (20.0%)
23 (15.4%)
NS
156 (37.1%) 126 (30.0%) 42 (10.0%) 12 (2.9%)
63 (42.3%) 46 (30.9%) 13 (8.7%) 4 (2.7%)
NS NS NS NS
NS, not significant: P ⬎ .05.
control rates similar to those reported here. A survey of a large population sample in Cuba found a similar prevalence of hypertension. Also, awareness and the rate of treatment were almost identical, and 62% of those treated were controlled with a BP lower than 140/90 mm Hg measured in the screening clinic.17 As in our study, an analysis of the Spanish Ambulatory Blood Pressure Monitoring Registry showed a higher rate of BP control when estimated with out of office measurements; in this case, 52% by average daytime values of ambulatory BP monitoring.18 A recent analysis of data from the National Health and Nutrition Examination Survey in the United States19 showed an age-adjusted prevalence of 29.6%. Those with hypertension 65.1% were being treated and 63.9% of the treated were controlled. These figures are very similar to our comparable findings based on screening BP. A previous Danish study based on screening BPs found a prevalence of 38.5%, with less than 40% aware and half of those aware of the diagnosis untreated. Only 21% of treated hypertensives were controlled, corresponding to a mere 4% of all hypertensives.8 These figures are considerably lower than those of the present study. We suggest that hypertension control in Denmark has improved considerably between 1998 and 2004, the times of the two studies.
Conclusion The rate of controlled BP by antihypertensive treatment in the present population based study of clinical practice is comparable with the best reported from community surveys16 and clinical trials.20 In our opinion, the Danish Health Care system, which is easily accessible, financed by
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taxation and thus free of other cost to all citizens, is part of an explanation for the favorable results of antihypertensive treatment. Our data, however, still demonstrate insufficient detection of arterial hypertension and initiation of treatment, and point to the importance of further implementation of current guidelines. The success of the Canadian Hypertension Education Program,22 with a recently reported 69% control rate,23 sets a good example for such endeavors.
References 1. Ezzati M, Lopez AD, Rodgers A, van der Horn S, Murray CJL. Selected major risk factors and global and regional burden of disease. Lancet 2002;360:1347– 60. 2. WHO. World health report 2002; reducing risk, promoting healthy life. Geneva, Switzerland. World Health Organization, 2002. 3. Blood Pressure Lowering Treatment Trialists’ Collaboration. Effect of different blood-pressure-lowering regimens on major cardiovascular events: results of prospectively-designed overviews of randomised trails. Lancet 2003;362:1527–35. 4. Mancia G, Grassi G. Systolic and diastolic blood pressure control in antihypertensive drug trials. J Hypertens 2002;20:1461– 4. 5. Kearney PM, Whelton M, Reynolds K, Muntner P, Whelton P, He Jiang. Worldwide prevalence of hypertension: a systematic review. J Hypertens 2004; 22:11–9. 6. Kearney PM, Whelton M, Reynolds K, Muntner P, Whelton P, He J. Global burden of hypertension: analysis of worldwide data. Lancet 2005;365:217–23. 7. Burt VL, Cutler AJ, Higgins M, Horan MJ, Labarthe D, Whelton P, et al. Trends in the prevalence, awareness, treatment and control of hypertension in the US adult population. Hypertension 1995;26:60 –9 8. Sehested T, Ibsen H, Jøgensen T. Awareness, treatment and control of hypertension in Denmark. The Inter99 study. Blood Press 2007;16:312–19. 9. Rogoza AN, Pavlova TS, Sergeeva MV. Validation of A&D UA-676 device for self-measurement of blood pressure. Blood Press Monitor 2000;5:227–31. 10. 2003 European Society of Hypertension-European Society of Cardiology guide lines for the management of arterial hypertension. J Hypertens 2003;21:1011–53. 11. Klungel OH, de Boer A, Paes AHP, Nagelkerke NJD, Seidell JC, Bakker A. Estimating the prevalence of hypertension corrected for the effect of within-person variability in blood pressure. J Clin Epidemiol 2000;53: 1158 – 63. 12. Longo D, Dorigatti F. Palatini P. Masked hypertension in adults. Blood Press Monitor 2005;10:307–10.
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13. Pickering TG, Davidson K, Gerin W, Schwartz JE. Masked hypertension. Hypertension 2002;40:795–96. 14. Mancia G. Effective ambulatory blood pressure control in medical practice. Hypertension 2007;49:17– 8. 15. Kaplan GA, Keil JE. Socioeconomic factors and cardiovascular disease: a review of the literature. Circulation 1993;88:1973–98. 16. Erdine S. Eur Soc Hypertens Scient Newsl 2007. www.eshonline.org/education/newsletter/2007_03.pdf. 17. Orduñez-Garcia P, Bernal Munoz JL, Pedraza D, Espinosa-Brito A, Silva LC, Cooper RS. Success in control of hypertension in a low-resource setting: the Cuban experience. J Hypertens 2006;24:845– 49. 18. Banegas JR, Segura J, Sobrino J, Rodríguez-Artalejo F, de la Sierra A, de la Cruz JJ, et al. Effectiveness of blood pressure control outside the medical setting. Hypertension 2007;49:62– 8. 19. Ong KL, Cheung BMY, Man YB, Lau CP, Lam KSL. Prevalence, awareness, treatment, and control of hypertension among Unites States adults 1999 – 2004. Hypertension 2007;49:69 –75.
