Traumatic brain injury and dementia risk in male veteran older twins-Controlling for genetic and early life non-genetic factors

Introduction This study leveraged the twin study design, which controls for shared genetic and early life exposures, to investigate the association between traumatic brain injury (TBI) and dementia. Methods Members of the National Academy of Sciences-National Research Council's Twins Registry of World War II male veterans were assigned a cognitive outcome based on a multi-step assessment protocol. History of TBI was obtained via interviews. Results Among 8302 individuals, risk of non-Alzheimer's disease (non-AD) dementia was higher in those with TBI (hazard ratio [HR] = 2.00, 95% confidence interval [CI], 0.97-4.12), than for AD (HR = 1.23, 95% CI, 0.76-2.00). To add more control of genetic and shared environmental factors, we analyzed 100 twin pairs discordant for both TBI and dementia onset, and found TBI-associated risk for non-AD dementia increased further (McNemar odds ratio = 2.70; 95% CI, 1.27-6.25). Discussion These findings suggest that non-AD mechanisms may underlie the association between TBI and dementia, potentially providing insight into inconsistent results from prior studies.

Automated summary

This study investigated the association between traumatic brain injury (TBI) and dementia using the twin study design. The results suggest that individuals with TBI have a higher risk of non-Alzheimer's disease (non-AD) dementia. Further analysis of twin pairs discordant for both TBI and dementia onset revealed that the association between TBI and non-AD dementia may be related to non-AD mechanisms.