RESUMEN
BACKGROUND: To date, hemodialysis (HD) is the most common therapy for chronic kidney disease (CKD) patients. However, it causes different complications such as sleep disorders. Sleep regulation is connected to vitamin D; hence, its deficiency might influence the quality and duration of sleep. This study is aimed at evaluating the correlation of sleep quality and vitamin D levels in 80 HD patients. METHODS: This cross-sectional study was performed on 80 hemodialysis patients admitted to 29 Bahman hospitals in Tabriz, Iran. Before beginning of dialysis, serum 25 (OH) D levels were assessed among patients and the sleep patterns and sleep quality of patients were accurately calculated by the Pittsburgh sleep quality index (PSQI) standard questionnaire. RESULTS: Our results showed that 22 HD patients (27.5%) had severe sleep disorders. In addition, it was found that serum levels of vitamin D had significant correlation with sleep quality (r = -0.341, p = 0.002) in general, even after adjusting confounding factors such as calcium (Ca), phosphate (P), and parathyroid hormone (PTH) level. In poor sleepers (PSQI ≤ 5), a negative correlation was observed between the levels of vitamin D and PSQI score (r = -0.397, p = 0.004). PSQI scores in the normal range of PTH (r = -0.377, p = 0.006) and in >600 pg/ml of PTH (r = -0.675, p = 0.011) had a correlation with vitamin D levels. The level of vitamin D was the single independent predictor of sleep efficiency (ß coefficient = -0.386, p = 0.001). CONCLUSION: The present project reported that the positive effect of vitamin D is associated with sleep disorder in HD patients. In future studies, normal levels of Ca and P should be considered along with normal vitamin D levels among the included patients.