Head Injury and Long-term Mortality Risk in Community-Dwelling Adults

Abstract

Importance: Head injury is associated with significant short-term morbidity and mortality. Research regarding the implications of head injury for long-term survival in community-dwelling adults remains limited.

Objective: To evaluate the association of head injury with long-term all-cause mortality risk among community-dwelling adults, with consideration of head injury frequency and severity.

Design, setting, and participants: This cohort study included participants with and without head injury in the Atherosclerosis Risk in Communities (ARIC) study, an ongoing prospective cohort study with follow-up from 1987 through 2019 in 4 US communities in Minnesota, Maryland, North Carolina, and Mississippi. Of 15 792 ARIC participants initially enrolled, 1957 were ineligible due to self-reported head injury at baseline; 103 participants not of Black or White race and Black participants at the Minnesota and Maryland field centers were excluded due to race-site aliasing; and an additional 695 participants with missing head injury date or covariate data were excluded, resulting in 13 037 eligible participants.

Exposures: Head injury frequency and severity, as defined via self-report in response to interview questions and via hospital-based International Classification of Diseases diagnostic codes (with head injury severity defined in the subset of head injury cases identified using these codes). Head injury was analyzed as a time-varying exposure.

Main outcomes and measures: All-cause mortality was ascertained via linkage to the National Death Index. Data were analyzed between August 5, 2021, and October 23, 2022.

Results: More than one-half of participants were female (57.7%; 42.3% men), 27.9% were Black (72.1% White), and the median age at baseline was 54 years (IQR, 49-59 years). Median follow-up time was 27.0 years (IQR, 17.6-30.5 years). Head injuries occurred among 2402 participants (18.4%), most of which were classified as mild. The hazard ratio (HR) for all-cause mortality among individuals with head injury was 1.99 (95% CI, 1.88-2.11) compared with those with no head injury, with evidence of a dose-dependent association with head injury frequency (1 head injury: HR, 1.66 [95% CI, 1.56-1.77]; 2 or more head injuries: HR, 2.11 [95% CI, 1.89-2.37]) and severity (mild: HR, 2.16 [95% CI, 2.01-2.31]; moderate, severe, or penetrating: HR, 2.87 [95% CI, 2.55-3.22]). Estimates were similar by sex and race, with attenuated associations among individuals aged 54 years or older at baseline.

Conclusions and relevance: In this community-based cohort with more than 3 decades of longitudinal follow-up, head injury was associated with decreased long-term survival time in a dose-dependent manner, underscoring the importance of measures aimed at prevention and clinical interventions to reduce morbidity and mortality due to head injury.

Figure 1.. Study Timeline and Measures for Atherosclerosis Risk in Communities (ARIC) Study Participants, 1987-2019

CMS indicates Centers for Medicare & Medicaid Services; ED, emergency department; ICD-9, International Classification of Diseases, Ninth Revision; ICD-10, International Classification of Diseases, Tenth Revision. ^aAvailable for all ARIC participants from January 1, 1987, through December 31, 2019. ^bAvailable for ARIC participants aged 65 years or older enrolled in Medicare fee-for-service Part B from January 1, 1991, through December 31, 2018. ^cAvailable for ARIC participants in Minnesota, Maryland, and North Carolina from January 1, 1987, through December 31, 2019, and for ARIC participants in Mississippi from January 1, 1987, through December 31, 2017. ^dQuestions asked in a subgroup of ARIC participants selected for brain magnetic resonance imaging (MRI) scans.

Figure 2.. Cause-Specific Mortality Overall and by Head Injury Status

The number of deaths in each category includes individuals with and without head injuries combined. The percentage of deaths in each category of cause-specific mortality by head injury status with associated 95% CIs was calculated using the exact binomial method.

Figure 3.. Adjusted Hazard Ratios (HRs) for All-Cause Mortality by Number and by Severity of Head Injuries

For both statistical models, follow-up served as the time scale. Head injury was defined as a time-varying covariate, with person-years allocated to no head injury or head injury. All models included controls for sex, race and field center, age, military service, education, income, alcohol consumption, and physical activity. ARIC indicates Atherosclerosis Risk in Communities.