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Hypertension & pre-hypertension in developing countries.

Hypertension is reported to be the fourth contributor to premature death in developed countries and the seventh in developing countries (1). Recent reports indicate that nearly 1 billion adults (more than a quarter of the world's population) had hypertension in 2000, and this is predicted to increase to 1.56 billion by 2025 (2). Earlier reports also suggest that the prevalence of hypertension is rapidly increasing in developing countries (3,4) and is one of the leading causes of death and disability in developing countries.

The epidemiology of hypertension, in terms of its importance as a risk factor for cardiovascular diseases, continues to be a major area of research. In 1913, it was reported that patients with elevated blood pressure (BP) tend to die prematurely, while in 1931 high BP was a common problem in clinical practice in Britain (5,6). A meta-analysis of hypertension prevalence rates in India (7) demonstrated a significant increase in the prevalence of hypertension. The increase was significantly higher in urban than in rural populations and the prevalence of hypertension was higher in urban compared to rural areas. The prevalence rates in India are now almost comparable to those in the USA (8,9). The prevalence of hypertension varies considerably from one region of India to another. Yet no nationwide epidemiological studies to determine the prevalence of hypertension have been carried out. Sporadic studies from different parts of the country provide data on the epidemiology of hypertension in India. Chopra & Chopra (10) reported the first epidemiological study on hypertension in urban north India in 1942, following which, many studies in urban and rural areas of India have been carried out. Subsequent studies have shown a steadily increasing trend of hypertension in India (11).

Indian urban population studies in the mid-1950s used the standardized World Health Organization (WHO) guidelines (hypertension diagnosed if systolic BP [is greater than or equal to] 160 and/or diastolic BP [is greater than or equal to] 95 mm Hg) (12), have shown increasing trend in hypertension prevalence. Studies from Agra (1963) (13) and Rohtak (1978) (14) using WHO criteria showed prevalence 4.35 and 6.43 per cent respectively. A majority of the surveys in urban areas using the criteria of [is greater than or equal to] 160/95 mmHg, showed a prevalence rate of 6-13 per cent, except a few, which reported a prevalence of 15 per cent (15,16). The Jaipur Heart Watch study (17) and the Chennai Urban Rural Epidemiology Study (CURES) (18) reported the prevalence of hypertension to be 37 and 20 per cent using the JNC- VI/VII guidelines (hypertension diagnosed if systolic BP [is greater than or equal to] 140 and/or diastolic BP [is greater than or equal to] 90 mm Hg) (19,20). The recent inclusion of the term 'prehypertension' (defined as the blood pressure range of 120 to 139 mm Hg systolic or 80 to 89 mm Hg diastolic) heralds the onset of arterial hypertension and thus may be considered a starting point in the cardiovascular disease continuum. Moreover, pre-hypertension has been associated with higher cardiovascular risk and is estimated to decrease the average life expectancy by as much as five years (20,21). However, this term is highly controversial and many people suggest dropping this term. Indeed there are some who do not even like the idea of having an arbitrary cut-off point to define 'hypertension' as they feel that BP like cholesterol is a continuum of risk (20).

In the light of published data suggesting increase in prevalence of hypertension in developing countries, the study by Yadav et al in this issue (22) conducted in 1112 adults (age >30 yr) explores the prevalence of pre-hypertension and hypertension, as well as their association with cardiovascular risk factors, in an Indian upper socio-economic population residing in an urban colony in the city of Lucknow, north India. The authors have reported a similar age and sex adjusted prevalence of hypertension and pre-hypertension (32%) in their population. The prevalence of hypertension and pre hypertension were higher in males when compared to females, an increasing trend was observed in both males and females with increasing age. Increasing age, body mass index, waist-hip ratio and the presence of diabetes or impaired glucose tolerance (IGT) were independent risk factors for both pre-hypertension and hypertension. The prevalence rate of hypertension reported in this study was similar to that reported among employees aged 2059 yr of a large industry near Delhi (30%) (23). However, the prevalence rate of pre-hypertension was 44 per cent in the Delhi industrial population and 36.1 per cent in the Chennai urban population (18), which are much higher than that reported in this study (32%). Very few studies have looked at the prevalence of pre-hypertension in India. Recently, two studies conducted in the Chinese (n=15,540) and Turkish (n=4809) population reported an overall prevalence of pre-hypertension to be 21.9 and 14.5 per cent respectively (24,25). Compared to other population, the pre-hypertension prevalence rate is higher among affluent urban Indians. As rightly commented by Joshi & Parikh (26), with the current rate of hypertension, India will have the largest number of people with hypertension in the world, with the potential of becoming the 'Hypertension capital of world!'

Data of study by Yadav et al (22) suggest that the prevalence of hypertension in the youngest age group (30-39 yr) was 13.7 per cent and increased to a peak of 64 per cent in the age group 60-69 yr, while prevalence of pre-hypertension was highest in the group 30-39 yr (36%). A similar prevalence of pre-hypertension in the same age group (35.4%) has been reported by our group in the Chennai urban population (18). The present finding, of very high prevalence rates of pre-hypertension in younger age group is alarming, as they may develop hypertension as this population ages. The prevalence of hypertension will increase even further unless broad and effective preventive measures are implemented at this stage as India is a vast country with a heterogeneous and young population.

