Prevalence of vitamin D deficiency across the spectrum of glucose intolerance

BACKGROUND: Vitamin D deficiency (VDD) is inversely associated with insulin resistance. We studied the prevalence of VDD across the spectrum of glucose intolerance, including normal glucose tolerance (NGT), prediabetes (PD) and type 2 diabetes (T2D). METHODS: We conducted this cross-sectional, observational study by serially including the PD and T2D patients seen between June and December 2014. We excluded patients with major illness, secondary diabetes and use of vitamin D or glucocorticoids. VDD was defined as serum 25-hydroxy vitamin D (25OHD) less than 30 ng/mL. The study population was divided into 3 groups: T2D (Group 1; n = 274), PD (Group 2; n = 62) and NGT controls (Group 3; n = 270) for the analysis and appropriate statistical methods were used. RESULTS: The study participants (n = 606, 28 % males) had a mean age of 43.2 ± 13.6 years, BMI of 27.7 ± 5.9 kg/m(2), HbA1c of 6.6 ± 2 % and mean 25OHD of 18.8 ± 15.7 ng/mL. VDD was seen in 85 % of the entire study population including 84 % in T2D, 77 % in prediabetes and in 87 % of the controls. The mean 25OHD levels were lower in the control group (16.8 ng/mL) when compared with T2D and prediabetes (19.9 and 22.4 ng/mL) respectively (P = 0.0124). Univariate analysis showed higher odds of VDD in females (P < 0.0001) but no association with diabetes, age, BMI and HbA1c. CONCLUSION: Our data showed that VDD is prevalent in the majority of the population, irrespective of the underlying glucose intolerance. Further studies are required to determine the association between the vitamin D and diabetes.