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J Neurotrauma. 2017 Jan 15;34(2):328-340. doi: 10.1089/neu.2016.4413. Epub 2016 Jun 15.

Cumulative Head Impact Exposure Predicts Later-Life Depression, Apathy, Executive Dysfunction, and Cognitive Impairment in Former High School and College Football Players.

Author information

1
1 Boston University Alzheimer's Disease and CTE Center, Boston University School of Medicine , Boston, Massachusetts.
2
2 Department of Anatomy and Neurobiology, Boston University School of Medicine , Boston, Massachusetts.
3
3 Data Coordinating Center, Boston University School of Public Health , Boston, Massachusetts.
4
4 Department of Neurology, Boston University School of Medicine , Boston, Massachusetts.
5
5 Department of Biostatistics, Boston University School of Public Health , Boston, Massachusetts.
6
6 Concussion Legacy Foundation , Waltham, Massachusetts.
7
7 Framingham Heart Study, Boston University School of Medicine , Boston, Massachusetts.
8
8 Department of Pathology, Boston University School of Medicine , Boston, Massachusetts.
9
9 VA Boston Healthcare System , Boston, Massachusetts.
10
10 Department Neurosurgery, Boston University School of Medicine , Boston, Massachusetts.
11
11 Department of Neurosurgery, Emerson Hospital , Concord, Massachusetts.
12
12 Environmental Health, Boston University School of Public Health , Boston, Massachusetts.

Abstract

The term "repetitive head impacts" (RHI) refers to the cumulative exposure to concussive and subconcussive events. Although RHI are believed to increase risk for later-life neurological consequences (including chronic traumatic encephalopathy), quantitative analysis of this relationship has not yet been examined because of the lack of validated tools to quantify lifetime RHI exposure. The objectives of this study were: 1) to develop a metric to quantify cumulative RHI exposure from football, which we term the "cumulative head impact index" (CHII); 2) to use the CHII to examine the association between RHI exposure and long-term clinical outcomes; and 3) to evaluate its predictive properties relative to other exposure metrics (i.e., duration of play, age of first exposure, concussion history). Participants included 93 former high school and collegiate football players who completed objective cognitive and self-reported behavioral/mood tests as part of a larger ongoing longitudinal study. Using established cutoff scores, we transformed continuous outcomes into dichotomous variables (normal vs. impaired). The CHII was computed for each participant and derived from a combination of self-reported athletic history (i.e., number of seasons, position[s], levels played), and impact frequencies reported in helmet accelerometer studies. A bivariate probit, instrumental variable model revealed a threshold dose-response relationship between the CHII and risk for later-life cognitive impairment (p < 0.0001), self-reported executive dysfunction (p < 0.0001), depression (p < 0.0001), apathy (p = 0.0161), and behavioral dysregulation (p < 0.0001). Ultimately, the CHII demonstrated greater predictive validity than other individual exposure metrics.

KEYWORDS:

behavior; cognition; concussion; football; long-term impairment; subconcussive impacts

PMID:
27029716
PMCID:
PMC5220530
DOI:
10.1089/neu.2016.4413
[Indexed for MEDLINE]
Free PMC Article

Conflict of interest statement

Author Disclosure Statement Dr. Stern is a paid consultant to Amarantus Bioscience, Avanir Pharmaceuticals, and Biogen. He also serves as an expert advisor to attorneys for cases pertaining to the long-term consequences of repetitive brain trauma. He receives royalties from Psychological Assessment Resources for the publication of neuropsychological tests. Dr. Cantu receives compensation from the National Football League as Senior Advisor to the Head, Neck, and Spine Committee; from the National Operating Committee on Safety of Athletic Equipment as Chairman of the Scientific Advisory Committee; and from Concussion Legacy Foundation as co-founder and medical director for some talks given and research conducted. He receives royalties from Houghton Mifflin Harcourt and compensation from expert legal opinion. All other authors report no competing financial interests.

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