Hypertension increased the risk of stroke threefold among both men and women in every age group monitored in the Framingham study.[ 82] A statistical overview of prospective epidemiological studies of middle-aged individuals with no previous history of vascular disease, examining the relationship between diastolic blood pressure and stroke, showed a doubling of the risk of stroke for every 7.5 (mm Hg) rise in blood pressure.[83] Similarly, among East Asians, projections indicate that a population-wide reduction in diastolic blood pressure of 3mm Hg would reduce stroke mortality by one-third.[79] In the PRC, carefully conducted epidemiological studies revealed a north–south gradient in stroke mortality and incidence that was shown to be due mainly to differences in the prevalence of hypertension, which was higher in the northern provinces.[6] The highest prevalence of hypertension was 22.3 percent in the province of Tibet, and the lowest was 4.8 percent in the province of Qinghai. A 10 percent higher prevalence of hypertension was associated with a 2.8-fold higher incidence of stroke, even after adjustment for differences in prevalence of cigarette smoking and alcohol consumption.[ 6,46]

Hypertension is a major public health problem in African countries, where it may affect up to 10 percent of the population and contributes to coronary heart disease, as well as to hemorrhagic and thrombotic stroke. Studies from Nigeria, Ivory Coast, and Zimbabwe found hypertension to be the main risk factor for both ischemic and hemorrhagic stroke.[ 22,72,77] The condition frequently goes unrecognized, however, in part because many African health care providers lack reliable equipment for measuring blood pressure.[27]

The results of controlled clinical trials of treatments for hypertension in developed populations may inform research in the developing world. Clinical studies in developed populations indicate that blood pressures of less than 140/83 mm Hg are optimal for stroke prevention. Therefore, the goal of antihypertensive therapy should be to normalize rather than just reduce blood pressure.[84] Additionally, recent studies and resulting data from both developed and developing countries indicate that high systolic blood pressure is equally or more important, especially in older adults (over age 65), as a predictor for stroke.[85,86,87,88,89 and 90] Antihypertensive therapy for systolic hypertension will be important for reducing the risk of stroke in elderly populations. Antihypertensive therapy has been found to reduce the risk of stroke by about 42 percent in people younger than age 65 suffering from high blood pressure.[ 88] Unfortunately, studies of patients who received antihypertenstion medication through urban clinics in both South Africa [89] and Saudi Arabia [91] indicate that many patients who receive the medication use it incorrectly, and few recognize that uncontrolled hypertension can lead to stroke.

Several studies in developed countries—notably the Framingham study [82] and the Honolulu Heart Study [92]—have documented diabetes as a risk factor for stroke. The Framingham study found a 10 percent increase in risk for having a