Epidemiology of stroke in India

Several population-based surveys on stroke were conducted from different parts of India. During the last decade, the age-adjusted prevalence rate of stroke was between 250-350/100,000. Recent studies showed that the age-adjusted annual incidence rate was 105/100,000 in the urban community of Kolkata and 262/100,000 in a rural community of Bengal. The ratio of cerebral infarct to hemorrhage was 2.21. Hypertension was the most important risk factor. Stroke represented 1.2% of total deaths in India. Neurology Asia 2006; 11 : 1 – 4 Address correspondence to: Dr Tapas Kumar Banerjee, National Neurosciences Centre Calcutta, Peerless Hospital Campus, 360 Panchasayar, Garia, Kolkata700094, India. Phone: 91-33-2432-0777/0999, Fax: 91-33-2432-0682, E-mail: [email protected] INTRODUCTION After coronary heart disease (CHD) and cancer of all types, stroke is the third commonest cause of death worldwide. However unlike the Caucasians, Asians have a lower rate of CHD and a higher prevalence of stroke.1 Among the Asians, the number who died from stroke was more than three times that for CHD.2-4 In one report, the agestandardized, gender-specific stroke mortality rate was 44 to 102.6/100,000 for Asian males, compared with only 19.3 for Australian white males.5 In the early 1980s the prevalence rates of stroke were around 500-700 per 100,000 in the western countries6 and 900 per 100,000 in Asia.7 The disparity between the stroke and CHD incidence rates is usually attributed to high prevalence of hypertension and low levels of blood lipids among the Orientals.8 Hypertension was related to high salt intake and perhaps to genetic factors and low serum lipid was due to low levels of animal fats and protein in oriental diet. The above epidemiological data among Asians is based upon surveys carried out in the Chinese population. Among the native Japanese, the three consecutive decades following World War II witnessed stroke as the commonest cause of death. But in the recent two decades, there had been a substantial reduction of stroke mortality. By 1985, CHD became commoner than stroke as the cause of death among the Japanese.8 This change in mortality profile paralleled the change in dietary pattern, with the current Japanese diet showing increase in animal fat and animal protein and reduction in the amount of common salt.9 Intracerebral hemorrhage occurs several times more frequently in the Japanese than in US whites or blacks. Besides, there is predominance of intracranial atherosclerotic disease in Japanese. This is in contrast to the pattern in white Americans, where extracranial arteries are the focus of the majority of atherosclerotic occlusive disease.9 Apart from Chinese and Japanese, comprehensive epidemiological data of stroke among the other races in Asia is still sparse. A recent study comparing stroke disorders among three Asian races in Singapore revealed that Chinese had higher prevalence of stroke when compared to Indians and Malay Singaporeans.10 In India, several epidemiological studies11 have been undertaken in different parts of the country since the eighties. Most of these populationbased surveys however, were cross-sectional and determined the prevalence rates of stroke in the communities. This article is an overview of the major epidemiological surveys on stroke reported in India. STROKE PREVALENCE, INCIDENCE AND SUBTYPES The first community-based study on stroke was carried out in and around the town of Vellore in South India12 during the period 1969-71, followed by the study in Rohtak in North India13 during 1971-74. Subsequently there was a spate of REVIEW ARTICLE Neurology Asia June 2006 2 Table 1. The prevalence rates of stroke from various major epidemiological studies in India Zone Place Rural/ Year Population Crude Age adjusted urban prevalence prevalence