Ankle-brachial index and incident diabetes mellitus: the atherosclerosis risk in communities (ARIC) study

Background: Individuals with peripheral artery disease (PAD) often have reduced physical activity, which may increase the future risk of diabetes mellitus. Although diabetes is a risk factor for PAD, whether low ankle-brachial index (ABI) predates diabetes has not been studied. Methods: We examined the association of ABI with incident diabetes using Cox proportional hazards models in the ARIC Study. ABI was measured in 12,247 black and white participants without prevalent diabetes at baseline (1987-1989). Incident diabetes cases were identified by blood glucose levels at three subsequent visits (1990-92, 1993-95, and 1996-98) or self-reported physician diagnosis or medication use at those visits or during annual phone interview afterward through 2011. Results: A total of 3305 participants developed diabetes during a median of 21 years of follow-up. Participants with low (<= 0.90) and borderline low (0.91-1.00) ABI had 30-40% higher risk of future diabetes as compared to those with ABI of 1.10-1.20 in the demographically adjusted model. The associations were attenuated after further adjustment for other potential confounders but remained significant for ABI 0.91-1.00 (HR = 1.17, 95% CI 1.04-1.31) and marginally significant for ABI <= 0.90 (HR = 1.19, 0.99-1.43). Although the association was largely consistent across subgroups, a stronger association was seen in participants without hypertension, those with normal fasting glucose, and those with a history of stroke compared to their counterparts. Conclusions: Low ABI was modestly but independently associated with increased risk of incident diabetes in the general population. Clinical attention should be paid to the glucose trajectory among people with low ABI but without diabetes.