Abstract
Epidemiology studies have investigated the association between vitamin D and the risk of sleep disorders, but the results remain controversial. Therefore, we conducted this meta-analysis with the goal of clarifying the association between vitamin D and sleep disorders risk. All relevant studies were searched using PubMed, EMBASE, and Web of Science from inception to January 2018. Pooled odds ratios (ORs) and 95% confidence interval (CIs) were calculated using a fixed-effect model A total of nine studies (6 cross-sectional, 2 case-control, and 1 cohort studies) involving 9397 participants were included. By comparing the lowest verse highest levels of serum vitamin D, we found that participants with vitamin D deficiency (VDD) had a significantly increased risk of sleep disorders (OR: 1.50, 95% CI: 1.31, 1.72). Subgroup analysis showed that VDD also was associated with poor sleep quality (OR: 1.59, 95% CI: 1.23, 2.05), short sleep duration (OR: 1.74, 95% CI: 1.30, 2.32), and sleepiness (OR: 1.36, 95% CI: 1.12, 1.65). Subgroup analyses further indicated that serum 25(OH)D <20 ng/mL could significantly increase the risk of unhealthy sleep. This meta-analysis suggest that vitamin D deficiency is associated with a higher risk of sleep disorders. More high-quality cohort studies and randomized controlled trials (RCTs) are needed to verify this association.
Highlights
Sleep, which accounts for one-third part of the lifetime, is of the great essence in our daily routine [1]
We carried out a systematic literature search from inception to the January 2018 in three databases (PubMed, EMBASE, and Web of Science) to identify relevant available articles reporting the relationship between vitamin D and sleep disorders
Literature Search and Study Characteristics. For this meta-analysis, we searched a total of 2298 articles, after removing duplicates (n = 503), 1690 articles were excluded after reviewing the titles and abstract
Summary
Sleep, which accounts for one-third part of the lifetime, is of the great essence in our daily routine [1]. Healthy sleep is necessary for maintaining physical and psychological health. The daily sleep-wake cycle is controlled by circadian clock, different neurons, and hormones produced by the hypothalamus and environmental signals (dark/light) [3,4]. Sleep disorders have become an epidemic throughout the world [5,6,7,8], while many people, even medical staff, are not aware of their significance. Previous studies revealed that excessive sleep or sleep deprivation were associated with increased risk of adverse health events, including type II diabetes, hypertension, cancers, and all-cause mortality [9,10,11]
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