Association between low serum 25-hydroxyvitamin D and depression in a large sample of Chinese patients with type 2 diabetes mellitus

Background: Because of the absence of data on the direct association between vitamin D and depression in patients with diabetes, we examined the association between vitamin D state (assessed by 25-hydroxyvitamin D [ 25(OH) D]) and the prevalence of depression in adult patients with type 2 diabetes mellitus(T2DM). Method: Cross-sectional data were obtained from 2786 patients with T2DM recruited from a Chinese diabetes registry. Patients' records were reviewed to obtain data pertaining to age, sex, Body Mass Index (BMI), marital status, level of education, smoking status, duration of diabetes mellitus, use of insulin, and presence of additional illnesses. A multiple logistic regression analysis adjusted for potential confounders was used to assess independent associations between serum levels of 25 (OH) D and depression (defined by the Patient Health Questionnaire-9). Results: Using the PHQ-9 cutoff value of >= 10, 5.71% (159/2786; 95% CI: 4.85-6.57%) were considered to have depression. The serum 25(OH) D levels were significantly lower in diabetic patients with depression than those patients without depression [10.2(IQR, 7.6-15.2) ng/ml vs. 14.6(IQR, 10.7-19.8)ng/ml, respectively; P < 0.0001]. Multivariate logistic regression analysis considering traditional risk factors and other biomarkers showed an inverse relationship between serum 25 (OH) D levels and depression when serum 25 (OH) D were used as a continuous variable (OR, 0.84; 95% CI, 0.77-0.90; P < 0.001). Compared with the first quartile of serum 25 (OH) D levels, the second quartile OR for depression was 0.83 (95% CI, 0.75-0.92, P=0.012). For the third and fourth quartiles, it was 0.40 (95% CI, 0.33-0.52, P < 0.001) and 0.15 (95% CI, 0.08-0.22; P < 0.001), respectively. Conclusions: We observed a significant negative association between serum levels of 25 (OH) D and depression in Chinese patients with T2DM.