Factors associated with relapses in relapsing-remitting multiple sclerosis: A systematic review and meta-analysis

BACKGROUND: The relapse is character of relapsing-remitting multiple sclerosis. The therapeutic goal is to reduce the risk of relapse. Factors associated with relapses can help to manage and prevent relapses. In addition, patients and doctors all pay attention to it. However, there are differences between studies. Our aim is to summarize factors associated with relapses in relapsing-remitting multiple sclerosis (RRMS). METHODS: PubMed, EMBASE, Web of science, Cochrane library, CNKI, Wanfang, SinoMed, and VIP were searched to identify risk factors about relapses in RRMS, which should be in cohort or case-control studies. This article was reported according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). The quality of studies was evaluated by the Newcastle-Ottawa Scale (NOS). Meta-analysis, subgroup and sensitivity analyses, and publication bias were all performed with Stata. This research has been registered on the international prospective register of systematic reviews (PROSPERO, CRD42019120502). RESULTS: 43 articles were included. Infection, postpartum period, risk gene, stress, and vitamin D were risk factors for relapses in RRMS. Pregnancy period was the protective factor. Among those, infection increased the risk of relapses in infection period (relative risk [RR], 2.07 [confidence interval (CI), 1.64 to 2.60]). Women in the postpartum period increased the risk of relapses compared with women before pregnancy (RR, 1.43 [CI, 1.19 to 1.72]), or women in pregnancy period (RR, 2.07 [CI, 1.49 to 2.88]). Women in the pregnancy period decreased the risk of relapses (RR, 0.56 [CI, 0.37 to 0.84]) compared with women before pregnancy. However, fewer studies, heterogeneity, and sample size were the limitations. CONCLUSION: It is reliable to adopt results about infection, pregnancy period, and postpartum period.