This study aims to examine whether low serum 25-hydroxyvitamin D [25(OH)D] concentrations are correlated with increased risk of incident type 2 diabetes (T2D) in a Chinese population. The present prospective cohort study included 5,543 participants aged 40-75 y old and is free of diabetes at baseline in Lanzhou city, China. Serum 25(OH)D concentrations were measured. T2D incidence was defined based on obtained results from oral glucose tolerance tests or a self-reported previous diagnosis of diabetes by healthcare professionals. The association between baseline serum 25(OH)D concentrations and incident T2D was investigated using Cox proportional hazards model and restricted cubic spline. Of 5,543 participants (1,433 men and 4,110 women) followed for an average period of 3.9 y, 239 (4.3%) developed diabetes. No significant difference in serum 25(OH)D concentrations was found between individuals who developed diabetes and those who did not (p>0.05). Furthermore, serum 25(OH)D quartiles were not associated with T2D incidence (HR 1.33, 95% CI: 0.89-1.97, p=0.18) after adjusting for body mass index (BMI) and other potential confounders, as well as in subgroups classified with sex (men, women), glucose status (normal glucose tolerance, prediabetes), and BMI (<25 kg/m2, ≥25 kg/m2). The lower serum 25(OH)D concentrations are not associated to a higher risk of incident T2D in the present Chinese cohort after adjusting for BMI and other numerous potential confounding factors.
Keywords: 25-hydroxyvitamin D; association; cohort study; type 2 diabetes; vitamin D.