Journal of Human Hypertension (2004) 18, 73–78 & 2004 Nature Publishing Group All rights reserved 0950-9240/04 $25.00 www.nature.com/jhh
REVIEW ARTICLE
Trends in hypertension epidemiology in India R Gupta1,2 1
Department of Medicine, Monilek Hospital and Research Centre, Jawahar Nagar, Jaipur, India; 2Mahatma Gandhi National Institute of Medical Sciences, Sitapura, Jaipur, India
Cardiovascular diseases caused 2.3 million deaths in India in the year 1990; this is projected to double by the year 2020. Hypertension is directly responsible for 57% of all stroke deaths and 24% of all coronary heart disease deaths in India. Indian urban population studies in the mid-1950s used older WHO guidelines for diagnosis (BP X160 and/or 95 mmHg) and reported hypertension prevalence of 1.2–4.0%. Subsequent studies report steadily increasing prevalence from 5% in 1960s to 12–15% in 1990s. Hypertension prevalence is lower in the rural Indian population, although there has been a steady increase over time here as well. Recent studies using revised criteria (BP X140 and/or 90 mmHg) have shown a high prevalence of hypertension among urban adults: men 30%, women 33% in Jaipur (1995), men 44%, women 45% in Mumbai (1999), men 31%, women 36% in Thiruvananthapuram (2000), 14% in Chennai (2001), and men 36%, women 37% in Jaipur (2002). Among the rural populations, hypertension prevalence is men 24%, women 17% in Rajasthan (1994). Hypertension diagnosed by multiple examina-
tions has been reported in 27% male and 28% female executives in Mumbai (2000) and 4.5% rural subjects in Haryana (1999). There is a strong correlation between changing lifestyle factors and increase in hypertension in India. The nature of genetic contribution and gene– environment interaction in accelerating the hypertension epidemic in India needs more studies. Pooling of epidemiological studies shows that hypertension is present in 25% urban and 10% rural subjects in India. At an underestimate, there are 31.5 million hypertensives in rural and 34 million in urban populations. A total of 70% of these would be Stage I hypertension (systolic BP 140–159 and/or diastolic BP 90–99 mmHg). Recent reports show that borderline hypertension (systolic BP 130–139 and/or diastolic BP 85–89 mmHg) and Stage I hypertension carry a significant cardiovascular risk and there is a need to reduce this blood pressure. Population-based cost-effective hypertension control strategies should be developed. Journal of Human Hypertension (2004) 18, 73–78. doi:10.1038/sj.jhh.1001633
Keywords: epidemic; high blood pressure; hypertension; India
Global burden of hypertension Cardiovascular diseases account for a large proportion of all deaths and disability worldwide. Global Burden of Disease Study reported that in 1990, there were 5.2 million deaths from cardiovascular diseases in economically developed countries and 9.1 million deaths from the same causes in developing countries.1 However, whereas about one-quarter of all cardiovascular disease deaths occurred in persons who were less than 70 years of age in the developed world, more than about half of these deaths occurred in those less than 70 years in the developing world.2 It has been predicted that by the year 2020, there will be an increase by almost 75% in the global cardiovascular disease burden. Almost
Correspondence: Dr R Gupta, Department of Medicine, Monilek Hospital and Research Centre, Jawahar Nagar, Jaipur 302004, India. E-mail:
[email protected] Received 19 June 2003; revised and accepted 7 July 2003
all of this increase will occur in developing countries (Table 1). The situation in India is more alarming. It was reported that of a total of 9.4 million deaths in India in 1990, cardiovascular diseases caused 2.3 million deaths (25%). A total of 1.2 million deaths were due to coronary heart disease and 0.5 million due to stroke.1 It has been predicted that by 2020, there would be a 111% increase in cardiovascular deaths in India. This increase is much more than 77% for China, 106% for other Asian countries and 15% for economically developed countries.2 Control of the predicted increase in cardiovascular diseases will require modification of risk factors that have two characteristics. First, the risk factors must have a high attributable risk or high prevalence, or both. Second, most or all of the risks must be reversible cost effectively. Blood pressure (BP) is directly associated with risks of several types of cardiovascular disease, and the associations of BP with disease risk are continuous, indicating that large proportions of most populations have nonoptimal
Hypertension in India R Gupta 74 Table 1 Cardiovascular deaths by region in the years 1990 and 2020. Global Burden of Disease Study1,2 Cardiovascular deaths (1990) 6
