Hypovitaminosis D is associated with sleep disorders in workers on alternating shifts with cardiovascular risk factors

Shift work has serious health impacts due to desynchronization of the circadian rhythm; consequently, the workers have increased sleep disturbances. Another impact is working hours, which can contribute to decreased sun exposure and lead to the development of hypovitaminosis D. Vitamin D has been implicated in extraskeletal functions in many physiological mechanisms, including sleep. Therefore, we aimed to verify the association between sleep parameters and hypovitaminosis D in shift workers with cardiovascular risk. We conducted a cross-sectional study of 82 male rotating shift workers (24-57 years old) with at least one cardiovascular risk factor (such as hyperglycemia, dyslipidemia, abdominal obesity, physical inactivity, hypertension, and smoking). Polysomnography was used to evaluate sleep parameters, while vitamin D levels were measured using a chemiluminescence method. Logistic regression was used to model the association between hypovitaminosis D and sleep parameters after adjustment for relevant covariates. Hypovitaminosis D (< 20 ng/mL) was seen in 30.5% of the workers. Shift workers with hypovitaminosis D had lower sleep efficiency, increased microarousal index, and lower arterial oxygen saturation after adjusting for seasonality, age, and body fat. Therefore, we suggest that hypovitaminosis D is associated with greater sleep disturbances in rotating shift workers with cardiovascular risk factors.