Traumatic brain injury and cognitive change over 30 years among community-dwelling older adults

Abstract

INTRODUCTION: There is limited evidence regarding the rate of long-term cognitive decline after traumatic brain injury (TBI) among older adults. METHODS: In this prospective cohort study, time-varying TBI was defined by self-report and International Classification of Disease diagnostic codes. Cognitive testing was performed at five visits over 30 years and scores were combined into a global cognition factor score. Adjusted linear mixed-effects models estimated the association of TBI with cognitive change. RESULTS: A total of 11,701 Atherosclerosis Risk in Communities (ARIC) Study participants (mean baseline age 58 years, 58% female, 25% Black) without TBI at baseline were included. Over follow-up, 18% experienced TBI. The adjusted average decline in cognition per decade (standard deviation units) was more than twice as fast among individuals with ≥ 2 incident TBIs (β = –0.158, 95% confidence interval [CI] = –0.253,–0.063), but not among individuals with 1 TBI (β = –0.052, 95% CI = –0.107, 0.002), compared to without TBI (β = –0.057, 95% CI = –0.095, –0.020). DISCUSSION: This study provides robust evidence that TBIs fundamentally alter the trajectories of cognitive decline. Highlights: The adjusted average decline in cognition per decade (standard deviation units) was more than twice as fast among individuals with ≥ 2 incident traumatic brain injuries (TBIs; β = –0.158, 95% confidence interval [CI] = –0.253, –0.063), but not with 1 TBI (β = –0.052, 95% CI = –0.107, 0.002), compared to without TBI (β = –0.057, 95% CI = –0.095, –0.020). Over a period of 30 years, this difference in cognitive decline is equivalent to individuals with ≥ 2 TBIs being 9.7 years older at baseline. Associations of TBI were stronger among individuals with one or two apolipoprotein E (APOE) ε4 alleles than among individuals with zero APOE ε4 alleles (P interaction = 0.007).