Established market economies Former socialist economies India China Other Asia and Islands Sub-Saharan Africa Latin America and Caribbean Middle Eastern Crescent
No. ( 10 )
Due to CHD (%)
Due to stroke (%)
Predicted increase by 2002 (%)
3.2 2.1 2.3 2.6 1.3 0.8 0.8 1.3
53 50 52 30 34 26 44 47
25 31 20 50 29 47 32 16
15 26 111 77 106 114 120 129
BP values.3 Moreover, most or all BP-related risk appears to be reversible within a few years with inexpensive interventions. Hypertension is directly responsible for 57% of all stroke deaths and 24% of all coronary heart disease deaths in India.2 This fact is important because hypertension is a controllable disease and a 2 mmHg population-wide decrease in BP can prevent 151,000 stroke and 153,000 coronary heart disease deaths in India.2
Recent Indian studies Trends in hypertension prevalence in India have been reviewed in this journal and elsewhere.4,5 Studies have shown a high prevalence of hypertension in both urban and rural areas. Prevalence rates are almost similar to those in the USA. To determine the changing trends of hypertension prevalence in Indian urban and rural populations aged 20–70 years, we evaluated previous hypertension epidemiological studies (Table 2).3–5 Indian urban population studies in the mid-1950s used the standardised WHO guidelines for the diagnosis of hypertension (known hypertension or BP X160 mmHg systolic and/or 95 mmHg diastolic) and reported hypertension prevalence of 1.2–4.0%. Subsequent studies report steadily increasing hypertension prevalenceF4.35% in Agra (1961), 6.43% in Rohtak (1975), 15.52% in Bombay (1980), 14.08% in Ludhiana (1985), 10.99% in Jaipur (1995), 11.59% in Delhi (1997) and 13.1% in Chandigarh (1999) (w2 for trend ¼ 5.99, P ¼ 0.014). Statistical analysis shows a significant positive trend confirmed by nonparametric analysis (Mantel–Haenszel test, P ¼ 0.014) as well as regression analysis (r ¼ 0.70, P ¼ 0.026). Although there is generally a lower prevalence of hypertension in the rural Indian population, there has been a steady increase over time in this rural population as well. It has also increased over the yearsF0.52% in Bombay (1959), 1.99% in Delhi (1959), 3.57% in Haryana (1978), 5.41% in Delhi (1983), 5.59% in Rajasthan (1984), 2.63% in Punjab (1985), 4.02% in Maharashtra (1993), 3.41% in Maharashtra (1993), 7.08% in Rajasthan (1994) and Journal of Human Hypertension
3.58% in Haryana (1998) (w2 for trend ¼ 2.75, P ¼ 0.097). In South Indian rural subjects, that are almost urbanised, the prevalence has been reported to be as high as 17.8% (1993) and 12.46% (1994) in recent years. Overall, there is a significant increase in hypertension prevalence in rural areas although the rise is not as steep as in urban populations (r ¼ 0.67, P ¼ 0.025). On comparing the mean levels of BP from 1942 to 1995, it is seen that in urban men aged 40–49 years there is a significant increase in systolic BP (r ¼ 0.95, Po0.001) but not in diastolic (r ¼ 0.43, P40.2). This is of obvious clinical significance in light of the recent evidence that systolic BP is more closely linked to cardiovascular events and cardiac mortality.6 Systolic BP X140 mmHg and/or diastolic BP X90 mmHg is the currently accepted dividing line based on epidemiological and intervention studies.7 This level has been shown to be associated with increased cardiovascular risk in prospective cohort and case–control studies in USA and Europe. Framingham study reported that there was a continuum of risk of stroke and coronary heart disease with increasing diastolic BP and the levels where risks were not present were unknown.8 Stamler et al9 analysed US studies of correlation of BP levels with cardiovascular risks and showed that both systolic and diastolic BP have a continuous, graded, strong, independent and an etiologically significant relationship to the outcome variables such as cardiovascular mortality and all-cause mortality. No prospective studies similar to Framingham or other studies exist among Indians and, therefore, the level of BP where the risk of cardiovascular events increases is not well defined. Most of the studies from developing countries show a lower mean population BP as compared to developed countries.10–12 Therefore, the population norms as well as the values above which high BP causes vascular risk could be lower in these countries.12 However, in the absence of prospective data and also because of the current recommendations of the World Health Organisation7 and many Indian Consensus Groups, we shall accept the criteria of systolic X140 mmHg and/or diastolic X90 mmHg as the cut-off level for the diagnosis of hypertension.
