THE EFFECTS OF HEAD TRAUMA AND MODIFIABLE LIFESTYLE FACTORS ON NEUROLOGICAL HEALTH IN MATURE ADULTS

Abstract

BACKGROUND: Repetitive head impacts (RHI) in contact sports are common and pose significant health concerns, particularly regarding their long-term effects on aging populations. Research highlights associations with increased risk of neurological impairments and neurodegenerative disease among those with RHI exposure. However, much of the research has focused on professional-level athletes, such as American football, with the long-term effect of RHI in amateur athletes, who represent the vast majority of contact/collision sport participation, largely unexplored. Additionally, age-related declines in postural control threaten functional independence and well-being, yet understanding postural control impairments in aging populations with RHI exposure remains limited. RHI's effects on neurological health can impact health-related quality of life (HRQoL) and requires comprehensive investigations that consider diverse sports groups and age cohorts, as current literature often overlooks these factors. Recognizing the multifactorial nature of cognitive decline and functional impairments, evaluating modifiable personal risk and protective factors using tools like the Lifestyle for Brain Health (LIBRA) risk score offers insights into moderating RHI's impact on aging populations. PURPOSE: The overall purpose of this dissertation was to identify potential consequences of RHI on later life neurological health with consideration of key modifiable lifestyle risk factors to identify their influence on former amateur contact/collision sport athletes. METHODS: For Aim 1, 87 former collegiate ice hockey players (Age: 52.216.9, range: 24.0-82.0) completed an online survey assessing demographics, sport and concussion history, and neurological health outcomes, including QoL (12-Item Short-Form Survey (SF-12 Physical and Mental Component Summary (PCS/MCS), Satisfaction with Life Scale (SFWLS), Apathy Evaluation Scale (AES)), cognitive function (PROMIS Cognitive Function Short Form-4a), and neurobehavioral symptoms (Neuro-QoL Emotional and Behavioral Dyscontrol (EBD) Short Form Questionnaire, Center for Epidemiological Studies Depression Scale (CES-D), Rivermead Post-Concussion Symptom Questionnaire (RPSQ), Adverse Childhood Events (ACE) Questionnaire for Adults). Modifiable lifestyle-related risk and protective factors were quantified using the Lifestyle for Brain Health (LIBRA) risk score. Multiple linear regression models were used to examine the associations between each independent variable (career duration, concussion history, and LIBRA score) and neurological health outcomes, adjusting for age as a covariate. For Aims 2 and 3, 75 mature and older adults (>50 years) were recruited into three groups: former contact/collision sport athletes with high risk for repetitive head impact exposure (HRS; N = 25, 59.2±6.2 years), physically active former non-contact athletes (NCA; N = 25, 62.0±7.9 years), and physically inactive non-athletes (NON; N = 25, 63.3±8.0 years). Participants performed instrumented single-task and dual-task gait and gait initiation conditions in a motion capture laboratory. Dual-task costs (DTC) were calculated for gait initiation, gait, and cognitive variables to determine task prioritization. Group differences were evaluated using multiple one-way ANOVAs or Kruskal-Wallis tests for non-normally distributed measures. Significant main effects were followed up with either a Kruskal-Wallis test with pairwise comparison procedure or a Tukey post hoc. For Aim 3, linear regression models were used to examine the association between LIBRA score and DTC outcomes. RESULTS: For Aim 1, concussion history was significantly associated with poorer cognitive and neurobehavioral outcomes across multiple measures. Each additional concussion was associated with lower (worse) PROMIS Cognitive Function scores (β = –0.85, R² = 0.15, p = 0.002), lower SF-12 Mental Component Summary scores (β = –0.78, R² = 0.12, p = 0.011), and higher (worse) symptom burden across emotional and behavioral measures, including EBD, RPSQ, CES-D, and ACE scores (all p < 0.05). Dose–response relationships were observed for concussion history and EBD, RPSQ, and PROMIS Cognitive Function scores, whereby participants reporting ≥10 concussions demonstrated significantly worse outcomes compared to those reporting fewer or no concussions. Higher (worse) LIBRA scores were also significantly associated with poorer cognitive, emotional, and HRQoL outcomes, including lower PROMIS Cognitive Function and SF-12 MCS scores, greater depressive symptoms, higher emotional–behavioral dyscontrol, and greater symptom burden (all p < 0.05). Career duration was not a significant predictor of any cognitive, emotional, or HRQoL outcome (p > 0.05). For Aim 2, a significant group difference was observed for dual-task cost of medio-lateral center-of-mass (COM) displacement during steady-state gait (p = 0.049, η² = 0.06). Specifically, the HRS group demonstrated greater (worse) DTC compared to the NON group (HRS: 17.16 ± 21.34; NON: 2.45 ± 21.05; p = 0.044, d = 0.69). No other significant group differences were observed for gait initiation, steady-state gait, or cognitive DTC outcomes. For Aim 3, LIBRA score was not significantly associated with gait initiation, steady-state gait, or cognitive DTC outcomes (p > 0.05). DISCUSSION: Overall, these findings suggest that RHI exposure from amateur contact and collision sport participation is not associated with widespread impairments in cognitive function, HRQoL, or gait performance in later adulthood. Across aims, concussion history and modifiable lifestyle-related risk factors demonstrated more consistent associations with neurological and self-reported outcomes than measures of cumulative sport exposure, such as career duration. These results suggest that years of participation may inadequately capture individual variability in lifetime RHI exposure. Although gait and DTC performance were largely preserved, a modest increase in DTC of M/L COM was observed in former RHI athletes under DT conditions. While small and within normative ranges, this finding may reflect subtle alterations in motor control that emerge only under increased task complexity. Lifestyle-related risk factors were strongly associated with cognitive and emotional outcomes but were not related to DTC performance. Taken together, these results support a multifactorial framework for neurological aging, in which long-term outcomes among former athletes are influenced more strongly by concussion burden and modifiable lifestyle factors than by amateur contact sport participation alone.