Objectives: A gradient of increased vascular risk with migration exists across the African diaspora. We investigated the hypothesis that differences in homocysteine/folic acid status contribute to this increased risk.
Design: Community cohort study of 73 Afro-Caribbeans in the United Kingdom and 151 matched Afro-Caribbeans in Jamaica with no conventional vascular risk factors.
Methods: Subjects were compared for baseline characteristics, vascular risk profile, homocysteine (tHcy), folate and B12 concentrations. Endothelium-dependent vasodilatation was assessed by measuring the absolute change from baseline in the reflection index (RI) of the digital volume pulse during intravenous infusion of albuterol (5 μg/min, ΔRIALB) and glyceryltrinitrate (GTN) (5 μg/min, ΔRIGTN). Carotid intima media thickness (CIMT) was measured ultrasonographically in the distal 1 cm of the common carotid artery.
Results: UK Afro-Caribbeans had higher tHcy (mean difference 2.3 (95% confidence interval 1.3 to 3.4) μmol/l) and lower folate (mean difference 3.2 (95% CI 1.8 to 4.7) μg/l) levels. ΔRIALB was 5.1 (95% CI 2.5 to 7.6) percentage points lower and CIMT 0.124 (95% CI 0.075 to 0.173) mm greater in UK Afro-Caribbeans. Higher tHcy and lower folate concentrations correlated with impaired ΔRIALB and increased CIMT. A 1 μg/l increase in folate concentration was associated with 0.3 (95% CI 0.1 to 0.5) percentage point increase in ΔRIALB and 0.002 (95% CI 0.001 to 0.006) mm decrease in CIMT, independent of blood pressure, smoking and vascular risk profile.
Conclusions: Lower folate concentrations in UK compared with West Indian African-Caribbeans may contribute to the higher stroke risk seen in UK African-Caribbean people.
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LK had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis. He will take responsibility for the integrity of the work as a whole, from inception to published article.
Funding: This research was supported by a project grant from the Wellcome Trust (GR061574FR). AMS is supported by the British Heart Foundation.
Competing interests: PC is an adviser to Micro Medical, the company that provided the pulse wave analysis instrument. The authors have no other conflicting interests or other disclosures to make in connection with this research.