Hypertension in India R Gupta 75 Table 2 Indian hypertension prevalence studies (BP X160/95)4 First author
Year
Age group
Place
Sample size
Urban Dotto BB Dubey VD Sathe RV Mathur KS Malhotra SL Gupta SP Dalal PM Sharma BK Gupta R Chadha SL Thakur K
1949 1954 1959 1963 1971 1978 1980 1985 1995 1998 1999
18–50 18–60 20–80 20–80 20–58 20–69 20–80 20–75 20–80 25–69 30–80
Calcutta Kanpur Bombay Agra Railways Rohtak Bombay Ludhiana Jaipur Delhi Chandigarh
Rural Shah VV Padmavati S Gupta SP Wasir HS Baldwa VS Sharma BK Kumar V Joshi PP Jajoo UN Gupta R Chadha SL
1959 1959 1977 1983 1984 1985 1991 1993 1993 1994 1998
30–60 20–75 20–69 20–69 21–60 20–75 21–70 16–60 20–69 20–80 25–69
Bombay Delhi Haryana Delhi Rajasthan Punjab Rajasthan Maharashtra Maharashtra Rajasthan Delhi
Prevalence (%7s.e.)
2500 2262 4120 1634 4232 2023 5723 1008 2212 13134 1727
1.2470.2 4.2470.4 3.0370.3 4.3570.5 9.2470.4 6.4370.5 15.5270.5 14.0871.1 10.9970.7 11.5971.0 13.1171.0
5996 1052 2045 905 912 3340 6840 448 4045 3148 1732
0.5270.1 1.9970.4 3.5770.4 5.4170.8 5.5970.8 2.6370.3 3.8370.2 4.0270.9 3.4170.3 7.0870.5 3.5870.5
Table 3 Recent Indian hypertension prevalence studies (BP X140/90) First author
Year
Age group
Place
Urban Gupta R13 Gupta PC14 Joseph A15 Anand MP18 Mohan V16 Gupta R17
1995 1999 2000 2000 2001 2002
20–75 18–60 20–89 30–60 20–70 20–75
Jaipur Mumbai Trivandrum Mumbai Chennai Jaipur
Rural Gupta R19 Malhotra P20
1994 1999
20–75 16–70
Rajasthan Haryana
Sample size
Prevalence (%)
Men
Women
Men
Women
1415 40067 76 1521 518 550
797 59522 130 141 657 573
29.5 43.8 31.0 34.1a 14.0a 36.4
33.5 44.5 41.2
1982 2559
1166
23.7 3.0
16.9 5.8b
37.5
a
Gender-specific data not available. Prevalence rates based on multiple examinations.
b
In this article, we shall focus on recent Indian studies (Table 3). The prevalence of hypertension defined by the recent World Health Organisation criteria has been reported among some urban Indian populations. Gupta et al13 reported hypertension in Jaipur in 30% men and 33% women aged X20 years. Gupta et al14 reported hypertension in 44% men and 45% women in Mumbai, Joseph et al (2000)15 reported it in 31% men and 41% women in Trivandrum, while Mohan et al16 reported an age-adjusted prevalence of 14% in Chennai. Gupta et al17 reported its prevalence in 36% men and 37% women in Jaipur. Anand18 reported hypertension in 34.1% middle-class executives in Mumbai, but after multiple BP measurements, it was confirmed in 26.8% male and 27.6% female
officers. These findings are in consonance with other regions of Asia where it has been reported that, at any one time, about half of all individuals have high BP.2 Among the rural populations, hypertension prevalence using recent criteria was first reported by Gupta et al (1994)19 in subjects aged X20 years. Hypertension was present in 24% men and 17% women. The prevalence of hypertension diagnosed on the basis of multiple blood pressure measurements was reported by Malhotra et al,20 who reported it in 3.5% men and 5.8% women in Haryana adults aged 16–70 years; this low prevalence was attributed to very low body-mass index in this population. Is hypertension prevalence increasing in India? Meta-analysis of previous Indian prevalence studies Journal of Human Hypertension
Hypertension in India R Gupta 76
Figure 1 Age-specific hypertension prevalence (%) in an urban Indian population in the years 199513 and 2002.17 No significant change in the prevalence at any age group is observed (P40.05).
