Resting and ambulatory blood pressure differences in Afro-Caribbeans and Europeans.

To investigate why mortality from stroke in people of Afro-Caribbean origin is twice the average for England and Wales, we examined 1166 European and Afro-Caribbean people in London. Age-standardized median systolic blood pressure was 6 mm Hg higher (128 versus 122 mm Hg) in Afro-Caribbean than European men and 17 mm Hg higher (135 versus 118 mm Hg) in Afro-Caribbean than European women. Migrants from West Africa and the Caribbean had similar blood pressures. Body mass index was higher in Afro-Caribbean than European women, accounting for 4 mm Hg of the systolic difference. Diabetes prevalence was 16% in Afro-Caribbeans and 5% in Europeans (P < .001), accounting for 1 mm Hg of the difference in systolic pressure in men and 2 mm Hg in women. In participants not taking antihypertensive medication, mean fall in ambulatory systolic pressure between daytime and nighttime, adjusted for resting blood pressures, was 24 mm Hg in Europeans and 18 mm Hg in Afro-Caribbeans (P = .05), and percent day-night fall in systolic blood pressure adjusted for resting systolic pressure was 17% in Europeans and 12% in Afro-Caribbeans (P < .05). This difference persisted when men and women and normotensive and hypertensive individuals were examined separately. We estimate that the differences in blood pressure between Afro-Caribbeans and Europeans may be enough to account for ethnic differences in stroke mortality in women but not men. The reasons for the high prevalence of hypertension and related morbidity in this and other populations of African descent remain to be established.