Background: Head injury is associated with substantial morbidity and mortality. Long-term associations of head injury with dementia in community-based populations are less clear.
Method: 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 < 0.001, 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 = 0.008.
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.
