Ethnic differences in retinal microvascular structure

Aims/hypothesis People of African origin have increased risk of stroke and retinal microvascular disease compared with populations of European origin. We compared quantitative measures of retinal microvasculature in British white Europeans and African Caribbeans. Methods Population-based study of 215 (45% male) British African-Caribbean migrants and 323 (48% male) white Europeans aged 40-69 years. Digitised retinal images were analysed using a validated semi-automated system. Results Arteriolar optimality deviation, an indicator of endothelial dysfunction, was greater in African Caribbeans (age- and sex-adjusted means [95% CIs]: 0.06 [0.05-0.06] vs 0.04 [0.04-0.05], p=0.004); this was unexplained by conventional risk factors. Arteriolar diameters were narrower in African Caribbeans (age- and sex-adjusted means [95% CIs]: 18.4 [18.1-18.6] vs 17.9 [17.6-18.2], p=0.011). These ethnic differences in diameters were attenuated on adjustment for systolic BP (SBP) (adjusted means: 18.2 vs 18.1, p=0.31). However, there was a significant interaction (p=0.011) between diabetes and SBP, such that SBP was strongly associated with arteriolar diameter in people without diabetes, but not in those with diabetes (adjusted beta-coefficients for SBP: Europeans: -0.42, p=0.002 vs 0.17, p=0.69, African Caribbeans: -0.35, p=0.023 vs 0.01, p=0.96). Other measures of retinal vasculature did not differ by ethnicity. Conclusions/interpretation British African Caribbeans appear to have poorer retinal arteriolar endothelial function than white Europeans. Higher BPs explained the narrower arterioles in African Caribbeans; however, patterns of association between arteriolar narrowing and BP suggest the possibility that cerebral autoregulation and/or remodelling might be adversely affected by diabetes in both ethnic groups.