PHILADELPHIA — Professional soccer players appeared nearly twice as likely to develop amyotrophic lateral sclerosis (ALS) as people in the general population, researchers in Italy suggested.
While the overall likelihood of developing ALS was low, the incidence was 1.9 times higher for Italian professional soccer players than the general population, reported Ettore Beghi, MD, of the Mario Negri Institute for Pharmacological Research in Milan, and colleagues, in an early-release abstract from the American Academy of Neurology annual meeting to be held here in May.
Pro players also developed ALS about 20 years earlier than the general population, they added.
There have been several deaths among Italian professional soccer players from ALS, which prompted this research, Beghi noted. “The disease may result at an earlier age as a result of a genetic predisposition combined to environmental factors, as yet ill-defined — among them, multiple traumatic events,” he told MedPage Today.
Professional soccer is not the only contact sport linked to ALS: in the U.S., increasing numbers of National Football League players have been diagnosed with the disease. Previous studies have shown links between repeated head trauma and ALS, although mechanisms are unknown. An association between exercise and ALS has also been proposed, the researchers noted, but results are conflicting. Links between ALS and use of non-steroidal anti-inflammatory agents and dietary supplements, including branched chain amino acids, also have been suggested.
In this study, Beghi and colleagues looked at all professional soccer players who practiced from 1959 to 2000 in the archives of Panini, a major publisher of Italian football trading cards. They followed each player since the year of start of professional activity, noting demographic and career data, and used news reports to determine which players developed ALS. Using a well-defined Italian population as reference, they calculated the number of cases/100,000 person-years that were expected in the cohort
Overall, 33 professional soccer players developed ALS. Based on the reference population, the number of expected cases in the cohort was 17.6.
The median ALS diagnosis age among soccer players was 43.3 years; a median ALS onset age of 62.5 years in the general population. The standardized incidence ratio was 1.9 (95% CI 1.3-2.6) in the entire sample and 4.7 (95% CI 2.7-7.5) in those under age 45 at diagnosis.
“The study is well designed and executed by a world class team of investigators,” observed Robert Miller MD, of the Forbes Norris ALS Research and Treatment Center at California Pacific Medical Center in San Francisco, who was not involved with the analysis.
“The findings are likely correct and should be taken seriously that ALS is two- to five-fold increased in professional soccer players, and probably also in professional football players,” he told MedPage Today. “Although this finding appears dramatic, the vast majority of patients with ALS have no history of playing professional contact sports or repeated head injuries.”
Head injury is a likely factor “as brain injury is definitely not good for the brain,” Miller added, but “the fundamental causes of ALS are still elusive.”
The study looked at professional soccer players only, not amateur players, and had few details about ALS diagnosis, Beghi noted.
This study was supported by Istituto Mario Negri IRCCS.