Serum 25-hydroxy vitamin D: a predictor of macrovascular and microvascular complications in patients with type 2 diabetes

Abstract

Objective People with diabetes frequently develop vascular disease. We investigated the relationship between blood 25-hydroxy vitamin D (25OH-D) concentration and vascular disease risk in type 2 diabetes. Research design and methods The relationships between blood 25OH-D concentration at baseline and the incidence of macrovascular (including myocardial infarction, stroke) and microvascular (retinopathy, nephropathy, neuropathy, and amputation) disease were analysed with Cox proportional-hazards models and logistic regression in an observational study of patients in the 5-year Fenofibrate Intervention and Event Lowering in Diabetes trial. Results 50% of the patients had low vitamin D concentrations, as indicated by median blood 25OH-D concentration of 49nmol/L. These patients with a blood 25OH-D concentration < 50nmol/L had a higher cumulative incidence of macrovascular and microvascular events than those with levels ≥ 50nmol/L. Multivariate analysis, stratified by treatment and adjusted for relevant confounders, identified blood 25OH-D concentration as an independent predictor of macrovascular events. A 50nmol/L difference in blood 25OH-D concentration was associated with a 23% (P=0.007) change in risk of macrovascular complications during the study and further adjustments for seasonality, hs-CRP and physical activity level had little impact. The unadjusted risk of microvascular complications was 18% (P=0.006) higher during the study, though the excess risk declined to 11-14% and lost significance with adjustment for HbA1C, seasonality or physical activity. Conclusions Low blood 25OH-D concentrations are associated with an increased risk of macrovascular and microvascular disease events in type 2 diabetes. However, a causal link remains to be demonstrated.