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

OBJECTIVE: People with diabetes frequently develop vascular disease. We investigated the relationship between blood 25-hydroxyvitamin 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 and stroke) and microvascular (retinopathy, nephropathy, neuropathy, and amputation) disease were analyzed 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: A total of 50% of the patients had low vitamin D concentrations, as indicated by median blood 25OH-D concentration of 49 nmol/L. These patients with a blood 25OH-D concentration <50 nmol/L had a higher cumulative incidence of macrovascular and microvascular events than those with levels ≥50 nmol/L. Multivariate analysis, stratified by treatment and adjusted for relevant confounders, identified blood 25OH-D concentration as an independent predictor of macrovascular events. A 50 nmol/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.