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.