Objective: To evaluate the direct, indirect, and total prospective effects of serum concentrations of [25(OH)D, 25-hydroxycolecalciferol] on depressive symptoms in older adults.
Methods: Data from the second (2013-2015) and third (2017-2019) waves of the EpiFloripa Aging Cohort Study (≥ 60 years) were analyzed. Depressive symptoms were assessed by the 15-item Geriatric Depression Scale (GDS-15). 25(OH)D levels were measured using the microparticle chemiluminescence method. A directed acyclic graph (DAG) was constructed to identify the minimum set of adjustments. Structural equation modeling (SEM) analysis was used to determine the effects of 25(OH)D on depressive symptoms.
Results: A total of 574 older adults' data were analyzed (63.1% female). In the follow-up (n=390), 16.2% of older adults presented high-severity of depressive symptoms (> or = 6 points). SEM analysis revealed a small direct and negative effect of 25(OH)D (β=-0.11, P < 0.05), and a total negative effect (β=-0.13; P < 0.05) on depressive symptoms on wave 3 (an increase of 25(OH)D led to a decrease on depressive symptoms). No direct effect on wave 2 and no indirect effect mediated by depressive symptoms in wave 2 were found.
Conclusions: Findings indicate a prospective association between 25(OH)D and depressive symptoms, suggesting a long-term effect in older adults from southern Brazil.
Keywords: Vitamin D; aging; depression; longitudinal studies.