In a recent study published in JAMA Network Open, a group of researchers investigated if heading frequency is associated with cognitive impairment in retired soccer players.
In professional soccer players, concerns often arise about the impact of repetitive brain injuries from heading the ball on neurocognitive function. Mild traumatic brain injury (TBI) may increase dementia risk in players who are over the age of 65 years.
Chronic subconcussive trauma from heading during matches and training could elevate the risk of neurodegenerative diseases like chronic traumatic encephalopathy.
Some big studies highlight higher neurodegenerative disease risks in retired players, with defenders at the greatest risk and goalkeepers at the lowest. Despite this, comprehensive information on heading and concussion exposure is lacking.
About the study
The study was conducted between August 2020 and December 2021 and involved retired male professional soccer players over the age of 45 years. A total of 878 retired players meeting the inclusion criteria were sent questionnaires, and those willing to participate completed the questionnaire and underwent cognitive function tests.
Heading exposure data were collected using three bands (0-5, 6-15, and >15 times per typical match and training session). Concussion history and other soccer-related risk factors were also examined.
Cognitive function was assessed using various tests, including the telephone interview for cognitive status-modified (TICS-m), verbal fluency (VF), the Hopkins Verbal Learning Test (HVLT), and independent activities of daily living (IADL). The study also recorded physician-diagnosed dementia/Alzheimer's disease through self-reporting.
The study considered various covariates, such as age, body mass index (BMI), hearing loss, smoking, alcohol consumption, and comorbidities, which could affect dementia risk. Statistical analysis involved calculating prevalence, odds ratios (ORs), and adjusted ORs (AORs) while adjusting for confounding factors.
In the present study, 554 out of 878 questionnaires were returned, and 468 were completed, with 459 reporting heading frequency data. The participants had a mean age of 63.68 years and a BMI of 27.22. The study population was considered representative of the source population. Heading frequency per match was correlated with heading frequency per training.
The authors reported that the occurrence rate of cognitive impairment was 9.78% for players with 0-5 headings per match, 14.78% for 6-15 headings, and 15.20% for >15 headings (P = .51). Compared to players with 0-5 headings, those reporting 6-15 headings had an AOR of 2.71 for cognitive impairment, while players with >15 headings had an AOR of 3.53 (P = .03 for trend).
Similar results were observed for heading frequency per training. The risk of cognitive impairment increased with cumulative heading frequency when considering both matches and training.
Other risk factors associated with cognitive impairment were playing position, with defenders having the highest risk, and concussion involving loss of memory. Heading frequency per match and training was also associated with other cognitive impairment outcomes, such as a TICS-m score of 23 or lower, IADL, and self-reported dementia/Alzheimer's disease.
Linear regression analysis supported these associations for TICS-m, IADL, and Test Your Memory (TYM) scores.
The study was the first to primarily investigate the association between heading frequency during a professional soccer player's career and long-term cognitive impairment and self-reported dementia/Alzheimer's disease.
The researchers reported that both match and training heading frequencies were linked with a risk of cognitive impairment, and the risk increased with higher heading frequencies. These associations were consistent across different cognitive function tests.
Further, the findings aligned with other studies that used playing position as a substitute for head impact exposure and found higher neurodegenerative disease risks in defenders compared to goalkeepers. The authors of this study suggested that heading exposure was a contributing factor, and their results supported this, with defenders heading the most, followed by forwards, midfielders, and goalkeepers.
The study results also indicate that repetitive subconcussive trauma from heading can have a cumulative effect on brain health, supported by autopsies of athletes involved in contact sports. The study used broad bands for measuring heading frequency (0-5, 6-15, and >15 per match and training session) and found that heading more than 15 times on both occasions increased the risk of cognitive impairment compared to heading 0-5 times.
While concussions alone were not associated with cognitive impairment, concussions involving memory loss were linked to cognitive impairment. These findings emphasized the need to reduce exposure to head impacts and repetitive subconcussive head injuries in soccer players to protect brain health.
To summarize, the study findings provide evidence that repetitive heading in professional soccer players is associated with an increased risk of cognitive impairment and self-reported dementias in later life.
The study highlights the importance of considering heading frequency as a risk factor and calls for further research to determine a safe maximum heading frequency per match and training session that can help mitigate this risk.