HJAR Sep/Oct 2023

HEALTHCARE JOURNAL OF ARKANSAS I  SEP / OCT 2023 27 Based on the well-established use of job exposure matrices to retrospectively char- acterize exposure to occupational hazards among workers 46 , we similarly developed a positional exposure matrix (PEM) to ret- rospectively characterize exposure to RHI among former football players. The PEM was derived from published helmet sen- sor studies that reported findings specific to position and level of play. We used this PEM to calculate CHIIs for deceased former football players whose brains were donated for neuropathological analysis. In addition, we expanded this PEM beyond number of impacts to include average acceleration of impacts, to allow for the calculation of estimated lifetime exposure to linear (CHII- G) and rotational (CHII-R) acceleration. We hypothesized that CHII, CHII-G, and CHII-R would be correlated with the presence and severity of CTE pathology, as well as NFT burden, and that models incorporating the intensity of impacts (CHII-G and CHII-R), would have better model fit and make better predictions of CTE presence, CTE severity, and NFT burden than models that do not incorporate these data (CHII and duration of play alone). We hypothesized that infor- mant-reported concussion number and position would not be associated with CTE presence, CTE severity, or NFT burden. RESULTS Brain donor characteristics A total of 631 brain donors who played American tackle football were included in the study. Characteristics of all brain donors are presented in Tables 1–3. On average, ath- letes died at 59.7 years old (SD = 20.1) and played 12.5 years of football (SD = 5.9). 180 athletes did not have CTE, 163 had low- stage CTE (Stage I or II), and 288 had high- stage CTE (Stage III or IV). The absolute and relative distributions of athlete duration of play by CTE status/severity are presented in Fig. 1 (with distributions for exposure sub- groups presented in Supplementary Fig. 1).