20. The ALLHAT Officers and Coordinators for the ALLHAT Collaborative Research Group. Major outcomes in high-risk hypertensive patients randomized to angiotensin-converting enzyme inhibitor or calcium channel inhibitor vs. diuretic. The Antihypertensive and LipidLowering Treatment to Prevent Heart Attack Trial (ALLHAT). JAMA 2002;288:2981–97. 21. Levey SA, Coresh J, Greene T, Stevens LA, Zhang Y, Hendriksen S, et al. Using standardized serum creatinine values in the modification of diet in renal disease study. Equation for estimating glomerular filtration rate. Ann Intern Med 2006;145:247–54. 22. Onysko J, Maxwell C, Eliaziw M, Zhang JX, Johansen H, Campbell NRC. Large increases in hypertension diagnosis and treatment in Canada after a healthcare professional education program. Hypertension 2006;48:853– 60. 23. Drouin D, Kaczorowski J, Campbell NR, Lewanczuk RR. Implementing guidelines. It is working in Canada. ESH/ISH Scientific Meeting, Berlin, Germany 2008. Abstract OS 14/1.
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Supplemental Text Prevalence of Hypertension in Denmark To ascertain a possible selection bias in the attendance of the survey, data on use of certain cardiovascular drugs and of cardiovascular diagnoses from previous inpatient contacts of attendees and nonattendees were compared. Data sources were the Odense University Pharmacoepidemiological Database1 and the Funen County patient administrative system. For all drugs, the subject was classified as user on the day of invitation, if he had redeemed at least one prescription on the drug within the past 120 days. Relevant diagnoses were registered on the basis of previous admissions or outpatient contacts. Data on socioeconomic status of attendees and nonattendees were obtained from Statistics Denmark (www.dst.dk). To adjust for differences in age and gender between attendees and nonattendees, the standardized prevalence ratio of use for each drug was calculated. An indirect standardization procedure using the attendees as reference was employed (ie, for the attendees the ratio between the observed number of users and the expected number was calculated, had they had the same age- and gender-specific prevalences as the nonattendees). A similar technique was used for the disease prevalences and for socioeconomic status. Age was categorized in 10-year bands. Confidence intervals for the standardized prevalence ratios were calculated by the method suggested by Morris and Gardner.2 To account for a possible nonrepresentativeness in our source population, we retrieved data on physician contacts, cardiovascular morbidity, and socioeconomic status in the four participating municipalities in our study and in Den-
24.e1
mark as a whole. Age-standardized prevalence ratios were calculated by the same method as described for the attendee vs. nonattendee analysis. The data source was Statistics Denmark. The comparison of socioeconomic status of the source population with the Danish population as a whole showed slightly more unemployed, early retired, and cash benefit recipients in the region studied (Supplemental Table 1). Likewise, there were fewer hospital admissions and fewer cases of ischemic heart disease and stroke in the population used as a basis for the study sample. The differences were, however, modest (Supplemental Table 2). Fifty percent of the invited population sample attended the survey. Comparison of attendees and nonattendees on the basis of previous hypertension related diagnoses, current medication, and socioeconomic variables showed slightly fewer diabetics in the group of attendees (Supplemental Table 3). Fewer cash benefit recipients and early retired accepted the invitation and employed did so slightly more often than not (Supplemental Table 4).
References 1. Gaist D, Sørensen HT, Hallas J. The Danish prescription registers. Dan Med Bull 1997;44:445– 48. 2. Morris JA, Gardner MJ. Calculating confidence intervals for relative risk, odds ratios and standardised ratios and rates. In: Gardner MJ, Altman DG, Statistics with confidence. London, England: British Medical Journal Publishing, 1989:60 –1.
