Relationship between vitamin D status and vascular complications in patients with type 2 diabetes mellitus. 
We aimed to investigate the association between serum 25-hydroxyvitamin D (25[OH]D) and microvascular complications in type 2 diabetes mellitus (T2DM) patients.  It was hypothesized that lower 25(OH)D would be associated with increased microvascular complications in T2DM.  A total of 257 T2DM patients (111 men, 146 women) who underwent diabetic microvascular complication (peripheral neuropathy, nephropathy, retinopathy) studies were recruited.  Patients were categorized into 3 groups according to vitamin D status: vitamin D sufficient (n = 41, 25[OH]D ≥ 20 ng/mL), vitamin D insufficient (n = 132, 10 ≤ 25[OH]D < 20 ng/mL), and vitamin D deficient (n = 84, 25[OH]D < 10 ng/mL).  In men, the prevalence of diabetic peripheral neuropathy (DPN) was significantly higher in patients with vitamin D deficiency than in those with insufficiency or sufficiency (38%, 11.7%, and 10%, respectively; P = .005).  In addition, the prevalence of diabetic nephropathy (DN) was significantly higher in women with vitamin D deficiency than in the other 2 groups (40%, 20.6%, and 0%; P = .007).  Compared with men in the vitamin D-sufficient group (reference), men in the vitamin D-deficient group had an increased risk of DPN after adjusting for confounding factors (odds ratio, 7.79; 95% confidence interval, 1.52-40.05).  For women, when the vitamin D-sufficient group was used as a reference, those in the vitamin D-deficient group had an increased risk of DN after adjusting for confounding factors (odds ratio, 4.27; 95% confidence interval, 1.58-11.56).  This present study found that a serum 25(OH)D level less than 10 ng/mL is independently associated with increased DPN in male patients and increased DN in female patients with T2DM.