History of head trauma and the risk of multiple sclerosis: A systematic review and meta-analysis.

Background: Multiple sclerosis (MS) is a chronic disease of the central nervous system with unclear etiology involving genetic, environmental, and immunological factors. The potential link between head trauma and MS is controversial, with conflicting evidence. This systematic review and meta-analysis aim to assess the risk of developing MS following head trauma.

Methods: A systematic search of electronic databases was conducted, including studies that investigated the risk of MS in individuals with a history of head trauma compared to those without. Observational studies, including cohort and case-control designs, were included. Data synthesis was conducted using RevMan software. GRADE was used to assess the certainty of evidence.

Results: Fifteen studies comprising 1,619,640 participants were included in the meta-analysis. The overall odds of developing MS were significantly higher in the head trauma group compared to the control group (OR = 1.41;95 % CI = [1.23, 1.61]; P < 0.00001; I = 62 %). Sensitivity analyses based on the number of participants and quality further supported our results. Subgroup analysis showed that results remained consistent across different head trauma identification methods (P = 0.92), early age head trauma and head trauma defined as TBI, or concussion were also significant predictors of MS (P < 0.0001). Analysis of the number of hits suggested a dose-response relationship between the number of head injuries and the risk of MS. According to the GRADE, all outcomes were classified as low or very low certainty of the evidence.

Conclusion: This meta-analysis suggests that a history of head trauma may be associated with an increased risk of developing MS. Further research is warranted to support our findings and explore the mechanisms linking head trauma to MS.