Estimation of the risk of stroke in black populations in Barbados and South London.

BACKGROUND AND PURPOSE The incidence of stroke in black populations is a public health issue, but how risk varies between black communities is unclear. METHODS Population-based registers in South London (SLSR) and Barbados (Barbados Register of Strokes [BROS]). Stroke incidence estimated by age group, gender and stroke subtype from January 1995 to December 2002 (SLSR), and October 2001 to September 2003 (BROS). Incidence rate ratios [IRR] estimated adjusting for age and sex. RESULTS Two hundred and seventy-one cases registered in SLSR and 628 cases in BROS. Average age of stroke was 66.1 years (SD 13.7) in SLSR and 71.5 years (SD 14.9) in BROS (P<0.001). The incidence rate/1000 population in SLSR was 1.61 (European adjusted; 95% CI, 1.41 to 1.81) and 1.08 (world adjusted; 95% CI, 0.95 to 1.21). For Barbados incidence rates were 1.29 (European adjusted; 95% CI, 1.19 to1.39) and 0.85 (world adjusted; 95% CI, 0.78 to 0.92). Overall IRR for SLSR: BROS adjusted for age and sex was 1.26 (95% CI, 1.09 to 1.46). Statistically significant subtype differences included total anterior cerebral infarction (IRR, 1.82; 95% CI, 1.23 to 2.69), posterior cerebral infarction (IRR, 2.12; 95% CI, 1.28 to 3.53), primary intracerebral hemorrhage (IRR, 1.56; 95% CI, 1.03 to 2.35) and subarachnoid hemorrhage (IRR, 5.04; 95% CI, 2.54 to 9.97). CONCLUSIONS The risk of stroke in black Caribbeans is higher in South London than Barbados, and particularly so for specific stroke subtypes. The risk in Barbados approaches that in the white population in South London and strokes occur at an older age. Whether environmental factors mediate these differences in migrant populations requires further study.