Association of serum 25-hydroxyvitamin d concentrations with all-cause and cause-specific mortality among individuals with depression: A cohort study.

Background: Limited evidence exists on the relationship between vitamin D status and mortality in depressed patients.

Methods: This study investigates serum 25-hydroxyvitamin D [25(OH)D] concentrations in 8417 adults with depression among the National Health and Nutrition Examination Survey (NHANES, 2005-2018). Mortality outcomes were assessed through National Death Index records up to December 31, 2019. Cox proportional risk models estimated risk ratios (HR) and 95 % confidence intervals (CI) for all-cause, cardiovascular disease (CVD), and cancer mortality. Restricted cubic spline analyses explored the nonlinear association of serum 25(OH)D levels with mortality, using the likelihood ratio test for nonlinearity.

Results: The weighted mean serum 25(OH)D level was 66.40 nmol/L (95 % CI: 65.8, 67.0), with 36.3 % having deficient vitamin D (<50 nmol/L [20 ng/mL]). Over an average 7.16-year follow-up, 935 deaths were documented, including 296 CVD deaths and 191 cancer deaths. Higher serum 25(OH)D levels were associated with reduced all-cause mortality (HRs 0.55-1.00, p trend = 0.006) and cancer-specific mortality (HRs 0.36-1.00, p trend = 0.015) after multivariate adjustment. The relationship between serum 25(OH)D and all-cause mortality exhibited a nonlinear pattern (P for nonlinearity <0.001), with a 34 % lower risk for each unit increase in natural log-transformed 25(OH)D levels. Significant interactions were observed with age, antidepressant use, and diabetes status.

Conclusions: Higher serum 25(OH)D levels were associated with decreased all-cause and cancer-specific mortality in depressed adults, particularly among younger individuals and those using antidepressants or without diabetes. Further research is essential to understand mechanisms and interventions related to vitamin D in depression.