An international matched cohort study of the contribution of metabolic impairments to subclinical atherosclerosis in United Kingdom and Jamaican African-Caribbeans

Background A gradient of increased vascular risk exists across the African diaspora. We hypothesised that increased insulin resistance with environmental transition contributes to this risk. Methods The study was undertaken in 73 healthy African-Caribbeans in the UK and 151 age and sex matched African-Caribbeans in Jamaica. Body mass index (BMI), fasting insulin, insulin resistance, carotid intima media thickness (CIMT) and endothelium dependent vasodilatation (EDV) were compared. CIMT was measured ultrasonographically in the distal 1 cm of both common carotid arteries. EDV was measured the absolute change from baseline in the Reflection index (RI) of the digital volume pulse during intravenous infusion of albuterol (ΔRIALB). Results UK African-Caribbeans had greater CIMT (mean difference 0.124 [95% C.I. 0.075–0.173] mm, p < 0.0001) and decreased EDV (mean difference in ΔRIALB 5.1 [95% C.I. 2.5–7.6] percentage points, p < 0.0001). This was associated with higher insulin concentrations (mean difference 1.6 [95% C.I. 1.3–4.1] μU/mL, p = 0.038) and greater HOMA score (2.8 versus 2.0; p = 0.035) despite no significant differences in BMI (28.8 versus 27.6; p = 0.168) or the waist to hip ratio (0.86 versus 0.85; p = 0.188). HOMA scores correlated positively with CIMT (r = 0.35, p = 0.01) and negatively with ΔRIALB (r = −0.17; p = 0.02) in UK, but not in Jamaican, African-Caribbeans. A significant interaction was seen between HOMA and UK domicile for CIMT (p < 0.0001) and between fasting insulin and UK domicile for ΔRIALB (p < 0.0001). Conclusions Increased insulin resistance, associated with living in a nutritionally enriched environment, may contribute to early subclinical atherosclerosis in UK African-Caribbeans.