by Dr Isabella Colonna
For November 2021 we have selected Russell ER, Mackay DF, Stewart K, MacLean JA, Pell JP, Stewart W. Association of Field Position and Career Length With Risk of Neurodegenerative Disease in Male Former Professional Soccer Players. JAMA Neurol. 2021 Sep 1;78(9):1057-1063. doi: 10.1001/jamaneurol.2021.2403. PMID: 34338724; PMCID: PMC8329793.
Our research paper of the month is a retrospective cohort study, aiming to investigate the association between field position, professional career length and playing era and increased risk of neurodegenerative disease among male former professional soccer players.
A total of 7676 male former professional soccer players, born between 1.01.1900 and 01.01.1977, and 23028 control individuals matched by year of birth, sex and area socioeconomic status, were included in this study. The group of former soccer players was classified according to field position and professional career length. The era of professional soccer career was determined by dividing the former soccer players group into 2-decade subgroups by year of birth from 1910 to 1969. The outcome was the presence of diagnosis of neurodegenerative diseases, which included Alzheimer’s disease, non-Alzheimer dementia, dementia not otherwise specified, motor neuron disease and Parkinson disease.
Over a median follow-up time of 18 years, neurodegenerative disease diagnoses were found in the 5% of the former professional soccer players and in the 1.6% of the control individuals (HR, 3.66; 95% CI, 2.88-4.65; P < .001). Although former soccer players were more affected by neurodegenerative diseases than the control population, the authors found that this risk varied by field position of the players. While no statistically significant differences were found between goalkeepers and control individuals, outfield players showed higher risk of neurodegenerative disease compared to control population (HR, 3.83; 95%CI, 3.11-4.73; P < .001) and to goalkeepers (odds ratio, 2.22; 95% CI, 1.35-3.64; P = .002). Among the outfield players, this risk was highest for defenders (HR, 4.98; 95% CI, 3.18-7.79; P < .001) and lowest for forwards (HR, 2.79; 95%CI, 2.06-3.78; P < .001). Further, the risk of neurodegenerative disease was highest among the players with the longest careers (HR, 5.20; 95%CI, 3.17-8.51;P < .001), while did not differ across all the birth cohorts for former professional outfield soccer players born from 1910 to 1969 (P = .79).
This cohort study shows that the risk of neurodegenerative disease among former professional soccer players varies according to field position and career length. Outfield players showed higher risk than
control individuals and goalkeepers. This may be explained by the fact that exposure to traumatic brain injury and repetitive head impacts might represent a risk factor for neurodegenerative diseases.
The authors conclude that further studies including amateurs and younger soccer players are needed in order to investigate the association between soccer and neurodegenerative disease.