Supplemental Table 1 The basis for the study population compared to the national population by socioeconomic parameters (%)
Urban residents Self-employed Employed Unemployed Early retired Cash benefit recipients
Denmark
Basis of population sample
Age-adjusted ratio
85 4.68 47.43 2.94 5.91 2.81
85 3.45 46.1 3.40 6.87 3.77
0.74 (0.73–0.76) 0.97 (0.97–0.98) 1.16 (1.14–1.18) 1.17 (1.15–1.18) 1.35 (1.32–1.37)
Supplemental Table 2 The basis for the study population compared to the national population by health related frequencies (events or registered diagnosis/100 persons/year)
Contacts to general practice Hospital admissions Hypertension Ischemic heart disease Stroke Diabetes
Denmark
Basis of population sample
Age-adjusted ratio
168.87 23.58 0.13 1.06 0.48 0.20
168.28 19.72 0.12 0.75 0.37 0.18
1.00 (0.99–1.00) 0.89 (0.88–0.90) 0.96 (0.82–1.11) 0.75 (0.71–0.80) 0.82 (0.75–0.88) 0.97 (0.86–1.09)
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C.N. Kronberg et al. / Journal of the American Society of Hypertension 3(1) (2009) 19 –24
Supplemental Table 3 Comparison of nonattendees and attendees by current use of hypertension related medication and diagnosis of hypertension related disease Characteristic Current use of Thiazides -blockers Calcium channel blockers Angiotensin-converting enzyme inhibitors or A2RA Any of the above Antidiabetics Low-dose aspirin Statins Any past diagnosis of Hypertension Diabetes Ischemic heart disease Cerebrovascular disease
Nonattendees (n ⫽ 7,866)
Attendees (n ⫽ 7,770)
Standardized prevalence ratio (CI)
242 (3.1%) 208 (2.6%) 188 (2.4%) 185 (2.4%)
268 (3.4%) 205 (2.6%) 173 (2.2%) 175 (2.3%)
1.07 (0.89–1.28) 0.92 (0.75–1.12) 0.98 (0.79–1.21) 0.85 (0.69–1.05)
602 (7.7%) 145 (1.8%) 129 (1.6%) 126 (1.6%)
611 (7.9%) 92 (1.2%) 110 (1.4%) 151 (1.9%)
0.96 (0.86–1.08) 0.60 (0.46–0.79) 1.00 (0.77–1.30) 0.94 (0.73–1.20)
202 (2.6%) 161 (2.0%) 160 (2.0%) 115 (1.5%)
191 (2.5%) 115 (1.5%) 157 (2.0%) 82 (1.1%)
0.91 (0.74–1.11) 0.66 (0.51–0.84) 1.04 (0.83–1.30) 0.78 (0.58–1.05)
CI, confidence interval. Supplemental Table 4 Comparison of nonattendees and attendees by socioeconomic factors for the 14,917 persons for whom data were available
Pensioners and others Unemployed Early retired Cash benefit recipients Employed Self-employed
Nonattendees (n ⫽ 7,341)
Attendees (n ⫽ 7,576)
Standardized prevalence ratio (95% confidence interval)
2530 (34% ) 238 (3% ) 422 (5% ) 273 (3% ) 3699 (50%) 179 (2%)
2266 (29%) 245 (3%) 280 (3%) 116 (1%) 4475 (59%) 194 (2%)
0.87 (0.84–0.89) 1.00 (0.91–1.09) 0.64 (0.59–0.70) 0.41 (0.36–0.47) 1.17 (1.15–1.20) 1.05 (0.95–1.16)
Research Article
Prevalence, awareness, and control of arterial hypertension in Denmark Christel N. Kronborg, MD, PhD, Jesper Hallas, MD, DMSc, and Ib A. Jacobsen, MD, DMSc* Department of Internal Medicine C, Odense University Hospital, Odense, Denmark Manuscript received May 12, 2008 and accepted August 1, 2008
Abstract Hypertension is an important modifiable risk factor for cardiovascular disease. Risk is reduced by reduction of blood pressure (BP). The present survey estimated the prevalence of hypertension, awareness, treatment, and BP control in Denmark. BP was measured three times on one occasion in a representative sample (n ⫽ 7,767) of the Danish population ages 20 to 89 years. Persons with screening BP ⱖ140/90 mm Hg also measured BP at home. Participants with home BP ⱖ135/85 mm Hg in general and ⱖ125/75 mm Hg for patients with diabetes or renal disease were categorized as hypertensive together with those already on antihypertensive treatment. Awareness was registered by questionnaire. Treated patients with BP below relevant limits were categorized as controlled. Age-adjusted prevalence of hypertension was on the basis of screening BP 25.7% and by home BP 22.3%. Seventy-two percent of patients found hypertensive by home BP were aware of it, 64% were treated, and 57% of those treated were controlled by office BP and 68% by home BP. One-fifth of the adult Danish population was found to be hypertensive, Awareness and control of hypertension was better than in most previous reports. Control rates similar to those of clinical trials are achievable in clinical practice. J Am Soc Hypertens 2009;3(1): 19 –24. © 2009 American Society of Hypertension. All rights reserved. Keywords: Epidemiology; antihypertensive therapy; detection; blood pressure.
Introduction High blood pressure (BP) is an important risk to health in all parts of the world. It increases the risk of cardiovascular disease; thus, about two-thirds of cerebrovascular disease and half of ischemic heart disease is attributable to arterial hypertension.1,2 There is ample evidence that the cardiovascular risk in hypertensive patients is reduced significantly by lowering BP, most effectively with the aid of antihypertensive drugs.3 Normalization of BP is not easily achieved, even in controlled trials with optimal motivation both for patients and for treating physicians. The recommended goal of a diaThis study was funded by Apotekerfonden of 1991, The Danish Heart Foundation, The University of Southern Denmark, the County of Funen, and to a smaller extent by Pfizer, Novartis, Boehringer-Ingelheim, Solvay, and Sanofi-Synthelabo. Dr. Hallas has received research Grants from Novartis, Nycomed, and Merck Sharp & Dohme, and fees for teaching from Astra-Zeneca, Nycomed, Pfizer, and the Danish Association of Pharmaceutical Industry. Supplemental Material is available at www.ashjournal.com. *Corresponding author: Ib A. Jacobsen, MD, DMSc, Department of Endocrinology M, Odense University Hospital, DK-5000 Odense, Denmark. Tel: ⫹45 2720313; fax: ⫹45 65919653. E-mail: [email protected]
stolic BP lower than 90 mm Hg is frequently achieved, whereas a systolic BP lower than 140 mm Hg presents a greater problem. The lower goals for hypertensive patients with diabetes and nephropathy are infrequently reached.4 Surveys of antihypertensive treatment in clinical practice have shown even less favorable results.5 A recent analysis estimated that more than one-fourth of the world’s adult population is hypertensive, with considerable variation in prevalence between regions.6 In economically developed countries, only half to two-thirds of the hypertensive population were aware of the diagnosis, fewer than half of them were treated, and less than one-third of hypertensives had their BP controlled by treatment. In economically developing counties, the results are even more dismal.5 The task of today’s health services is to transfer available knowledge of effective antihypertensive treatment from controlled trials to clinical practice. The present survey is a study of the prevalence, awareness, treatment, and control of hypertension in Denmark.
