A 10-year observational study of the effects of serum 25OH vitamin D levels on the onset of prediabetes at a preventive medicine research center.

We report the findings of a 10-year study that followed the relationship between serum 25-hydroxyvitamin D (25OH vitamin D) levels and the onset of prediabetes, analyzed based on sex. One hundred eighty-seven participants were followed who had a baseline hemoglobin A1c (HbA1c) value below 6.0% and fasting plasma glucose level below 100 mg/dL. The cut-off values for vitamin D concentration were 27.7 ng/mL for men and 17.1 ng/mL for women, based on the receiver operating characteristic curve. The prediabetes incidence was significantly higher in women with a vitamin D concentration ≤17.1 ng/mL [HR = 7.08 (2.08-24.2), p = 0.002] than in men with a concentration ≤27.7 ng/mL [HR = 2.30 (0.63-8.35), p = 0.21], based on the cumulative incidence function curve. Multivariate analysis revealed that an abdominal circumference ≥90 cm and 25OH vitamin D concentration ≤17.1 ng/mL were independent, significant and intervenable risk factors for prediabetes in women. Low levels of vitamin D in women can be a predictive factor in the development of diabetes after 10 years.