has shown that there has been a significant increase in hypertension in both urban and rural areas (Table 2). This increase is associated with increasing mean systolic BP levels. These studies were widely distributed in time and the methodologies were different. Observer bias cannot be excluded. We performed successive cross-sectional studies to determine the change in BP levels and hypertension prevalence in Jaipur.13,17 In 1995, the overall prevalence of hypertension in adults 420 years was 30% in men and 33% in women, while in 2002 the age-adjusted prevalence was 30% in men and 34% in women (P ¼ NS). Age-specific prevalence rates are shown in Figure 1 and no significant differences are seen. These results show that over a short-term of 7 years, there is no significant change in hypertension prevalence in an urban Indian population. The mean BP levels also did not change.12,17 Possibly, a longer time is needed to effect changes in a given population. Prospective cohort studies within a population are needed to answer these questions as multiple factors are involved in hypertension variation in epidemiological studies.
Genetic or environmental influences Although the precise reasons for the increase in hypertension prevalence among Indians is not established, several possibilities exist. Studies among the unacculturated societies have shown lower BP levels that are not influenced by age.21 Data show that among the so-called unacculturated and less-cultured Indian rural populations, there is only a small increase in prevalence in hypertension over the years.4 On the other hand, in urban populations that are being exposed to stress of acculturation and modernisation, the hypertension prevalence rates have more than doubled in the last 30 years. Significant hypertension risk factors are genetic and environmental (Table 4). There are a large Journal of Human Hypertension
number of genes that are responsible for hypertension. Single-gene-related hypertension is, however, rare. Intermediate phenotypes are more important and prevalent than gene mutations. These phenotypes are familial dyslipidaemia, metabolic syndrome, insulin resistance, body-fat distribution, kallikrein deficiency, sodium sensitivity, nonmodulation of aldosterone and renal blood flow, abnormal cellular ion transport systems (Na, Li, K, H transport systems) and BP reactivity. The nature of the genetic contribution to hypertension needs more studies among Indians.3 Population and animal studies suggest a polygenic or oligogenic model for hypertension, wherein susceptibility imparted by any single gene is modest and quantitative.21 Such genetic variations would be expected to modulate response to environmental exposure and may only achieve significance through cumulative integration of lifetime experiences. Although this scenario greatly complicates the task of genetic epidemiologists, major studies are currently underway and are likely to produce a list of common genes contributing to hypertension. Essential hypertension may be considered to be the result of interactions between genes and environment.4,22 The environmental effects are powerful and explain most of the BP differences between populations.22 Obesity, especially truncal obesity, is a powerful influence because of the associated insulin resistance that often leads to cardiovascular dysmetabolic syndrome and is associated with hypertension. Other important environmental factors are smoking, alcohol intake, physical inactivity, dietary excess of sodium and fat and deficiency of potassium and fibre intake and psychosocial stress. There is epidemiological evidence that population demographic changes in India have increased hypertension risk factors. There is increasing life expectancy, urbanisation, development and affluence in India.23 In 1901, only 11% of the population was living in an urban area; this proportion was 17.6% in 1951, 18.3% in 1961, 20.2% in 1971, 23.7% in 1981 and 26.1% in 1991. There is a strong correlation between urbanisation and increase in hypertension prevalence (r ¼ 0.92, Po0.01). Affluence, as measured by evaluation of per capita net domestic product, growth of production and human development index, has also increased sharply in India in the recent years and correlates positively with the hypertension increase. Tobacco production, which is a surrogate for its consumption, is increasing at a very high rate in India. The per capita fat and oil consumption has also increased in the last 40 years. It was 5.79 kg/person/year in 1961, 5.85 in 1971, 6.48 in 1981 and 6.96 in 1987. Salt consumption was 10.7 g/person/day in 1971 and increased to 13.0 in 1981, 15.8 in 1991 and 16.9 in 1994. We hypothesise that the summation of these sociodemographic and lifestyle factors is accelerating the hypertension epidemic currently sweeping India and other developing countries. The gene–
