Q J Med 2001; 94: 391-396
© 2001 Association of Physicians
Commentary |
Ethnic differences in hypertension and blood pressure control in the UK
From the University Department of Medicine, City Hospital, Birmingham, UK
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Introduction |
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 Top Introduction Hypertension and ethnicity in...Treatment and control of...Clinical implicationsConclusionsReferences |
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Hypertension is a major risk factor for cardiovascular and cerebrovascular disease, the major causes of death in the UK and other Western countries. Despite this, many patients with hypertension remain undetected and inadequately treated. In order to accurately assess the effectiveness of health programmes aimed at hypertension, it is important first, to establish the mean blood pressure (BP) levels and the prevalence of hypertension in a population, particularly amongst the different ethnic groups, and second, to determine the proportion of people achieving adequate BP control (defined as BP <140/95 mmHg) on anti-hypertensive medication, given the risk of cardiovascular mortality and morbidity associated with high blood pressure.
Nevertheless, the epidemiological data on ethnic differences in BP and hypertension prevalence in the UK are conflicting. Detection, treatment, and control of hypertension among the three main ethnic groups in the UK is important, given that recent studies indicate substantial ethnic differences in cardiovascular mortality.1 For example, compared to Caucasians, Afro-Caribbeans and people of African descent have a higher incidence of stroke2 and end-stage renal failure,3 whereas coronary artery disease is less common. Conversely, South-Asians (defined as people originating from the Indian subcontinent and East Africa) have a higher incidence of coronary heart disease.2
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Hypertension and ethnicity in the UK |
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TopIntroductionHypertension and ethnicity in...Treatment and control of...Clinical implicationsConclusionsReferences |
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With advancing age, the prevalence of hypertension increases. In the Health Survey for England, for example, the prevalence of hypertension was 3.3% in those aged <40 years, 27.9% in those aged between 40 and 79 years, and 49.9% in those aged 80 years and older.4 Clearly, ‘hypertension’, currently defined as BPs >140 mmHg (systolic) and/or 90 mmHg (diastolic), is a common problem.4
Several population-based studies in the UK have investigated ethnic differences in BP, in order to explain the variability in cardiovascular disease (CVD) mortality and morbidity5–15 (Table 1
).
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Most studies have reported a higher prevalence of hypertension among Afro-Caribbean populations6–7,9,11,13–15 and among South Asians.12–15 In addition, the majority of these studies have also reported significantly higher mean BP levels amongst both Afro-Caribbean populations9–11,14,15 and South Asian men9–10,14,15 compared to their White counterparts. However, other studies have failed to find significant differences in mean BPs among the three main ethnic groups in the United Kingdom,6–8,12 whilst the study by Meade et al.5 reported mixed findings, with significant differences in mean BP between Afro-Caribbean and White day shift workers but no significant differences amongst the night shift workers.
Therefore, the data regarding elevated BP and a greater prevalence of hypertension among ethnic groups in the UK is not as consistent as data from the US, where virtually every population-based study has reported higher mean BPs at all ages, with a greater prevalence of hypertension, among African-Americans compared to White Americans.16,17 The precise reasons for the inconsistency in the data from studies of ethnic groups in the UK are uncertain, but may partly relate to the different populations studied and the fact that the UK ethnic population is predominantly first-generation.
