The Association of Sleep Quality and Vitamin D Levels in Hemodialysis Patients

Abstract

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 ( $\text{PSQI}\le 5$ ), 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 ( $\beta \text{coefficient}=-0.386$ , $p=0.001$ ). 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.