Methods The study was designed as a representative cross-sectional survey of the Danish population. For practical reasons, it was based on a population sample randomly drawn
1933-1711/09/$ – see front matter © 2009 American Society of Hypertension. All rights reserved. doi:10.1016/j.jash.2008.08.001
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Informed Consent All participants have given written consent after oral and written information. The study was approved by the regional ethics committee for Funen and Vejle Counties (VF 20020213) and by the Danish data protection agency.
Statistics
Figure 1. Total number of subjects in the survey.
from a geographic area comprising the city of Odense (the home of The University of Southern Denmark) and three surrounding rural municipalities. The necessary sample size was calculated on the basis of expected prevalence based on data from the National Health and Nutrition Examination Survey III and Inter-99 surveys,7,8 and stratified according to age and gender. A sample of 15,633 persons (Figure 1) stratified in 10year bands, comprising the age range 20 to 89 years and both genders, was randomly drawn from the Central persons register, which contains data on all Danish citizens. The population sample was invited to the hypertension clinic for BP screening. BP was measured in the sitting position by a trained nurse after 5 minutes’ rest and with a standard mercury sphygmomanometer. Initial measurements were performed on both arms, and a further three measurements were performed on the arm with the highest pressure. The mean of the two latest measurements was used as screening BP. Participants with elevated screening BP were asked to measure their BP at home, three times in the morning and three times in the evening for three consecutive days using a validated device after instruction by a trained nurse (A&D UA767; A&D Company Ltd, Tokyo, Japan).9 The mean of home-BP measured on the last two days was used as the home-BP for further analysis. Participants with elevated home-BP and those on current antihypertensive treatment were registered as hypertensives. Screening-BP ⱖ140/90 mm Hg was registered as elevated in general and in cases of diabetes mellitus or nephropathy, participants with BP ⱖ130/80 mm Hg were registered as hypertensives. The corresponding home-BP were ⱖ135/85 mm Hg and ⱖ125/75 mm Hg. Treated participants with home-BP below the relevant limits were registered as controlled. All participants were asked to fill in a questionnaire at the screening center about relevant medical history, other cardiovascular risk factors, and current medication. Participants diagnosed with hypertension had blood and urine samples collected for serum electrolytes, serum creatinine, serum lipids, plasma glucose, and urine albumin excretion.
To ascertain a possible selection bias in the attendance of the survey, data on use of certain cardiovascular drugs and of cardiovascular diagnoses from previous inpatient contacts of attendees and nonattendees were compared (see Supplemental text available at Ashjournal.com). To account for a possible nonrepresentativeness in our source population, we retrieved data on physician contacts, cardiovascular morbidity, and socioeconomic status in the four participating municipalities in our study and in Denmark as a whole (see Supplemental text). Statistical analysis was performed with SPSS version 13.0 for Windows (SPSS Inc, Chicago, IL). Prevalence is reported with 95% confidence intervals. Age-adjusted prevalences were calculated on the basis of the Danish population in 2006.
Results The comparison of socioeconomic status and health-related characteristics of the source population with the Danish population as a whole showed only minor differences (see Supplemental Tables 1 and 2 available at Ashjournal. com). Fifty percent of the invited population sample attended the survey. Comparison of attendees and nonattendees on the basis of previous hypertension-related diagnoses, current medication, and socioeconomic variables showed the two groups to be comparable (see Supplemental Tables 3 and 4). Thus, the examined population sample was found to be representative of the general Danish population. Based on screening-BP, 1104 or 14.4% (13.6 to 15.1) of the participants were hypertensive, whereas 971 or 12.6% (11.9 to 13.4) were hypertensive on the basis of home-BP. The age-specific prevalence of hypertension based on home-BP varied markedly from 1% in the 20- to 29-year-old group to 69% in the 80- to 89-year-old group (Figure 2; Table 1). There was no significant difference between the prevalence in men and women, and all results are accordingly presented by age alone. The frequency of other relevant cardiovascular risk factors in participants found hypertensive is shown in Table 2. The prevalence of reduced estimated glomerular filtration rate (e-GFR) to ⬍60 mL/minute and urine albumin/creatinine ⬎2.5, both indicating kidney disease, was much higher than the self-reported frequency of renal disease, and the frequency of reduced renal function increased with age. Seventy percent (67.01 to 72.79) of the hypertensive participants were aware of the diagnosis and 59% (55.85 to
24.0 (6.01–41.99) 50.6 (39.97–61.15) 48.9 (40.18–57.53) 56.8 (51.47–62.06) 61.7 (54.16–69.29) 65.5 (57.46–73.47) 88.6 (81.45–95.77) 59.0 (55.85–62.07)
6 36 54 147 66 57 54 420
24.0 (6.01–41.99) 40.4 (30.05–50.85) 41.2 (32.68–49.76) 42.9 (37.59–48.12) 40.5 (32.87–48.11) 40.4 (32.23–48.63) 68.4 (57.87–78.84) 43.3 (40.13–46.38)
6 36 54 147 65 57 54 419
100 80.0 ( 67.85–92.15) 84.4 (75.61–93.63) 76.2 (71.40–82.42) 65.0 (55.91––74.79) 62.6 (52.99–73.09) 77.1 (67.94–87.62) 73.6 (70.01–77.27)
21
* Only attendees with relevant home-blood pressure available included.
