Association of Lifetime Traumatic Brain Injury and Military Employment with Late-Life ADL Functioning: A Population-Based Prospective Cohort Study

Abstract

<h3>Research Objectives</h3> To determine associations of lifetime history of traumatic brain injury (TBI) with loss of consciousness (LOC) and military employment with activities of daily living (ADL) in late life. <h3>Design</h3> A population-based prospective cohort study of older adults with a baseline visit and up to 10-years of biennial follow-up visits. <h3>Setting</h3> Seattle-area integrated healthcare delivery system. <h3>Participants</h3> Male (n=2066) and female (n=2887) participants of the Adult Changes in Thought (ACT) study, aged 65+ and dementia-free. <h3>Interventions</h3> We fitted repeated-measures Poisson mixed effects regression models. Military employment and TBI with LOC variables were included as main effects. We included interaction terms with time to allow for different longitudinal trends in ADL difficulties within each exposure group of interest. <h3>Main Outcome Measures</h3> History of TBI with LOC was based on participant self-report during the baseline visit. History of military employment was ascertained based on items addressing the longest and second longest occupations for each participant. ADL functioning was assessed at baseline and biennial follow-up via participant self-reported function on the 6-item Katz ADL index. For analyses, we summed the number of ADLs with which a person reported at least some difficulty (range 0-6). <h3>Results</h3> TBI with LOC before age 40 was associated with greater ADL difficulty at baseline for females (RR=1.44, 95% CI: 1.08-1.93, p=0.01). For males, TBI with LOC at any age was associated with greater ADL difficulty at baseline (age < 40: RR=1.58, 95% CI: 1.20 - 2.08, p = 0.001; age 40+: RR=2.14, 95% CI: 1.24 - 3.68, p = 0.006). TBI with LOC was not associated with the rate of accumulation of ADL difficulties over time in males or females. There was no evidence of an association between military employment and either outcome, nor of an interaction between military employment and TBI with LOC. Findings were consistent across a variety of sensitivity analyses. <h3>Conclusions</h3> Future study of the implications of TBI and military employment on late-life physical functioning as measured by performance-based tools in more diverse cohorts is warranted. <h3>Author(s) Disclosures</h3> No conflicts of interest reported.