Mortality Risk from Neurodegenerative Disease in Sports Associated with Repetitive Head Impacts: Preliminary Findings from a Systematic Review and Meta-Analysis

Background Professional athletes seem to have a lower overall mortality risk than the general population, but controversy exists about whether athletes in sports associated with repetitive head impacts have a higher risk of mortality from neurodegenerative diseases. Objective We aimed to determine the risk of mortality from neurodegenerative diseases in sports associated with repeated head impacts compared with the general population or compared with athletes with no such exposure. Methods We conducted a systematic review with meta-analysis, systematically searching PubMed, Web of Science, Scopus, and SPORTDiscus (since inception to 14 May 2021) for studies comparing the risk of death from neurodegenerative disease in athletes participating in contact sports in which their heads recurrently receive blows from the bodies of other participants or from a ball versus a control group or dataset representing the general population. Results Six moderate- to high-quality retrospective studies including data from 41,699 athletes participating in contact sports (boxing, basketball, ice hockey, American Football and soccer) met all inclusion criteria to be included in the systematic review. Of these, three studies ( N = 37,065 male professional soccer players) could be meta-analysed. Despite no differences in the risk of all-cause ( p = 0.138), cardiovascular ( p = 0.085) and cancer-related mortality ( p = 0.136), soccer players presented with a significantly higher mortality risk from motor neuron disease (standard mortality rate 8.43; 95% confidence interval 3.07–23.13; p