Association of Serum Vitamin D Levels with Depression in Adults: A Nationwide Population-based Study in Korea

Abstract Background Vitamin D status may be associated with depression, but there have been inconsistencies in the reported estimates. This study aimed to examine the association of vitamin D status with depression in a large general population sample. Methods Cross-sectional data for a representative Korean sample of 1,825 people aged 19 years or older were obtained from the nationally representative Korean National Health and Nutrition Examination Survey (2014). Depression was defined by Patient Health Questionnaire-9 (PHQ-9) scores ≥10 (moderate/severe). Logistic regression was used to estimate the associations between depression and serum 25-hydroxyvitamin D [25(OH)D] levels. Continuous serum 25(OH)D level was categorized into quartiles. Continuous PHQ-9 scores were assessed using quantile regression. Adjustments for age, sex, marital status, level of education, lowest income quartile, body mass index, level of physical activity, chronic conditions, serum creatinine level, glomerular filtration rate, and history of depression were used in the statistical analyses. Estimates of prevalence and odds ratios (OR) with 95% confidence intervals (CI) were made. Sampling weights were utilized to account for survey design effects. Results Individuals in the lowest serum 25(OH)D quartile level had significantly higher prevalence of depression than in the upper three quartiles (8.3% vs. 5.1%; p=0.024). No association was observed between serum 25(OH)D level and depression after adjusting for potential covariates (OR 1.48, 95%CI 0.93, 2.35; p=0.097]. However, a stronger association was observed among male respondents, with an estimated OR of 2.54 (95% CI 1.17, 5.50; p=0.018). Additionally, in the quantile regression analysis, estimates from adjusted models remained significant (β = −0.056, p=0.002). Conclusion While our findings support the association between lower vitamin D status and depression in Korean adults, additional studies are needed to clarify this relationship.