Vitamin D and Incidence of Prediabetes or Type 2 Diabetes: A Four-Year Follow-Up Community-Based Study.

Aim: To examine whether the baseline 25-hydroxyvitamin D [25(OH)D] level was predictive of the onset of prediabetes or type 2 diabetes (T2DM) in the Chinese population.

Methods: This was a 4-year follow-up study that was conducted in the Chengdu region of China as part of the China National Diabetes and Metabolic Disorders Study. The study included 490 participants that were free of prediabetes and type 2 diabetes mellitus (T2DM) at baseline and had complete data by follow-up examinations. Glucose, insulin, and 25(OH)D levels were measured at baseline and at 4 years later. Prediabetes and T2DM were defined by results obtained from an oral glucose tolerance test.

Results: Over a 4-year follow-up, 95 (48.5‰) developed prediabetes and 31 (15.8‰) individuals developed diabetes. Low 25(OH)D status was significantly associated with the risk of developing prediabetes [OR 3.01 (95% CI: 1.50-6.06), P = 0.002] and T2DM [OR 5.61 (95% CI: 1.73-18.27), P = 0.004] after adjustment for multiple potential confounders. In a multiple linear regression analysis, low baseline levels of 25(OH)D were an independent predictor of increased insulin resistance over a 4-year period ( P < 0.05).

Conclusions: The current prospective study suggests that low 25(OH)D levels might have contributed to the incidence of prediabetes or T2DM in Chinese individuals. This trial is registered with TR-CCH-ChiCTR-OCS-09000361.