Exploring causal relationship of traumatic brain injury and comorbidities: A Mendelian randomization study

Previous observational studies demonstrated a link existed between traumatic brain injury (TBI) and cerebral disease and multisystem complications, such as dementia, pneumonia, and gastrointestinal disease, but they could be confused by confounding and reverse causality. We aimed to figure out the causal correlation between TBI and the following complications. Database concerning TBI and complications from genome-wide association study (GWAS) and two-sample Mendelian randomization (MR) analysis was employed to examine whether TBI was causally associated with the risk of some complications. All the analysis was carried out through R, version 4.3.3. MR analyses indicated that any dementia has a promotional effect on TBI (OR = 1.067, 95% CI, 1.011-1.123, p = 0.017). However, there was no causal genetically association between TBI and Alzheimer's disease (AD), Parkinson's disease (PD), pneumonia, or gastrointestinal disease. Contrary to observational studies, our results uncovered little causal association between TBI and PD, AD, depression, pneumonia, and gastrointestinal diseases. Interestingly, we found any dementia might be the risk of TBI, which was a new discovery.