Playing football may increase risk for Parkinson's disease, study says

NEW YORK, Aug. 11 (UPI) -- Playing football may increase the risk for Parkinson's disease -- and that risk rises with more years of participation, even among high school and college athletes, a new study finds.

Using a large online data set of people concerned about developing the disease, the researchers found that participants with a history of playing organized tackle football had 61% increased odds of having a reported parkinsonism or Parkinson's diagnosis.

The study was conducted at Boston University's Chronic Traumatic Encephalopathy Center and published Friday in JAMA Network Open.

"Identifying risk factors for PD [Parkinson's] is essential for early detection and diagnosis," corresponding author Michael L. Alosco told UPI via email. Alosco is an associate professor of neurology at Boston University Chobanian & Avedisian School of Medicine.

"Among a cohort of people at risk for PD, our findings suggest that playing American football might contribute to additional risk for developing this brain disease, although many environmental, genetic and other risk factors are at play," Alosco said.

He added that not everyone who plays tackle football will develop later-life neurological conditions.

Described in boxers

Since the 1920s, Parkinson's disease and parkinsonism -- an umbrella term that refers to motor symptoms present in this disease and other conditions -- have been described as a prominent feature in boxers.

Playing tackle football also can result in long-term neurological consequences, such as chronic traumatic encephalopathy, a brain disorder likely caused by repeated head injuries and blows to the head.

"Our center is most known for our research that has linked history of football play with risk for chronic traumatic encephalopathy," Alosco said. "However, recent research from our center has linked repetitive head impacts with pathologies that cause parkinsonism.

"Large studies in human participants that investigate the association between football and risk for parkinsonism have not yet been done. Therefore, we sought to address this knowledge and test the relationship between playing football and parkinsonism."

Largest study

Center officials noted that this is the largest study to delve into the association between participation in football and the odds for having a reported diagnosis of Parkinson's.

They evaluated 1,875 sport participants -- 729 men who played football, mainly at the amateur level, and 1,146 men who engaged in non-football sports and served as the control group.

The participants' mean age was 67.69 years -- 67.42 for those with Parkinson's versus 63.47 for those without the disease.

The Michael J. Fox Foundation for Parkinson's Research sponsored the longitudinal online study, called Fox Insight, of people with and without Parkinson's.

"One of the major strengths of this study, from a public health standpoint, is that it includes a large population of men who participated in youth football," Dr. Sara Gould, who was not involved in the study, told UPI via email.

Gould is an associate professor in the department of orthopedic surgery and the department of emergency medicine at the University of Alabama at Birmingham.

"Many studies to date are focused on professional athletes, which results in a research gap on the effects of football on amateur athletes," Gould said.

"Given the millions of people who participate in amateur football leagues, and the health consequences of a diagnosis of PD/parkinsonism, it is imperative to continue exploring potential links through research."

Even after accounting for Parkinson's known risk factors, researchers in this study still found a link between playing football and increased odds for having a parkinsonism or a Parkinson's diagnosis.

Longer careers increased odds

The data also revealed that players with longer careers and who participated at higher levels of competition experienced elevated odds for having a reported diagnosis of parkinsonism or Parkinson's.

Those who played at the college or professional level were at 2.93 increased odds for having a Parkinson's diagnosis compared with those who only played at the youth or high school level.

Age of first exposure to football was not associated with odds for having a reported parkinsonism or a Parkinson's diagnosis.

"This was an interesting study suggesting an association between prior football participation and Parkinson's disease, where individuals with a longer duration of prior football participation were more likely to have Parkinson's disease," Dr. Andrea Schneider, who was not involved in the research, told UPI in a telephone interview.

Schneider is an assistant professor in the division of neurocritical care within the department of neurology at the University of Pennsylvania Perelman School of Medicine.

"Overall, this study expands upon the growing research showing associations between contact and collision sports participation and traumatic brain injury, with neurological outcomes," Schneider said.

Mild concussions not worrisome

People should keep in mind that three or four mild concussions do not cause Parkinson's. "These are athletes that repeatedly hit their heads hard on a constant basis," Franklin Brown, chief of the neuropsychology division at Yale Medicine in New Haven, Conn, told UPI via email.

"The general population should not worry about this if they get a few mild concussions or hits to their heads."

Being aware of the risks is important in choosing a sport, "but for some athletes the risk is part of the enjoyment," said Brown, who has provided evaluations for players as part of the NFL Concussion Settlement.

In 2013, the NFL has reached a settlement over concussion-related brain injuries among its 18,000 retired players. The league agreed to compensate victims, pay for medical exams and underwrite research. As of Monday, the NFL paid $1.2 billion in monetary awards to affected players.

Brown added that improvements have been made in helmets -- an area of progress that merits focus. "It will also be helpful for athletes to sit out some games if they have had a concussion," he said.

Meanwhile, Schneider noted that people in the study were not representative of the general U.S. population and suggested that future investigations cast a wider net. In addition, "as the authors clearly note, this study cannot address causality, but the findings do underscore continued attention to safety in sports," she said.

In acknowledging that the sample was selective, Alosco said limitations exist for the study's generalizability. Participants were 98% white, and the diagnosis of Parkinson's was also self-reported through online assessments; objective in-person evaluations were not conducted.

85% already diagnosed

Also, Gould pointed out that 85% of participants already were diagnosed with Parkinson's or parkinsonism at the time of study, which reflects sampling bias. Another factor may be recall bias, which means that people may not remember details of distant events they were questioned about in the survey.

Gould noted that "the way the sports were classified as contact or noncontact is somewhat of a departure from other publications." The sensitivity analysis of non-football repetitive head impact sports only included boxing, soccer and ice hockey. Wrestling, lacrosse, rugby and other high repetitive head impact sports were not excluded.

"Also," she added, "they defined certain sports as non-contact that are generally defined as contact sports. For example, they describe basketball as non-contact, whereas studies by the Centers for Disease Control and Prevention have described basketball as a contact sport.

"This classification of sports that the authors used in their analysis makes it harder to understand the relationship between the sport and head impact on their findings."

Despite the study's limitations, Alosco said it "provides additional evidence of the long-term neurological effects of American football."

"Continued education about the potential long-term risks of American football on the brain to players, coaches and parents is advised, so that informed decisions regarding participation can be made," he said.