Thus, it is clear that the prevalence of hypertension between three and six decades in India, has increased by about 30 times among urban residents and by about 10 times among the rural residents. Various factors might have contributed to this rising trend, attributable to several indicators of economic progress such as increased life expectancy, urbanization and its attendant lifestyle changes including increasing salt intake and the overall epidemiologic transition India is experiencing currently. Epidemiological studies to assess the prevalence of hypertension are urgently needed in developing countries like India to determine the baseline against which future trends in risk factor levels can be assessed and preventive strategies planned to promote health among all sections of the populations including reducing obesity, increasing physical activity, decreasing the salt intake of the population and a concerted effort to promote awareness about hypertension, its risk factors, and risk behaviours. These efforts have the potential to reduce the emergence or minimize the prevalence of pre-hypertension and hypertension in different regions of India.

References

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(2.) Kearney PM, Whelton M, Reynolds K, Muntner P, Whelton PK, He J. Global burden of hypertension: analysis of worldwide data. Lancet 2005; 365 : 217-23.

(3.) Reddy KS. Hypertension control in developing countries. Genetic issues. J Hum Hypertens 1996; 10 : S33-8.

(4.) Nissinen A, Bothig S, Granroth H, Lopez AD. Hypertension in developing countries. World Health Stat Q 1988; 41 : 141-54.

(5.) Janeway TC. A clinical study of hypertensive cardiovascular disease. Arch Intern Med 1913; 12 : 755-80.

(6.) Hay J. The significance of a raised blood pressure. BMJ 1931; ii: 43-7.

(7.) Gupta R. Meta-analysis of prevalence of hypertension in India. Indian Heart J 1997; 49 : 43-8.

(8.) Expert Group. The Fifth Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure. Arch Intern Med 1993; 153: 154-86.

(9.) Whelton PK. Epidemiology of hypertension. Lancet 1994; 344: 101-6.

(10.) Chopra RN, Chopra GS. A study of normal blood pressure in Indians. Indian Med Gaz 1942; 77 : 21-2.

(11.) Gupta R. Trends in hypertension epidemiology in India. J Hum Hypertens 2004; 18 : 73-8.

(12.) World Health Organization- Hypertension and coronary heart disease: classification and criteria for epidemiological studies. WHO Tech Rep Ser 1959; 168 : 1-28.

(13.) Mathur KS, Sapru RP. The aetiology and incidence of heart disease--a changing pattern over the fifteen year period 1947 to 1961. J Assoc Physicians India 1963; 11 : 651-9.

(14.) Gupta SP, Siwach SB, Moda VK. Epidemiology of hypertension. Based on total community survey in the urban population of Haryana. India Heart J 1978; 30 : 315-22.

(15.) Malhotra SL. Dietary factors causing hypertension in India. Am J Clin Nutr 1970; 23 : 1353-63.

(16.) Dalal PM. Community survey of hypertension in "old" Bombay. In: Thurm RH, editor. Essential hypertension. Miami: Symposia Specialists; 1979. p. 35-41.

(17.) Gupta R, Gupta VP, Sarna M, Bhatnagar S, Thanyi J, Sharma V, et al. Prevalence of coronary heart disease and risk factors in an urban Indian population: Jaipur Heart Watch-2. V. Indian Heart J 2002; 54:59-66.

(18.) Mohan V, Deepa M, Farooq S, Datta M, Deepa R. Prevalence, awareness and control of hypertension in Chennai--the Chennai Urban Rural Epidemiology Study (CURES-52). J Assoc Physicians India 2007; 55 : 326-32.

(19.) The Sixth Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure. Arch Intern Med 1997; 157 : 2413-46.

(20.) Chobanian AV, Bakris GL, Black HR, Cushman WC, Green LA, Izzo JL, et al. The seventh report of the Joint National Committee on Prevention, Detection, Evaluation and Treatment of High Blood Pressure the JNC-7 Report. JAMA 2003; 289 : 2560-72.

(21.) Russell LB, Valiyeva E, Carson JL. Effects of prehypertension on admissions and deaths: a simulation. Arch Intern Med 2004; 164 : 2119-24.

(22.) Yadav S, Boddule R, Genitta G, Bhatia V, Bansal B, Kongara S, et al. Prevalence & risk factors of pre-hypertension & hypertension in an affluent north Indian population. Indian J Med Res 2008; 128 : 712-20.

(23.) Prabhakaran D, Shah P, Chaturvedi V, Ramakrishnan L, Manhapra A, Reddy KS. Cardiovascular risk factor prevalence among men in a large industry of northern India. Natl Med J India 2005; 18 : 59-65.

(24.) Yu D, Huang J, Hu D, Chen J, Cao J, Li J, et al. Prevalence and risk factors of prehypertension among chinese adults. J Cardiovasc Pharmacol 2008; 52 : 363-8.

(25.) Erem C, Hacihasanoglu A, Kocak M, Deger O, Topbas M. Prevalence of prehypertension and hypertension and associated risk factors among Turkish adults: Trabzon Hypertension Study. J Public Health (Oxf). 2008.

(26.) Joshi SR, Parikh RM. India--diabetes capital of the world: now heading towards hypertension. J Assoc Physicians India 2007; 55 : 323-4.

R. Pradeepa & V. Mohan *

Dr Mohan's Diabetes Specialities Centre & Madras

Diabetes Research Foundation

Chennai 600 086, India

* For correspondence: drmohans@vsnl.net
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Title Annotation:Commentary
Author:Pradeepa, R.; Mohan, V.
Publication:Indian Journal of Medical Research
Article Type:Report
Geographic Code:9INDI
Date:Dec 1, 2008
Words:1832
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