title: Ethnic differences in retinal microvascular structure.
abstract: OBJECTIVE
  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
  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.
authors.affiliation: International Centre for Circulatory Health, Imperial College London, 59 North Wharf Road, London W2 1LA, UK. t.tillin@imperial.ac.uk
authors.forename: T
authors.initials: T
authors.lastname: Tillin
authors.forename: R M
authors.initials: RM
authors.lastname: Evans
authors.forename: N W
authors.initials: NW
authors.lastname: Witt
authors.forename: P S
authors.initials: PS
authors.lastname: Sharp
authors.forename: P M
authors.initials: PM
authors.lastname: McKeigue
authors.forename: N
authors.initials: N
authors.lastname: Chaturvedi
authors.forename: A D
authors.initials: AD
authors.lastname: Hughes
mesh_terms: D001331:Automation; D044383:Black People; D001794:Blood Pressure; D017691:Caribbean Region; D005006:Ethnicity; D005060:Europe; D005260:Female; D005451:Fluorescein Angiography; D006801:Humans; D015994:Incidence; D008297:Male; D008833:Microcirculation; D008875:Middle Aged; D012164:Retinal Diseases / Q000453:epidemiology; D012171:Retinal Vessels / Q000033:anatomy & histology*; D044465:White People