Hypovitaminosis D in Patients with Type 2 Diabetes Mellitus: A Relation to Disease Control and Complications

Aims. This study aims at assessing the relationship between 25 (OH) vitamin D (25-OHD) levels and microvascular complications in patients with type 2 diabetes mellitus (DM2). Methods. 136 patients (59 ± 11 years) with DM2 (disease duration 8.6 ± 7 years) participated in this cross-sectional study. Anthropometric data, HbA1c, 25-OHD levels, serum creatinine, and urine microalbumin/creatinine ratio were collected. Dilated retinal exam was performed, and diabetic neuropathy was assessed using the United Kingdom Screening Score. Results. Serum 25-OHD correlated negatively with HbA1c (r = -0.20,  P = 0.049). Mean 25-OHD levels were lower in subjects with diabetic retinopathy compared to those without retinopathy (12.3 ± 5.5 versus 21.8 ± 13.7, P < 0.001) and lower in subjects with diabetic neuropathy compared to those without neuropathy (16.4 ± 10.4 versus 23.5 ± 14.5, P = 0.004). After adjustment for BMI, diabetes duration, and smoking, 25-OHD was an independent predictor of HbA1c ( β   -0.14; P = 0.03). After adjustment for HbA1c, age, smoking, BMI and disease duration, 25-OHD were independent predictors for diabetic retinopathy: OR 2.8 [95% CI 2.1-8.0] and neuropathy: OR 4.5 [95% CI 1.6-12] for vitamin D < 20 versus vitamin D ≥ 20 ng/mL. Conclusion. Low serum 25-OHD level was an independent predictor of HbA1c, diabetic neuropathy, and diabetic retinopathy in patients with DM2.