Abstract: Objective To investigate the correlation of baseline serum 25(OH) D level with the risk of type 2 diabetes mellitus (T2DM) and blood glucose control in diabetic patients among the middle-aged and elderly individuals in Chengguan District of Lanzhou, Gansu Province. Methods Residents aged 40 to 75 years in Lanzhou were selected from the "REACTION" study conducted in 2011 and had been followed up since 2014. A total of 5044 subjects with complete data from the two surveys were analyzed. Participants were divided into Q1, Q2, Q3, and Q4 subgroups based on quartiles of serum 25(OH)D level for comparison of the incidence of T2DM and blood glucose control. Results Baseline 25(OH)D level was not found to correlate with FPG, 2h-PG or HbA1c levels among the residents (P>0.05). The participants were followed up for a mean of 3.4±0.6 years, and compared with those in Q1 group, the participants in Q2, Q3 and Q4 groups did not show significantly lowered risk of prediabetes or diabetes regardless of glucose tolerance status. Among the patients with T2DM, the compliance rate of glycemic control after the follow-up was significantly higher than that before the follow-up (63.4% vs 60.6%), and the levels of HbA1c, FPG, and 2h-PG decreased obviously after the follow-up. But compared with Q1 group, Q2, Q3 and Q4 groups showed no significant changes in glycemic control compliance rate or levels of HbA1c, FPG and 2h-PG after the follow-up (P>0.05). Conclusion There is no evidence that baseline 25(OH)D levels are associated with the risk of diabetes and blood glucose control in patients with T2DM.

Key words: 25-hydroxyvitamin D; normal glucose tolerance; prediabetes; type 2 diabetes mellitus; prospective cohort study