6 45 64 193 100 91 70 569 48.0 (26.95–69.05) 68.5 (58.70–78.38) 62.6 (54.20–70.99) 68.1 (63.17–73.09) 73.0 (66.12–79.89) 68.8 (61.05–77.51) 93.7 (88.18–99.16) 69.9 (67.01–72.79) 12 61 82 233 119 97 74 678 25 89 131 343 163 141 79 971 20–29 30–39 40–49 50–59 60–69 70–79 80–89 All ages
1.0 (0.63–1.44) 4.6 (3.66–5.53) 10.1 (8.48–11.78) 26.1 (23.76–28.52) 44.9 (39.76–50.04) 56.0 (49.78–62.12) 68.7 (60.09–77.30) 12.6 (11.89–13.37)
% (95% CI) n (95% CI) n % (95% CI) n % (95% CI) % (95% CI) n Age
Prevalence of awareness Prevalence of hypertension
Although arterial hypertension is well recognized as an important factor increasing the risk of cardiovascular disease, the knowledge of its prevalence and the outcome of clinical treatment are sparse and imprecise. There are few nationally representative surveys, and all published studies of prevalence are based on screening BP measured a few times on one occasion.5,6 Such few measurements are for a number of reasons likely to overestimate BP and thereby the prevalence of hypertension and to underestimate the rate of control by treatment.11 In the present study, the number of BP measurements and their reliability were increased by the addition of home measurements in participants with high
n⫽ 7,688*
Discussion
Table 1 Age-specific prevalence, awareness, treatment, and control of hypertension
62.07) were treated with antihypertensive medication (Table 1). By screening BP, 63.1% (59.12 to 67.07) of treated participants were well treated with BP below relevant limits. When BP was estimated by home-BP; however, 73.6% (70.01 to 77.27) were found to be controlled (Table 1). The prevalence of hypertension in the sample corresponds to an age-adjusted prevalence in the adult Danish population of 25.7% (22.98 to 28.41) as estimated by screening BP and 22.3% (19.61 to 24.96) as estimated by home BP. Thus, screening BP overestimated the prevalence by 15.5%. The age-adjusted rate of controlled BP values are 57.4% (47.4 to 67.0) based on screening BP and 68.3% (58.8 to 78.2) based on home-BP (Table 3). A comparison of controlled with not controlled participants showed no difference with respect to classes of antihypertensives employed or the use of combination of two or more classes of drugs (Table 4).The 10-year cumulative cardiovascular risk among participants found hypertensive but not treated was estimated according to the European Society of Hypertension guidelines.10 An added risk of more than 20% was found in 44% of the not treated, and it exceeded 15% in 86% of the untreated hypertensives.
Prevalence of treatment
Figure 2. Crude prevalence of hypertension.
n
Prevalence of control all hypertensives
Prevalence of control treated hypertensives
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Table 2 Prevalence of other risk factors in hypertensive participants as % and (95% Confidence Interval) Risk factors
Prevalence in hypertensive participants
Family history of hypertension (self-reported) Previous cardiovascular disease (self-reported) Diabetes mellitus (self-reported) Fasting p-glucose ⱖ7 mmol/L Renal disease (self-reported) U-albumin/creatinine ⬎2.5 e-GFR ⬍60 mL/minute Total cholesterol ⬎6.5 mmol/L Low-density lipoprotein cholesterol ⬎4.0 mmol/L Smoking
51.8 (48.6–55.1) 12.0 (9.8–14.1) 7.4 (5.7–9.1) 4.2 (2.9–5.4) 2.4 (1.4–3.4) 16.0 (13.7–18.3) 17.3 (13.8–20.7) 6.6 (5.0–8.2) 5.7 (4.2–7.1) 25.4 (22.5–28.2)
e-GFR, estimated glomerular filtration rate. e-GFR is estimated by the Modification of Diet in Renal Disease (MDRD) Study equation.21
screening pressures. This is likely to minimize the “whitecoat effect” of the screening situation and thereby provide values nearer to the usual BP. Thus this procedure solves a part of the methodologic problems in most published prevalence studies. It leaves, however, the possible effect of BP variation and thereby the risk of hypertension by home-BP in persons with normal screening BP because of intraindividual day-to-day variation and so called “masked hypertension.”11–13 This presents a risk of underestimation of prevalence and overestimation of control rate in our study. As with all other prevalence studies published, our survey did not give any information about pretreatment BP in participants classified as hypertensive solely on the basis of self-reported antihypertensive treatment. This involves a risk of white-coat hypertensives erroneously treated being registered as controlled, and thereby an overestimation of this rate.14 Fifteen to 20% of the hypertensive participants who claimed to be on antihypertensive treatment had not redeemed prescriptions on antihypertensive drugs. Eightyfour of those had normal BP, and their labeling as hypertensive relied solely on the self-reported antihypertensive treatment. Thus, the hypertension diagnosis in these cases
