Head injury and 25-year risk of dementia

Introduction: Head injury is associated with significant morbidity and mortality. Long-term associations of head injury with dementia in community-based populations are less clear. Methods: Prospective cohort study of 14,376 participants (mean age 54 years at baseline, 56% female, 27% Black, 24% with head injury) enrolled in the Atherosclerosis Risk in Communities (ARIC) Study. Head injury was defined using self-report and International Classification of Diseases, Ninth/Tenth Revision (ICD-9/10) codes. Dementia was defined using cognitive assessments, informant interviews, and ICD-9/10 and death certificate codes. Results: Head injury was associated with risk of dementia (hazard ratio [HR] = 1.44, 95% confidence interval [CI] = 1.3-1.57), with evidence of dose-response (1 head injury: HR = 1.25, 95% CI = 1.13-1.39, 2+ head injuries: HR = 2.14, 95% CI = 1.86-2.46). There was evidence for stronger associations among female participants (HR = 1.69, 95% CI = 1.51-1.90) versus male participants (HR = 1.15, 95% CI = 1.00-1.32), P-for-interaction <.001, and among White participants (HR = 1.55, 95% CI = 1.40-1.72) versus Black participants (HR = 1.22, 95% CI = 1.02-1.45), P-for-interaction =.008. Discussion: In this community-based cohort with 25-year follow-up, head injury was associated with increased dementia risk in a dose-dependent manner, with stronger associations among female participants and White participants.