Table 5.

Summary of results from studies reporting data on the frequency of CTE

Characteristics					Quality assessment			Summary of findings
								N. of subjects		Results
Fist author, year	Sport	Source of cases	Reference population	Exposure	Selection	Comparability	Outcome/exposure	n. cases among the exposed/total exposed	n. cases among the reference group/total reference	Data ORs/HRs (95%CIs) or SIRs/PRs/SMRs/SPMRs
Cohort studies
Bieniek 2019 [80]	Baseball Basketball Boxing American football Hockey Soccer Wrestling	Mayo Clinic Tissue Registry	consecutive autopsies from the Mayo Clinic Tissue Registry with available information on sport participation	information on sport participation and participation age/level/duration taken from high school yearbooks or obituaries	***	–	***	300 athletes CTE positive:r 15 athletes CTE features: 12	450 non-athletes CTE positive: 6 CTE features: 9	OR* for combined CTE pathology (males) adj for age at death, baseball, boxing, and American football American football beyond high school OR = 13.23 (4.23, 41.36) p < 0.001 OR for combined CTE positive (CTE +) (males) adj for boxing and American football boxing OR = 10.29 (1.79, 59.28) p = 0.009 American football OR = 2.87 (1.17, 7.01) p = 0.021 American football beyond high school OR = 6.84 (1.76, 26.66) p = 0.0056

OR odds ratio

*Only adjusted data reporting statistically significant differences have been reported