This study by Bruce et al examined data from an online study of people with Parkinson’s disease and age-matched control volunteers. The authors used online questionnaires to assess the participant’s history of playing American Football and whether they were diagnosed with Parkinson’s disease. 

The results suggest that in this sample enriched for Parkinson’s disease, a history of playing American Football was associated with higher odds of having a Parkinson’s disease diagnosis. Of those in the study who played American Football, those who had played for longer or at a higher level had higher odds of having Parkinson’s disease.

These results echo similar findings for Chronic Traumatic Encephalopathy (CTE), a type of dementia linked to repetitive head injury exposure. The duration of American Football play is considered a proxy for exposure to repetitive head impacts and is associated with the development of CTE. A growing body of evidence supports the increased risk of developing a neurodegenerative disease for people exposed to repeated head injuries. This study suggests that the relationship between head injuries and developing Parkinson’s disease should be further explored. Studies examining the incidence of Parkinson’s disease in the wider contact sports community should be conducted to clarify these findings.

While the study is focused on American Football, these findings are relevant to all contact sports athletes. It is unclear whether these findings will be applicable to female athletes or amateur athletes. This is a limitation of all current studies as we have very little data on these groups. The collection of this data should be a priority as womens sport and amateur sport grows and it is vital that we understand whether the long-term risk of neurodegenerative disease differs in these populations.

This study is valuable for us in New Zealand due to the popularity of rugby and other contact sports. The findings of this study emphasise the importance of developing strategies to reduce exposure to head impacts in training and games and to be cautious in our approach to head injury management and return to play. We should also investigate strategies to proactively monitor and improve the brain health of contact sports athletes during and after their athletic careers. This study also highlights the need for additional research exploring the mechanisms of how head injuries alter the brain and how these changes can progress into neurodegeneration. Here at the University of Auckland Centre for Brain Research, we have developed the sports brain bank initiative as part of the Neurological Foundation Human Brain Bank. We are studying the donated brain tissue of deceased former athletes with and without cognitive symptoms to understand how repetitive head injury exposure alters the brain's microscopic structure.

This cross-sectional study of 1875 former male athletes compared the 38.9% who played American football with 62.1% in other sports. Their self-reported or medically diagnosed Parkinson disease or parkinsonism, and their exposure to sport (years, playing level, age first started playing) was compared. Those who played at higher levels of American football were 2.9 times more likely to report Parkinson disease or parkinsonism compared with former players of other sports. Those who played sports for more years, no matter what sport, were 1.12 times more likely to report having been diagnosed with Parkinson disease or parkinsonism than those who had played for less years.

Therefore, we can conclude from this study that exposure to impacts in sport – from either higher magnitude impacts in American football, or more impacts over additional years of playing sport – is more likely to lead to a diagnosis of Parkinson disease or parkinsonism than those with less brain impact exposure.