Association Between Shift Work and Vitamin D Levels in Brazilian Female Workers

Objectives: Vitamin D plays a crucial role in maintaining bone and muscle health and is associated with various health conditions. Risk factors for reduced vitamin D levels include occupation. The aim of this study was to explore the association between shift work and vitamin D levels among female workers. Methods: This cross-sectional study was conducted among 304 women from an industrial group located in southern Brazil. Vitamin D deficiency was defined as serum 25(OH)D levels < 20 ng/mL, and deficiency/insufficiency was defined as serum levels < 30 ng/mL. Work shift data were collected through interviews using the start and end times of work shifts, classified as "day shift" (6:00 AM ≤ hh:hh < 10:00 PM) and "night shift" (10:00 PM ≤ hh:hh < 6:00 AM), respectively. The association between vitamin D deficiency and shift work was expressed as prevalence ratio (PR), using Poisson regression adjusted for confounding variables. Results: The prevalence of vitamin D deficiency was 36.5% (95% CI: 31.1-41.9), while the prevalence of insufficiency was 75.7% (95% CI: 70.8-80.5). After adjustment, a significant association was found, with 65% and 17% higher probabilities of having vitamin D deficiency (PR = 1.65; 95% CI: 1.23-2.22; p = 0.001) and vitamin D deficiency/insufficiency (PR = 1.17; 95% CI: 1.02-1.35; p = 0.030) among nightshift workers compared with dayshift workers. Conclusions: The findings of this study indicate a high prevalence of hypovitaminosis D among Brazilian female fixed-shift workers as well as a higher probability of vitamin D deficiency and deficiency/insufficiency among nightshift workers compared with dayshift workers.