[Association between plasma 25-hydroxyvitamin D level and depressive symptom in older adults aged 65 years and above in 18 longevity areas in China]

Objective: To understand the association between plasma 25-hydroxyvitamin D [25(OH)D] level and depressive symptom in older adults aged ≥65 years in 18 longevity areas in China. Methods: Based on cross-sectional data from the 2021 China Healthy Ageing and Biomarkers Cohort Study. The information about the demographic characteristics, lifestyles, cognitive function, and disease history of the older adults were collected through face-to-face interviews. Fasting venous blood samples were taken to measure plasma 25(OH)D level. The risk for depressive symptom was evaluated by using the Patient Health Questionnaire-9 (PHQ-9), with score ≥10 indicating positive result. Multivariable logistic regression, multiple linear regression, and restricted cubic spline models were used to evaluate the relationship of plasma 25(OH)D level with the risk for depressive symptom and PHQ-9 score. Results: A total of 4 882 participants were included, with the mean age of (83.79±11.23) years and women accounting for 55.1%, and the detection rate of depressive symptom was 6.7% (329/4 882). The study participants were stratified into three tertile groups (T₁-T₃) based on plasma 25(OH)D level. Multivariable logistic regression analysis revealed a significant inverse association between plasma 25(OH)D level and depressive symptom. Compared with the T₁ group, the T₃ group had significantly lower risk for depressive symptom (OR=0.678, 95%CI: 0.493-0.928, P=0.016). Multiple linear regression analysis showed that higher plasma 25(OH)D level was negatively associated with PHQ-9 score (T₂: β=-0.426, 95%CI: -0.701 - -0.151, P=0.002; T₃: β=-0.705, 95%CI: -0.983 - -0.428, P<0.001). Restricted cubic spline models indicated a monotonically decreasing dose-response relationship between plasma 25(OH)D level and risk for depressive symptom (P for linear=0.010). Conclusion: In older adults aged ≥65 years from 18 longevity areas in China, plasma 25(OH)D level was significantly associated with the risk for depressive symptom.