[Study on the relationship between serum vitamin D and the risk of type 2 diabetes in Harbin residents]

Objective: To analyze the relationship between serum vitamin D level and the risk of type 2 diabetes in Harbin residents. Methods: On April 2010, 24 communities in 7 districts of Harbin were selected as research sites using multi-stage stratified cluster random sampling method. A total of 9 734 residents aged 20-74 years was investigated using general questionnaire survey, dietary survey and biochemical indicators test and followed up from January 2015 to July 2016. A total of 4 721 subjects with serum vitamin D were included in the study. According to the quartile of baseline serum vitamin D, the subjects were divided into four groups, from Q1 to Q4 group. The multivariate logistic regression model was used to analyze the relationship between serum vitamin D and the risk of type 2 diabetes. A mediation analysis model was used to analyze the mediating role of insulin resistance in this risk relationship. Results: At the time of follow-up, 432 patients with type 2 diabetes were screened. The median (P(25), P(75)) age of the diabetic group and the non-diabetic group were 54 (49, 61) and 51 (43, 57) years, respectively, and males accounted for 40.5% (175 cases) and 35.5% (1 513 cases), respectively. The median (P(25), P(75)) serum vitamin D was 16.0 (13.5, 18.5) and 17.4 (14.3, 20.5) ng/ml, respectively. After relevant confounders and insulin resistance index (HOMA-IR) were adjusted, compared to the serum vitamin D level Q(1) group, the risk of diabetes was reduced by 40% in the Q(3) group with RR (95%CI) about 0.60 (0.44-0.82), while the risk of diabetes was reduced by 59% in Q(4) group with RR (95%CI) about 0.41 (0.29-0.57). Through mediation analysis, the Gutt index mediating effect representing peripheral insulin resistance was 53.8%, and the mediating effect of HOMA-IR representing hepatic insulin resistance was 6.6%. Conclusion: The risk of type 2 diabetes is low in Harbin residents with higher serum vitamin D level. Insulin resistance has a mediating effect on the relationship of vitamin D and the risk of type 2 diabetes.