Hypertension and stroke in sub-saharan Africa

Worldwide variations How common is stroke in sub-saharan Africa (referred to as Africa in this article)? Do risk factors differ from those in developed countries? In the USA and the UK stroke mortality as well as prevalence and possibly incidence are higher in Black than in White nonulations (GILLUM, 1986. In Africa coronary heart d&ash (CHD) appears to be very rare, particularly in rural areas (SEEDAT, 1990), but in Black Afro-Americans in the USA CHD is common. For every 1000 people in the UK approximately 5 will have disability related to stroke (prevalence) and in one year 2 new strokes will occur (incidence). In recent decades death rates from stroke have fallen dramatically in most industrialized nations but it still remains the third commonest cause of death. Mortality within one month varies between 17 and 34% (average 24%), while annual mortality is about 42% (BONITA, 1992). Institutional care is required by about 20% of survivors but in Africa care for such patients would be provided within the immediate and extended family. Age-standardized mortality rates in people aged 40-69 years vary ten-fold between countries, but these differences are not fwed. For example, Japan has high rates of stroke and low rates of CHD whereas men of Japanese ancestry living in the USA have lower rates of stroke and higher rates of CHD (WHO, 1988). The variation in stroke mortality by place is greater than the variation in incidence. This in part may be explained by different types of stroke. Primary intracranial haemorrhage, which has a much worse prognosis than thrombotic stroke, is rather more common in Japan and possibly China than in western countries, There is less extracranial, but more intracranial, arterial disease in Japan compared with Caucasian populations (NISHIMARU et al., 1984) and this may also be true of Blacks (GIL-PERALTA et al., 1990). In the US, death rates for all cerebrovascular disease are 50% greater in Blacks than in Whites. Onlv Tanan has a higher<troke rate (209 per 100 000) than thai of Black Americans (165 per 100 000). The high rates in AfroCaribbeans in the UK are not entirely explained by their high levels of blood pressure (BONITA, 1992). In the USA hypertension is more common, more aggressive, and less well-managed in Blacks than in Whites even though, when they have equal access to treatment, hypertensive Blacks respond in a similar manner to, and experience a lower incidence of cardiovascular diseases than, Whites (KAPLAN, 1992). Average differences in blood pressure of slightly less than 5 mm Hg during the second decade increase to nearly 20 mm Hg during the sixth. Blacks tend to experience more cardiovascular and renal damage and show a reduction of the usual nocturnal fall in blood pressures.