Sex, race, and risk of dementia diagnosis after traumatic brain injury among older veterans

Objective To investigate whether sex and race differences exist in dementia diagnosis risk associated with traumatic brain injury (TBI) among older veterans. Methods Using Fine-Gray regression models, we investigated incident dementia diagnosis risk with TBI exposure by sex and race. Results After the exclusion of baseline prevalent dementia, the final sample (all veterans >= 55 years of age diagnosed with TBI during the 2001-2015 study period and a random sample of all veterans receiving Veterans Health Administration care) included nearly 1 million veterans (4.3% female; 81.8% White, 11.5% Black, and 1.25% Hispanic), 96,178 with TBI and 903,462 without TBI. Compared to those without TBI, Hispanic veterans with TBI were almost 2 times more likely (17.0% vs 10.3%; hazard ratio [HR] 1.74, 95% confidence interval [CI] 1.51-2.01), Black veterans with TBI were >2 times more likely (11.2% vs 6.4%; HR 2.15, 95% CI 2.02-2.30), and White veterans with TBI were nearly 3 times more likely to receive a dementia diagnosis (12.0% vs 5.9%; HR 2.71, 95% CI 2.64-2.77). A significant interaction between TBI and race for dementia diagnosis was observed (p< 0.001). Both male and female veterans with TBI were more than twice as likely (men 11.8% vs 5.9%, HR 2.60, 95% CI 2.54-2.66; women 6.3% vs 3.1%, HR 2.36, 95% CI 2.08-2.69) to receive a diagnosis of dementia compared to those without. There was a significant interaction effect between sex and TBI (p= 0.02), but the magnitude of differences was small. Conclusions In this large, nationwide cohort of older veterans, all race groups with TBI had increased risk of dementia diagnosis, but there was an interaction effect such that White veterans were at greatest risk for dementia after TBI. Further research is needed to understand the mechanisms for this discrepancy. Differences in dementia diagnosis risk for men and women after TBI were significant but small, and male and female veterans had similarly high risks of dementia diagnosis after TBI.