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Treatment and control of hypertension in the UK |
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TopIntroductionHypertension and ethnicity in...Treatment and control of...Clinical implicationsConclusionsReferences |
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The ‘rule of halves’ suggests that only 50% of hypertensives are diagnosed, of which only 50% are treated, and of these, only 50% are well controlled: thus, perhaps only 12.5% of those with high BP receive anti-hypertensive therapy and achieve adequate BP control,4 but this low figure may have improved somewhat, at least in Western countries.18 Since the introduction of the National High Blood Pressure Education Program by the National Institutes of Health in the US in 1973, hypertension awareness rates have gradually improved from 51% to 73%, treatment rates from 31% to 55%, and control rates (BP <140/90 mmHg) from 10% to 29%, between the 1976–1980 National Health and Nutrition Examination Survey (NHANES II) to the 1988–1991 survey (NHANES III, Phase I), with dramatic reductions in stroke (60%) and CHD (53%) mortality.19
The first nationwide survey of the management of hypertension in England, using data from the Health Survey for England 1994, of adults aged 16 years and older, reported that 19.5% were hypertensive (defined as SBP 
160 mmHg, and/or DBP 95 mmHg, or anti-hypertensive treatment).20 Among the hypertensives, only 66% of women and 60% of men had been told they had high blood pressure previously. Approximately half of all hypertensives were receiving treatment (54.4% of women vs. 44.8% of men), and of these, 59% achieved adequate BP control (defined as BP <160/95 mmHg). Based on a more stringent definition of hypertension (SBP 140 mmHg, and/or DBP 90 mmHg),21 the analogous rates for awareness, treatment, and control were 40%, 26%, and 6%, respectively.20 However, although awareness, treatment, and control rates have improved, the majority of hypertensives still achieve inadequate BP control or receive no anti-hypertensive treatment at all.19–20
Very few studies investigating ethnic differences in BP have reported treatment and control rates among these subgroups: surprisingly, given the increased risk of death from stroke and end-stage renal failure among Afro-Caribbeans and people of African descent, and CHD mortality among those of South-Asian origin. However, those which do, reveal that treatment and control rates vary considerably by sex and ethnic group.7,9,11,13–15 There is also some evidence that the rates of detection, treatment, and control are higher among Black populations in Britain,11,13–15 indicating a greater awareness among the general public and physicians of the importance of detecting and managing hypertension, particularly in Black populations. It appears that rates of detection, treatment, and control of high BP among people of South Asian origin may be similar to those of the White population.9,14–15
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Clinical implications |
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TopIntroductionHypertension and ethnicity in...Treatment and control of...Clinical implicationsConclusionsReferences |
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What are the implications of ethnic differences in blood pressure and the prevalence of hypertension? Black populations respond differently to certain anti-hypertensive drugs compared to White patients. The majority of trials have shown that Black patients respond less well to monotherapy with drugs that suppress the renin-angiotensin system—the beta-blockers, angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor antagonists—whereas they respond equally well or better to alpha-antagonists, calcium-channel blockers, and diuretics.22,23
Randomized controlled trials have shown that diuretics reduce hypertension-related morbidity and mortality in Black as well as in White populations, but there is evidence of a greater decrease in BP among hypertensive Black patients when compared to White patients when they receive an equivalent dose of a diuretic.24 These enhanced therapeutic effects have been related to increased ‘salt sensitivity’, low renin activity, reduced Na+K+-ATPase activity, and relative expansion of plasma volume. Beta-blockers, ACE inhibitors and angiotensin receptor antagonists are generally less effective as monotherapy in Black hypertensives16,25 because of the tendency towards a low-renin state and a lower cardiac output, with increased peripheral resistance. However, in situations where a beta-blocker or an ACE-inhibitor is indicated, such as post-myocardial infarction, the use of high doses and/or the addition of a diuretic improves the BP response in Black populations.26,27 Calcium channel blockers are also extremely effective antihypertensive drugs in Black patients.22 However, there is limited information to date about the efficacy and tolerability of angiotensin receptor antagonists in Black patients. One subgroup analysis of patients treated with valsartan suggests that the latter may reduce mean BP, but the mean reduction is less than that seen for other ethnic groups.28
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Conclusions |
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TopIntroductionHypertension and ethnicity in...Treatment and control of...Clinical implicationsConclusionsReferences |
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Reduction of BP is one of the most important challenges facing medicine and public health in the next 20 years, given that the World Health Organization estimates that disability and mortality as a result of CHD and cerebrovascular disease will rank first and fourth, respectively, as causes of the global disease burden.29 Ethnicity is an important consideration in the management of BP, given the ethnic differences in the prevalence, treatment, and control of hypertension, differing responses to anti-hypertensive medication, and substantial ethnic differences in CVD mortality attributable to hypertension.
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Notes |
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Address correspondence to Dr G.Y.H. Lip, University Department of Medicine, City Hospital, Dudley Road, Birmingham B18 7QH. e-mail: g.y.h.lip{at}bham.ac.uk
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References |
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TopIntroductionHypertension and ethnicity in...Treatment and control of...Clinical implicationsConclusionsReferences |
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