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Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
Forest plot for meta-analysis on the association between vitamin D and sleep disorders risk. Data showed low vs. high levels of serum vitamin D, using a fixed-effects model. ID: identification; ES: effect size.