A meta-analysis: Does vitamin D play a promising role in sleep disorders?
Yan S, Tian Z, Zhao H, Wang C, Pan Y, Yao N, Guo Y, Wang H, Li B, Cui W (2020) Food Sci Nutr 8(10) 5696-5709. doi: 10.1002/fsn3.1867. eCollection 2020 Oct.
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Abstract:
Background:
Sleep disorders, one of the most common problems in the general population, have been related to a series of harmful health consequences. Vitamin D appears to be associated with sleep disorders. However, the difference in vitamin D levels between sleep disorder subjects and people without a sleep disorder is unclear. Simultaneously, the influence of vitamin D replenishment on sleep disorders remains controversial.
Methods:
PubMed, MEDLINE, Web of Science, and Cochrane Library were searched for literatures published until October 2019. Using a random effects model, a meta-analysis was conducted to calculate the standard mean difference to evaluate the difference in vitamin D concentrations between sleep disorder subjects and normal people and the efficacy of vitamin D supplementation on sleep disorders.
Results:
Our study found that the serum vitamin D levels in the sleep disorder subjects were lower than that in the normal people (SMD = -0.75 ng/ml, 95% CI = -0.93, -0.57 ng/ml). Moreover, the Pittsburgh Sleep Quality Index (PSQI)in the subjects with vitamin D supplementation was lower than that in the controls (SMD = -0.45, 95% CI = -0.76, -0.13).
Conclusions:
Vitamin D could play a promising role in sleep disorders. More data are required to confirm the efficacy of vitamin D supplementation for improving sleep disorders.
FAB RESEARCH COMMENT:
Both sleep problems and Vitamin D deficiencies or insufficiencies are widespread in the general population - and both are associated with higher risks for almost all developmental and mental health conditions.This new review examined the current evidence for links between Vitamin D status and sleep problems, conducting separate meta-analyses for (1) studies assessing associations between Vitamin D status (as assessed by serum levels) and sleep, and (2) clinical treatment trials of supplementation with Vitamin D.
Results showed that:
- individuals with low Vitamin D status show significantly more sleep problems
- preliminary clinical trial evidence also suggests that Vitamin D supplementation may help to improve sleep - but such trials are still few in number, so more large-scale, high quality trials are still needed
In addition to sleep problems, experimental, clinical and epidemiological evidence also implicates low Vitamin D status in most of the chronic, non-communicable diseases associated with modern diets and lifestyles - including obesity and diabetes, immune disorders.
However, clinical trials of Vitamin D supplementation often show mixed or negative results - even for physical health problems that are known to be caused or exacerbated by Vitamin D deficiency (such as osteoporosis, or impaired immunity).
As many researchers have flagged, randomised, double-blind, placebo-controlled clinical trials (RCT) of Vitamin D supplementation are subject to numerous methodological complications. Some of these are common to nutritional interventions in general, while others arise from known genetic individual differences in response to Vitamin D; and the extraorindary complexity of Vitamin D's actions and synergies with other nutrients - such as calcium, magnesium and Vitamin K2.
For these reasons, the relative 'absence of evidence' from RCTs of Vitamin D supplementation cannot be taken as 'evidence of absence'.
And in this study - the fact that the small number of RCTs published to date appears to show benefits from Vitamin D supplementation for sleep problems is encouraging, albeit preliminary, evidence.
For more information on the links between nutrition and sleep, see:
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