Early detection of Parkinson's disease (PD) necessitates the identification of risk factors. Parkinson's disease and parkinsonism—an umbrella term for motor symptoms seen in Parkinson's disease and other conditions—have been observed in boxers since the 1920s. 

Repetitive head hits in tackle football can also result in long-term neurological repercussions such as chronic traumatic encephalopathy (CTE). However, data on the link between tackle football activity and Parkinson's disease is sparse.

Researchers from the BU CTE Centre used a large online data set of people concerned about having PD to conduct the largest study to describe the association between participation in football and the odds of having a reported diagnosis of PD.

They discovered that participants with a history of playing organised tackle football had a 61% increased odds of having reported parkinsonism or PD diagnosis.

In this study, the researchers evaluated 1,875 sports participants — 729 men who played football, predominantly at the amateur level, and 1,146 men who played non-football sports who served as the control group.

Participants were enrolled in Fox Insight, a longitudinal online study of people with and without PD sponsored by The Michael J. Fox Foundation for Parkinson’s Research.

Notably, researchers found a link between playing football and increased odds of having a parkinsonism or PD diagnosis even after accounting for known risk factors for PD.

Additionally, the data revealed that players who had longer careers and played at higher levels of competition experienced increased odds of having a reported diagnosis of parkinsonism or PD.

Football players who played at the college or professional level were at 2.93 increased odds of having a PD diagnosis compared with those who just played at the youth or high school level. The age of first exposure to football was not associated with the odds of having reported parkinsonism or PD diagnosis.

Playing tackle football could be a contributing risk factor to PD, particularly among people already at risk due to other factors (e.g., family history).

However, the reasons for this relationship are not clear and we also know that not everyone who plays tackle football will develop later-life neurological conditions, meaning many other risk factors are at play, says corresponding author Michael L. Alosco, PhD, associate professor of neurology at Boston University Chobanian & Avedisian School of Medicine.

The researchers also emphasised that they compared the football players to another group of athletes, a noteworthy strength of the study. Furthermore, most of the participants played tackle football only at the amateur level, which is in contrast to most of the research to date that has focused on professional athletes.

“Previous research has focused on the association between American football and risk for CTE. However, similar to what has historically been seen in boxers, American football might also affect risk for other neurodegenerative conditions such as PD,” says Hannah Bruce, MSc, first author and research specialist at Boston University Chobanian & Avedisian School of Medicine.