may be questionable. Numerically, they account for 8.6% of the subjects classified as being hypertensive. This finding makes the use of self-reported antihypertensive treatment, almost universally used in surveys of hypertension prevalence, uncertain. Selection bias is possible on several levels; our source region may not be representative, and for those invited, attendees may differ from nonattendees. We had unique possibilities to account for such differences. Overall, we found no differences for morbidity directly related to hypertension, use of antihypertensives, or a hypertension diagnosis. Some minor differences were found for socioeconomic status. Because there are not strong associations between socioeconomic variables and hypertension,15 this is unlikely to affect our prevalence estimates materially. The total age-adjusted prevalence of 22.3% is lower than estimated for the world population as a whole,6 but the pattern of increasing prevalence with age is similar. Our findings suggest, with the previously mentioned caveats, that prevalence is overestimated by 15% on the basis of screening BP, and we believe this accounts for the lower prevalence in this study compared with previously published surveys based on a small number of screening BPs. The rates of awareness and treatment in the present study were higher than in most Western countries, but they still leave plenty of room for improvement. Thus one-third of hypertensives was not aware of the diagnosis and just below one-half was not treated, although the majority of them had a significantly increased cardiovascular risk based on BP and other risk factors. Also, the rate of controlled BP in the hypertensive population as a whole is disappointingly low. The most remarkable result of the present survey is the high rate of BP control in treated participants. The control of 63% as estimated by screening BP and 74% by home-BP is fully comparable with the results of controlled clinical trials. The lack of difference between controlled and uncontrolled hypertensive patients with regard to pharmacologic treatment suggests insufficient use of combination therapy to be an unlikely explanation of insufficient control in the present series. By age adjustment, 43.4% of hypertensives in Denmark were found to be controlled. This figure is higher than those reported from other European countries,16 mostly estimated a decade ago. A few recent surveys have, however, found
Table 3 Unadjusted and age-adjusted prevalence (%) based on screening and home blood pressures Screening blood pressure
Hypertension Awareness Treatment Control of treated
Home blood pressure
Unadjusted
Age-adjusted
Unadjusted
Age-adjusted
15.2 (14.4–16.0) 60.9 (58.1–63.7) 48.5 (45.7–51.4) 63.1 (59.1–67.1)
25.7 (22.7–28.4) 63.5 (57.3–76.1) 53.3 (46.1–60.3) 57.4 (47.4–67.1)
12.6 (11.9–13.4) 69.9 (67.0–72.8) 59.0 (55.9–62.1) 72.1 (68.3–76.0)
22.3 (19.4–25.0) 72.7 (65.8–79.5) 63.5 (58.9–70.8) 68.3 (58.8–78.2)
C.N. Kronberg et al. / Journal of the American Society of Hypertension 3(1) (2009) 19 –24 Table 4 Comparison of antihypertensive therapy in participants with controlled and not controlled hypertension; uncontrolled patients were assessed by both ambulatory and home measurements Treatment
Controlled (n ⫽ 420)
Uncontrolled (n ⫽ 149)
P value
Thiazides -blockers Calcium channel blockers Angiotensin-converting enzyme inhibitors Angiotensin receptor antagonists No antihypertensive recorded One antihypertensive Two antihypertensives Three antihypertensives Four or more antihypertensives
166 (39.5%) 99 (23.6%) 104 (24.8%)
50 (33.6%) 38 (25.5%) 45 (30.2%)
NS NS NS
106 (25.2%)
39 (26.2%)
NS
108 (25.7%)
38 (25.5%)
NS
84 (20.0%)
23 (15.4%)
NS
156 (37.1%) 126 (30.0%) 42 (10.0%) 12 (2.9%)
63 (42.3%) 46 (30.9%) 13 (8.7%) 4 (2.7%)
NS NS NS NS
NS, not significant: P ⬎ .05.
control rates similar to those reported here. A survey of a large population sample in Cuba found a similar prevalence of hypertension. Also, awareness and the rate of treatment were almost identical, and 62% of those treated were controlled with a BP lower than 140/90 mm Hg measured in the screening clinic.17 As in our study, an analysis of the Spanish Ambulatory Blood Pressure Monitoring Registry showed a higher rate of BP control when estimated with out of office measurements; in this case, 52% by average daytime values of ambulatory BP monitoring.18 A recent analysis of data from the National Health and Nutrition Examination Survey in the United States19 showed an age-adjusted prevalence of 29.6%. Those with hypertension 65.1% were being treated and 63.9% of the treated were controlled. These figures are very similar to our comparable findings based on screening BP. A previous Danish study based on screening BPs found a prevalence of 38.5%, with less than 40% aware and half of those aware of the diagnosis untreated. Only 21% of treated hypertensives were controlled, corresponding to a mere 4% of all hypertensives.8 These figures are considerably lower than those of the present study. We suggest that hypertension control in Denmark has improved considerably between 1998 and 2004, the times of the two studies.
Conclusion The rate of controlled BP by antihypertensive treatment in the present population based study of clinical practice is comparable with the best reported from community surveys16 and clinical trials.20 In our opinion, the Danish Health Care system, which is easily accessible, financed by
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taxation and thus free of other cost to all citizens, is part of an explanation for the favorable results of antihypertensive treatment. Our data, however, still demonstrate insufficient detection of arterial hypertension and initiation of treatment, and point to the importance of further implementation of current guidelines. The success of the Canadian Hypertension Education Program,22 with a recently reported 69% control rate,23 sets a good example for such endeavors.
