Vitamin D status and tic disorder: a systematic review and meta-analysis of observational studies.

Objective: Tic disorders (TD) are a common neurodevelopmental disorder, it can be divided into transient tic disorder (TTD), chronic motor or vocal tic disorder (CTD), and Tourette syndrome (TS). Our research is to evaluate the clinical relationship between tic disorders and vitamin D level in children. Methods: Online databases, including CNKI, Wanfang, VIP, Cochrane Library, PubMed and Embase digital knowledge service platform, were checked up to June 2022 for relevant observational studies published in Chinese and English. A random-effects model was incorporated to summarize the study results. The RevMan5.3 software was used for meta-analysis. Results: Out of 132 retrieved articles, 13 observational studies were eligible for inclusion in the systematic review and meta-analysis, comparing serum Vitamin D levels between children with TD and HC (healthy controls), including different subtypes of TD (TTD, CTD and TS). The results showed that the serum vitamin D levels in the TD group were lower than those in the HC group (MD = -6.64, 95% CI: -9.36 to -3.93, Conclusions: Our meta-analysis showed that the vitamin D level of children with TD was lower than that of healthy children. However, there was no difference between the subgroup. Due to the limitations of included studies in research design and diagnostic criteria, large samples, multi-center and high-quality studies are still needed for further analysis and confirmation.