Vitamin D Status and Depressive Symptoms in Patients Undergoing Hemodialysis: A Cross-Sectional Study

Background/Objectives: Depressive symptoms are highly prevalent among patients undergoing maintenance hemodialysis. This study investigated the association between vitamin D status and depressive symptom burden in adults undergoing maintenance hemodialysis. Methods: This cross-sectional study included 91 patients treated at a university hospital in southern Brazil. Depressive symptoms were assessed using the Beck Depression Inventory-II (BDI-II), analyzed as a continuous outcome. Serum 25-hydroxyvitamin D [25(OH)D] was measured by chemiluminescence, and deficiency was defined as <20 ng/mL. Linear regression with HC3 robust standard errors was used, adjusting for age, sex, socioeconomic status, antidepressant or anxiolytic use, and vitamin D supplementation. Results: Serum 25(OH)D was available for 90 participants, of whom 19 (21.1%) were vitamin D deficient. Mean BDI-II scores were higher in deficient than non-deficient participants (18.4 ± 12.0 vs. 12.4 ± 9.0). Vitamin D deficiency was associated with a 6.00-point higher BDI-II score in the crude model (95% CI 0.07–11.94; p = 0.047) and a 5.05-point higher score after adjustment (95% CI 0.02–10.07; p = 0.049). In an extended model including sun exposure, hemodialysis duration, and social support, the estimated difference remained similar (β = 4.69; 95% CI −0.16–9.55; p = 0.058), although precision remained limited across the sensitivity analyses. The estimate was attenuated after adjustment for sleep quality, and no linear association was observed when 25(OH)D was modeled continuously. Conclusions: Vitamin D deficiency was associated with greater depressive symptom burden. However, the association was imprecise, attenuated after sleep adjustment, and absent when 25(OH)D was modeled continuously; causality cannot be established.