References 1. Ezzati M, Lopez AD, Rodgers A, van der Horn S, Murray CJL. Selected major risk factors and global and regional burden of disease. Lancet 2002;360:1347– 60. 2. WHO. World health report 2002; reducing risk, promoting healthy life. Geneva, Switzerland. World Health Organization, 2002. 3. Blood Pressure Lowering Treatment Trialists’ Collaboration. Effect of different blood-pressure-lowering regimens on major cardiovascular events: results of prospectively-designed overviews of randomised trails. Lancet 2003;362:1527–35. 4. Mancia G, Grassi G. Systolic and diastolic blood pressure control in antihypertensive drug trials. J Hypertens 2002;20:1461– 4. 5. Kearney PM, Whelton M, Reynolds K, Muntner P, Whelton P, He Jiang. Worldwide prevalence of hypertension: a systematic review. J Hypertens 2004; 22:11–9. 6. Kearney PM, Whelton M, Reynolds K, Muntner P, Whelton P, He J. Global burden of hypertension: analysis of worldwide data. Lancet 2005;365:217–23. 7. Burt VL, Cutler AJ, Higgins M, Horan MJ, Labarthe D, Whelton P, et al. Trends in the prevalence, awareness, treatment and control of hypertension in the US adult population. Hypertension 1995;26:60 –9 8. Sehested T, Ibsen H, Jøgensen T. Awareness, treatment and control of hypertension in Denmark. The Inter99 study. Blood Press 2007;16:312–19. 9. Rogoza AN, Pavlova TS, Sergeeva MV. Validation of A&D UA-676 device for self-measurement of blood pressure. Blood Press Monitor 2000;5:227–31. 10. 2003 European Society of Hypertension-European Society of Cardiology guide lines for the management of arterial hypertension. J Hypertens 2003;21:1011–53. 11. Klungel OH, de Boer A, Paes AHP, Nagelkerke NJD, Seidell JC, Bakker A. Estimating the prevalence of hypertension corrected for the effect of within-person variability in blood pressure. J Clin Epidemiol 2000;53: 1158 – 63. 12. Longo D, Dorigatti F. Palatini P. Masked hypertension in adults. Blood Press Monitor 2005;10:307–10.
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13. Pickering TG, Davidson K, Gerin W, Schwartz JE. Masked hypertension. Hypertension 2002;40:795–96. 14. Mancia G. Effective ambulatory blood pressure control in medical practice. Hypertension 2007;49:17– 8. 15. Kaplan GA, Keil JE. Socioeconomic factors and cardiovascular disease: a review of the literature. Circulation 1993;88:1973–98. 16. Erdine S. Eur Soc Hypertens Scient Newsl 2007. www.eshonline.org/education/newsletter/2007_03.pdf. 17. Orduñez-Garcia P, Bernal Munoz JL, Pedraza D, Espinosa-Brito A, Silva LC, Cooper RS. Success in control of hypertension in a low-resource setting: the Cuban experience. J Hypertens 2006;24:845– 49. 18. Banegas JR, Segura J, Sobrino J, Rodríguez-Artalejo F, de la Sierra A, de la Cruz JJ, et al. Effectiveness of blood pressure control outside the medical setting. Hypertension 2007;49:62– 8. 19. Ong KL, Cheung BMY, Man YB, Lau CP, Lam KSL. Prevalence, awareness, treatment, and control of hypertension among Unites States adults 1999 – 2004. Hypertension 2007;49:69 –75.
20. The ALLHAT Officers and Coordinators for the ALLHAT Collaborative Research Group. Major outcomes in high-risk hypertensive patients randomized to angiotensin-converting enzyme inhibitor or calcium channel inhibitor vs. diuretic. The Antihypertensive and LipidLowering Treatment to Prevent Heart Attack Trial (ALLHAT). JAMA 2002;288:2981–97. 21. Levey SA, Coresh J, Greene T, Stevens LA, Zhang Y, Hendriksen S, et al. Using standardized serum creatinine values in the modification of diet in renal disease study. Equation for estimating glomerular filtration rate. Ann Intern Med 2006;145:247–54. 22. Onysko J, Maxwell C, Eliaziw M, Zhang JX, Johansen H, Campbell NRC. Large increases in hypertension diagnosis and treatment in Canada after a healthcare professional education program. Hypertension 2006;48:853– 60. 23. Drouin D, Kaczorowski J, Campbell NR, Lewanczuk RR. Implementing guidelines. It is working in Canada. ESH/ISH Scientific Meeting, Berlin, Germany 2008. Abstract OS 14/1.
