The Atherosclerosis Risk in Communities (ARIC) Study is an ongoing prospective cohort study comprised of 15,792 community-dwelling adults in the U.S. who were initially recruited in 1987–1989. History of TBI was defined using self-report and hospital-based diagnostic codes and was analyzed as a time-varying exposure. Episodic depressive symptoms and prescribed antidepressants were assessed at Visits 5 (2011–2013), Visit 6 (2016–2017), and Visit 7 (2018–2019). Depressive symptoms were measured using the Center for Epidemiologic Studies Depression (CESD) scale 11-item version, with a cut-point of ≥9 used to define clinically significant depressive symptoms. We used generalized estimating equations (GEE) with an autoregressive working correlation structure and a binomial distribution with a log link to estimate risk ratios (RR) for the association of head-injury with time-varying depressive symptoms and prescribed anti-depressants, adjusting for age, sex, race/center, educational attainment, household income, and prior military service.  

Of the 6,607 participants included the median age was 75 years (25^th-75^th percentiles=72–80). More than half were female (59.0%) and 23.7% were Black. There were 2,113 participants (32.0%) with history of TBI, most of which were classified as mild. In adjusted GEE models, history of TBI was associated with increased risk of episodic depressive symptoms (RR=1.59, 95%CI: 1.37–1.85) and prescribed antidepressants (RR=1.32, 95%CI: 1.20–1.45) over Visits 5–7. These results persisted in analysis of subgroups defined by age, sex, and race.