Is traumatic brain injury a risk factor for neurodegeneration? A meta-analysis of population-based studies

Background: To determine the association of prior traumatic brain injury (TBI) with subsequent diagnosis of neurodegeneration disease. Methods: All studies from 1980 to 2016 reporting TBI as a risk factor for diagnoses of interest were identified by searching PubMed, Embase, study references, and review articles. The data and study design were assessed by 2 investigators independently. A meta-analysis was performed by RevMan 5.3. Results: There were 18 studies comprising 3,263,207 patients. Meta-analysis revealed a significant association of prior TBI with subsequent dementia. The pooled odds ratio (OR) for TBI on development of dementia, FTD and TDP-43 associated disease were 1.93 (95% CI 1.47-2.55, p < 0.001), 4.44 (95% CI 3.86-5.10, p < 0.001), and 2.97 (95% CI 1.35-6.53, p < 0.001). However, analyses of individual diagnoses found no evidence that the risk of Alzheimer's disease, and Parkinson's disease in individuals with previous TBI compared to those without TBI. Conclusions: History of TBI is not associated with the development of subsequent neurodegeneration disease. Care must be taken in extrapolating from these results because no suitable criteria define post TBI neurodegenerative processes. Therefore, further research in this area is needed to confirm these questions and uncover the link between TBI and neurodegeneration disease.