Meta-analytic evaluation of the association between head injury and risk of amyotrophic lateral sclerosis

AbstractHead injury is considered as a potential risk factor for amyotrophic lateral sclerosis (ALS). However, several recent studies have suggested that head injury is not a cause, but a consequence of latent ALS. We aimed to evaluate such a possibility of reverse causation with meta-analyses considering time lags between the incidence of head injuries and the occurrence of ALS. We searched Medline and Web of Science for case –control, cross-sectional, or cohort studies that quantitatively investigated the head-injury-related risk of ALS and were published until 1 December 2016. After selecting appropriate publications based on PRISMA statement, we performed random-effects meta-analyses to calculate odds ratios (ORs) a nd 95% confidence intervals (CI). Sixteen of 825 studies fulfilled the eligibility criteria. The association between head injuries and ALS was statistically significant when the meta-analysis included all the 16 studies (OR 1.45, 95% CI 1.21–1.74). However, in the meta-analyses considering the tim e lags between the experience of head injuries and diagnosis of ALS, the association was weaker (OR 1.21, 95% CI 1.01–1.46, time lag ≥ 1 year) or not significant (e.g. OR 1.16, 95% CI 0.84–1.59, time lag ≥ 3 years). Although it did not deny associations between head injuries and ALS, t he current study suggests a possibility that such a head-injury-oriented risk of ALS has been somewhat overestimated. For more accurate evaluation, it would be necess...
Source: European Journal of Epidemiology - Category: Epidemiology Source Type: research