A Decision-Analytic Approach to Addressing the Evidence About Football and Chronic Traumatic Encephalopathy.

Area of Science:

• Neurology
• Sports Medicine
• Public Health

Background:

• Establishing causality between exposures and adverse health effects is complex, even for well-accepted links like smoking and lung cancer.
• Appraising evidence requires considering alternative hypotheses and the consequences of false positives versus false negatives.

Purpose of the Study:

• To evaluate the weight of evidence linking repeated head impacts (RHIs) in professional football to chronic traumatic encephalopathy (CTE).
• To assess the subsequent risk of cognitive and behavioral symptoms resulting from RHI-induced CTE.

Main Methods:

• Dismissal of four common logical fallacies that could bias evidence appraisal.
• Examination of four alternative hypotheses suggesting RHI is not causally linked to CTE or its symptoms.

Main Results:

• The evidence strongly suggests a causal link between RHIs and CTE, with symptoms being unlikely to be coincidental or artifactual.
• Alternative hypotheses were found to be less probable explanations for the observed association.

Conclusions:

• The association between repeated head impacts and chronic traumatic encephalopathy, leading to cognitive and behavioral symptoms, is supported by substantial evidence.
• The public health costs of inaction (false negatives) outweigh the costs of intervention (false positives) even with a skeptical appraisal.