Genetics may not be enough to explain the rates of high blood pressure in US African-American populations, according to new research published today in BMC Medicine. The international study gives a different interpretation to the previous US data and suggests that high rates of hypertension might have more to do with lifestyle and socio-economic background than with racial origin.
Previous studies in the US, and to a lesser extent the UK, have shown that populations of African descent are much more likely to suffer from high blood pressure, and related conditions such as obesity and stroke, than white populations of European descent. This led to the assumption that individuals of African origin have a genetic predisposition to hypertension. However, this assumption was based solely on data collected in the US and had never been confirmed by international studies on other black populations.
Richard Cooper and his team, from Loyola University Strich School of Medicine in Illinois, compared standardised surveys of blood pressure from black populations in Nigeria, Jamaica and the US, and white populations from the US, Canada and 5 European countries. The study showed that there is a wide variation in the prevalence of hypertension within both racial groups when viewed internationally. In populations of African origin it ranges from 14% to 44%, while in white populations it goes from 27% to 55%.
Most importantly, the study revealed that black populations from Nigeria have a hypertension rate that is more than half the rate found in white Europeans and Americans. The results also show that incidence of high blood pressure seems to increase with the transition to an industrialized lifestyle: the total prevalence in Nigerian adults age 35 to 64 is 13.5%, while in Jamaicans it is 28.6% and in US blacks it is 44%.
"These data suggest that the impact of environmental factors among both populations may have been under-estimated" write the authors. They add that "the question of inherent susceptibility is probably non-testable under any circumstances" and argue that rather than trying to solve this question we should concentrate on identifying and preventing possible causes of hypertension, which are likely to be the same regardless of racial origin.