Vitamin D supplementation and activity of rheumatologic diseases: a systematic review and meta-analysis

Abstract

There is a historical background regarding the association between vitamin D and rheumatic diseases1,2. Based on this, many researchers began to investigate correlations between vitamin D serum levels and the presence/activity of rheumatic conditions1, as well as its known and novel biomolecular and cellular functions2,3, and clinical impact of vitamin D supplementation in many rheumatic diseases4,5. Despite great scientific curiosity around its possible therapeutic actions, many studies are merely observational6, and the few existent randomized clinical trials were never analyzed systematically. Therefore, the present study aims to provide a systematic review and, if feasible, a meta-analysis of such data, following the PRISMA (Preferred Reporting Items for Systematic reviews and Meta-Analyses)7,8 proposed methodology. Five databases will be explored (MEDLINE, EMBASE, LILACS, COCHRANE and CINAHL) in search of randomized trials, double blinded or not, that investigate clinical repercussions of vitamin D supplementation (or its analogues) for at least 3 months in immune-mediated rheumatic diseases. Standardized clinical and/or laboratorial outcomes related to disease activity will further be extracted from each article and analyzed according to each disease, as of before and after vitamin D supplementation. The results will be conveniently summarized in one or more tables in order to (1) systematically organize such data, (2) to assess individual and group bias, and (3) if possible, draw statistical conclusions, intending to identify rheumatic diseases in which vitamin D supplementation is an appropriate therapeutic strategy.