Professional soccer increases risk for neurodegenerative disease later in life

Neurodegenerative disease diagnoses occurred more often among former soccer players than the general population, with defenders experiencing the highest risk, according to results of a cohort study published in JAMA Neurology.

“Although data suggest [traumatic brain injuries] are infrequent in soccer, training and gameplay routinely involve exposure to repetitive head impacts through soccer ball heading,” the researchers wrote, noting the sport’s global popularity.

Emma R. Russell, MSc, of the Institute of Neuroscience and Psychology, University of Glasgow, and colleagues aimed to determine the link between field position, professional career length and playing era with risk for neurodegenerative disease among male former professional soccer players. The researchers examined data from 7,676 former soccer players in the Scotland men’s professional leagues born between Jan. 1, 1900, and Jan. 1, 1977. They matched players to 23,028 men in the general population in a 1:3 ratio with the same birth year and socioeconomic status, for a total of 1.8 million person-years of follow-up.

The study grouped players according to their primary field position, either goalkeeper or outfielder, as well as professional career length and era of play. Defenders, midfielders, forwards and multiposition constituted outfielder subdivisions. The researchers obtained data on unspecified dementia, Alzheimer’s disease, non-Alzheimer’s dementia, motor neuron disease and Parkinson disease in living and deceased individuals.

Russell and colleagues found that a higher percentage of former professional soccer players were diagnosed with neurodegenerative disease than the general population (5% vs. 1.6%; HR, 3.66; 95% CI, 2.88-4.65). Outfielders experienced a higher risk than the general population (HR, 3.83; 95% CI, 3.11-4.73), which was higher than the risk seen among goalkeepers (OR, 2.22; 95% CI, 1-.35-3.64). Among outfielders, forwards demonstrated the lowest level of risk (HR, 2.79; 95% CI, 2.06-3.78) and defenders had the highest (HR, 4.98; 95% CI, 3.18-7.79).

Players with shorter careers experienced the lowest risk for neurodegenerative disease compared with controls (HR, 2.26; 95% CI, 1.51-3.37), while those with the longest careers had the highest risk (HR, 5.2; 95% CI, 3.17-8.51). The researchers observed no statistically significant risk difference between eras of play.

Limitations of the study included lack of information on players’ participation in non-professional soccer and other sports, including other contact sports, and lack of data on soccer participation in the general population, which may be associated with risk for neurodegenerative diseases, according to the researchers.

“There is a need for further studies to interrogate the association between soccer and neurodegenerative disease, including risks in amateur and youth soccer,” Russell and colleagues wrote. “Meanwhile, adopting a precautionary principle approach to mitigate risk of neurodegenerative disease by reducing exposure to TBI and head impacts in soccer and wider sports might be advised.”

In a related editorial, Breton M. Asken, PhD, ATC, a neuropsychology fellow at the Memory and Aging Center in the department of neurology at the University of California, San Francisco, and Gil D. Rabinovici, MD, the Edward Fein and Pearl Landrith Endowed Professor in Memory & Aging at the Memory and Aging Center at UCSF, noted that the evidence linking professional soccer participation with dementia later in life is “rapidly growing, revealing an ugly side to the beautiful game.” These findings warrant an “unequivocal call” for soccer’s governing bodies to decrease the long-term risks for negative health outcomes in these players, Asken and Rainovici noted.

“... Brain protection in soccer should be feasible without fundamentally changing the game,” they wrote. “Efforts to study and protect the brain health of all soccer players will provide the best chance for preserving the longevity of this beloved sport.”