Hypertension in India R Gupta 77 Table 4 Hypertension risk factors Single gene mutations Angiotensinogen gene Glucorticoid receptor Lipoprotein lipase Glucocorticoid remediable aldosteronism (GRA) Apparent mineralocorticoid excess Congenital adrenal hyperplasia Polycystic kidney disease Liddle’s syndrome Gitelman’s syndrome Genetic factors (possible polygenic influences) Angiotensinogen and angiotensin-converting enzyme Renin binding protein Sympathetic b2 and a2 receptors Low transforming growth factor b1 a-adducin protein Atrial natriuretic factor Insulin receptor Intermediary phenotypes (multiple genes) Sympathetic nerve activity, blood pressure reactivity Sodium sensitivity Renin–angiotensin–aldosterone system Renal kallikrein–kinin system Endothelial factors Cellular ion-transport systems (Na–Li; Na–H; Na–K–Cl) Thrifty genotype Insulin resistance Metabolic syndrome (hypertension, insulin resistance, dyslipidaemia) Cardiac output Environmental factors Obesity, truncal obesity Alcohol intake Smoking and tobacco intake High salt intake Low dietary potassium or calcium intake Low birth weight Temperature and altitude Psychosocial stress Sedentary lifestyle Socioeconomic status
environment interaction in accelerating the hypertension epidemic needs more studies.
Epidemiological studies and implications for treatment The Treatment of Mild Hypertension Study (TOMHS)24 showed that lowering of mildly raised BP (Stage I hypertension: systolic 140–159 and/or diastolic 90–95 mmHg) by drugs was associated with improved outcome as compared to the placebo group. In the multiple risk factor intervention trial (MRFIT),9 there was an excess of mortality at systolic BP 4110 mmHg, although statistical significance was achieved at BP of 4120 mmHg. Stamler25 commented that an average population systolic BP of 110 mmHg is a realistic goal. In India, we need to examine the absolute numbers of patients with hypertension who would be eligible for treatment if we employ these recommendations.
Epidemiological studies have shown that hypertension is present in 25% of urban and 10% of rural subjects in India. There is a difference in measurement methodology of BP in epidemiological studies as compared to clinic-based measurements. It has been reported that epidemiological studies that rely on single-session measurements overdiagnose hypertension by 20–25%.18 If we discount this proportion, 19% adults in the urban and 7.5% in the rural areas shall be eligible for hypertension therapies. Translating these proportions into numbers reveals a massive burden of this disease in India. According to the 2001 census, there are 600 million adults in India, of whom 420 million are in rural and 180 million in urban areas and the absolute number of hypertensives in India shall be 31.5 million rural and 34 million urban subjects, a total of 65.5 million. An Indian epidemiological study reported that 70% of these would be Stage I hypertension (systolic BP 140–159 and/or diastolic BP 90– 99 mmHg).26 The Stage I hypertension (45.5 million subjects) can be managed initially by lifestyle measures. However, recent reports from the Seven Countries Study27 and Framingham Study28 show that borderline hypertension (systolic BP 130–139 and/or diastolic BP 85–89 mmHg) and Stage I hypertension carries a significant cardiovascular risk and there is a need to reduce this BP. Pharmacological therapies in this class of individuals need more studies, although TOMHS demonstrated that it is helpful in reducing cardiovascular end-points.24 For Stages 2 and 3 hypertension multiple studies recommend pharmacological therapy and, therefore, 20 million persons in India belonging to this class require regular antihypertensive medications. This carries a huge economic burden on the already overstressed Indian economy. Studies that examine cost-effective approaches to control BP optimally among Indians are needed.
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