The following is a summary of “Associations Between Traumatic Brain Injury and Cognitive Decline Among Older Veteran Men – A Twin Study,” published in the September 2023 issue of Neurology by Chanti-Ketterl et al.
Traumatic brain injuries (TBI) are linked to dementia, but lifetime TBI’s impact on cognitive decline is unclear. Post-TBI cognitive interventions may delay dementia. Researchers performed a retrospective twin study to examine the association between lifetime TBI and cognitive decline.
They studied participants from the National Academy of Sciences National Research Council’s Twin Registry, consisting of male World War II veterans with reported TBI history. Data from up to four observations was collected over 12 years using the modified Telephone Interview for Cognitive Status (TICS-m). Linear random effects mixed models were applied to investigate the relationship between TBI and TICS-m in the entire sample and among co-twins with different TBI statuses. Additional TBI predictor variables encompassed the number of TBIs, severity (loss of consciousness [LOC]), and age at the first TBI (age <25 vs. 25+ [older age TBI])). These models were adjusted for age (centered at 70 years), age-squared, education, wave, twin pair, lifestyle behaviors, and medical conditions.
The results indicated 8,662 participants, 25% reported a history of TBI. Any TBI (β=-0.56, CI95% -0.73, -0.39), TBI with LOC (β=-0.51, CI95% -0.71, -0.31), and TBI at an older age (β=-0.66, CI95% -0.90, -0.42) were associated with lower TICS-m scores at age 70. TBI with LOC (β=-0.03, CI95% -0.05, -0.001), multiple TBIs (β=-0.05, CI95% -0.09, -0.002), and older age at TBI (β=-0.06, CI95% -0.09, -0.03) were linked to accelerated cognitive decline. In monozygotic pairs discordant for TBI (589 pairs), a history of any TBI (β=-0.55, CI95% -0.91, -0.19) and older age at TBI (β=-0.74, CI95% -1.22, -0.26) were associated with lower TICS-m scores at age 70. Those with multiple TBIs (β=-0.13, CI95% -0.23, -0.03) and older age at TBI (β=-0.07, CI95% -0.13, -0.002) demonstrated greater cognitive decline compared to their co-twin without TBI.
They concluded TBI is associated with poorer late-life cognitive outcomes, even in monozygotic twins.