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Supplemental Text Prevalence of Hypertension in Denmark To ascertain a possible selection bias in the attendance of the survey, data on use of certain cardiovascular drugs and of cardiovascular diagnoses from previous inpatient contacts of attendees and nonattendees were compared. Data sources were the Odense University Pharmacoepidemiological Database1 and the Funen County patient administrative system. For all drugs, the subject was classified as user on the day of invitation, if he had redeemed at least one prescription on the drug within the past 120 days. Relevant diagnoses were registered on the basis of previous admissions or outpatient contacts. Data on socioeconomic status of attendees and nonattendees were obtained from Statistics Denmark (www.dst.dk). To adjust for differences in age and gender between attendees and nonattendees, the standardized prevalence ratio of use for each drug was calculated. An indirect standardization procedure using the attendees as reference was employed (ie, for the attendees the ratio between the observed number of users and the expected number was calculated, had they had the same age- and gender-specific prevalences as the nonattendees). A similar technique was used for the disease prevalences and for socioeconomic status. Age was categorized in 10-year bands. Confidence intervals for the standardized prevalence ratios were calculated by the method suggested by Morris and Gardner.2 To account for a possible nonrepresentativeness in our source population, we retrieved data on physician contacts, cardiovascular morbidity, and socioeconomic status in the four participating municipalities in our study and in Den-
24.e1
mark as a whole. Age-standardized prevalence ratios were calculated by the same method as described for the attendee vs. nonattendee analysis. The data source was Statistics Denmark. The comparison of socioeconomic status of the source population with the Danish population as a whole showed slightly more unemployed, early retired, and cash benefit recipients in the region studied (Supplemental Table 1). Likewise, there were fewer hospital admissions and fewer cases of ischemic heart disease and stroke in the population used as a basis for the study sample. The differences were, however, modest (Supplemental Table 2). Fifty percent of the invited population sample attended the survey. Comparison of attendees and nonattendees on the basis of previous hypertension related diagnoses, current medication, and socioeconomic variables showed slightly fewer diabetics in the group of attendees (Supplemental Table 3). Fewer cash benefit recipients and early retired accepted the invitation and employed did so slightly more often than not (Supplemental Table 4).
References 1. Gaist D, Sørensen HT, Hallas J. The Danish prescription registers. Dan Med Bull 1997;44:445– 48. 2. Morris JA, Gardner MJ. Calculating confidence intervals for relative risk, odds ratios and standardised ratios and rates. In: Gardner MJ, Altman DG, Statistics with confidence. London, England: British Medical Journal Publishing, 1989:60 –1.
Supplemental Table 1 The basis for the study population compared to the national population by socioeconomic parameters (%)
Urban residents Self-employed Employed Unemployed Early retired Cash benefit recipients
Denmark
Basis of population sample
Age-adjusted ratio
85 4.68 47.43 2.94 5.91 2.81
85 3.45 46.1 3.40 6.87 3.77
0.74 (0.73–0.76) 0.97 (0.97–0.98) 1.16 (1.14–1.18) 1.17 (1.15–1.18) 1.35 (1.32–1.37)
Supplemental Table 2 The basis for the study population compared to the national population by health related frequencies (events or registered diagnosis/100 persons/year)
Contacts to general practice Hospital admissions Hypertension Ischemic heart disease Stroke Diabetes
Denmark
Basis of population sample
Age-adjusted ratio
168.87 23.58 0.13 1.06 0.48 0.20
168.28 19.72 0.12 0.75 0.37 0.18
1.00 (0.99–1.00) 0.89 (0.88–0.90) 0.96 (0.82–1.11) 0.75 (0.71–0.80) 0.82 (0.75–0.88) 0.97 (0.86–1.09)
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Supplemental Table 3 Comparison of nonattendees and attendees by current use of hypertension related medication and diagnosis of hypertension related disease Characteristic Current use of Thiazides -blockers Calcium channel blockers Angiotensin-converting enzyme inhibitors or A2RA Any of the above Antidiabetics Low-dose aspirin Statins Any past diagnosis of Hypertension Diabetes Ischemic heart disease Cerebrovascular disease
Nonattendees (n ⫽ 7,866)
Attendees (n ⫽ 7,770)
Standardized prevalence ratio (CI)
242 (3.1%) 208 (2.6%) 188 (2.4%) 185 (2.4%)
268 (3.4%) 205 (2.6%) 173 (2.2%) 175 (2.3%)
1.07 (0.89–1.28) 0.92 (0.75–1.12) 0.98 (0.79–1.21) 0.85 (0.69–1.05)
602 (7.7%) 145 (1.8%) 129 (1.6%) 126 (1.6%)
611 (7.9%) 92 (1.2%) 110 (1.4%) 151 (1.9%)
0.96 (0.86–1.08) 0.60 (0.46–0.79) 1.00 (0.77–1.30) 0.94 (0.73–1.20)
202 (2.6%) 161 (2.0%) 160 (2.0%) 115 (1.5%)
191 (2.5%) 115 (1.5%) 157 (2.0%) 82 (1.1%)
0.91 (0.74–1.11) 0.66 (0.51–0.84) 1.04 (0.83–1.30) 0.78 (0.58–1.05)
CI, confidence interval. Supplemental Table 4 Comparison of nonattendees and attendees by socioeconomic factors for the 14,917 persons for whom data were available
Pensioners and others Unemployed Early retired Cash benefit recipients Employed Self-employed
Nonattendees (n ⫽ 7,341)
Attendees (n ⫽ 7,576)
Standardized prevalence ratio (95% confidence interval)
2530 (34% ) 238 (3% ) 422 (5% ) 273 (3% ) 3699 (50%) 179 (2%)
2266 (29%) 245 (3%) 280 (3%) 116 (1%) 4475 (59%) 194 (2%)
0.87 (0.84–0.89) 1.00 (0.91–1.09) 0.64 (0.59–0.70) 0.41 (0.36–0.47) 1.17 (1.15–1.20) 1.05 (0.95–1.16)