Among football players, odds of having a parkinsonism or Parkinson disease diagnosis were greater with more seasons and higher level of football play.
Recently published data from a cross-sectional study of participants enriched for parkinsonism or Parkinson disease (PD) found an increased risk for the disease among those who participated in football. These findings were consistent after accounting for age, education level, history of diabetes and heart disease, body mass index (BMI), traumatic brain injury with loss of consciousness, and family history of PD.1
Published in JAMA Network Open, the study featured 1875 men (mean age, 67.69 years) who completed online questionnaires and self-reported whether they currently had a diagnosis of PD or parkinsonism by a physician or other health care professional. Of these, 729 (38.9%) participants played football for a mean duration of 4.35 (SD, 2.91) years. Using logistic regression models, a history of playing football was associated with a higher odds of having a parkinsonism or PD diagnosis, with an odds ratio (OR) of 1.61 (95% CI, 1.19-2.17).
"The cause of parkinsonism and PD in former football players is multifactorial and related to factors associated and unassociated with exposure to repetitive head impact," lead investigator Hannah Bruce, MS, a clinical research assistant at Boston University School of Medicine, and colleagues, noted. "Duration of play, a proxy for exposure to repetitive head impact, has been associated with chronic traumatic encephalopathy status and severity."
To the authors knowledge, this was the largest study to describe the association between participation in football and odds of having a reported diagnosis of parkinsonism or PD. In addition to football, some patients participated in other contact sports such as soccer (23.7%), ice hockey (9.2%), amateur wrestling (6.1%), and boxing (4.9%). Of the total sample of 1875 participants, 1602 (85.4%) reported having a parkinsonism or PD diagnosis.
Among those who played football, most played at the youth or high school level (82.4%), followed by some who played in college (16.9%) and few who played at a professional or semiprofessional level (0.7%). Not only was playing football associated with higher odds of having a reported parkinsonism or PD diagnosis, but longer durations of football play increased these odds (OR, 1.12 per season played; 95% CI, 1.06-1.19). Having a low exposure (n = 435) was associated with a 1.39 (95% CI, 0.98-1.98) increase in odds of having a reported parkinsonism or PD diagnosis compared with a 2.18 OR (95% CI, 1.36-3.49) for those with substantial exposure (n = 252).
While higher levels of football play were associated with greater risk for these outcomes (OR, 2.93; 95% CI, 1.28-6.73), age at first exposure to football (mean, 12.66 [SD, 2.39] years) was not (OR, 1.04; 95% CI, 0.93-1.17). After excluding participants who participated in boxing, soccer, or ice hockey, playing football was still associated with a higher odds of having a reported parkinsonism or PD diagnosis (OR, 1.65; 95% CI, 1.13-2.41).
The study had several noted limitations, led by the homogenous demographic make-up of the sample, which included 98% White participants. Patients were pulled from the Fox Insight online study, which has minimal eligibility criteria and includes people with and without PD. By nature, people who are at risk or have concerns for PD were more likely to participate.
"Parkinsonism and PD were not separately queried, and we were unable to differentiate if the current associations or lack thereof pertain to parkinsonism or PD," the study authors wrote. "Former football players are more prone to orthopedic injuries, particularly those who played at elite levels. While focus on parkinsonism and PD diagnosis attenuates concerns for orthopedic injuries as confounding, it remains a potential cause of motor abnormalities."