Vitamin D serum concentration is prospectively associated with depressive symptoms in the EpiFloripa Aging Cohort Study: a structural equation modeling approach.

Objective: To evaluate the direct, indirect, and total prospective effects of serum concentrations of 25-hydroxycholecalciferol (25[OH]D) 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 with the 15-item Geriatric Depression Scale. 25(OH)D levels were measured using the microparticle chemiluminescence method. A directed acyclic graph was constructed to identify the minimum set of adjustments. Structural equation modeling analysis was used to determine the effects of 25(OH)D on depressive symptoms.

Results: Data from 574 older adults (63.1% female) were analyzed. In the follow-up (n=390), 16.2% of them presented severe depressive symptoms (= 6 points). Structural equation modeling analysis revealed that 25(OH)D had a small direct negative effect (ß = -0.11, p < 0.05) and an overall negative effect (ß = -0.13; p < 0.05) on depressive symptoms in wave 3 (increased 25[OH]D led to decreased depressive symptoms). No direct or indirect effect on depressive symptoms was found in wave 2.

Conclusion: Our findings indicate a prospective association between 25(OH)D and depressive symptoms, suggesting a long-term effect in older adults from southern Brazil.