Study Raises Concerns About Higher Dementia Risk Among Former Soccer Pros

Question Addressed:

What did an epidemiologic study of former professional soccer players reveal about the potential long-term consequences of playing soccer at the professional level?

Study Synopsis and Perspective:
Two headers reverberated around the world. In 1970, legendary soccer star Pelé leapt over a defender for a head goal that helped Brazil to win its third World Cup title. Abby Wambach's towering header in stoppage time at a 2011 soccer match against Brazil relaunched the U.S. team's efforts to win the Women's World Cup. They are only two of the stars admired and emulated by more than a quarter of a billion people who play this contact sport in over 200 countries. But there may be neurological consequences later in life for heading the ball 6 to 12 times, on average, per game (in addition to heading drills at practice), and thousands of times during a career.

Action Points

Mortality from neurodegenerative diseases was higher and prescriptions for dementia-related medications were more common among former professional soccer players compared with matched controls in a Scottish retrospective epidemiologic analysis.
Note that mortality from other common diseases was lower among former soccer players compared with controls, but realize that these data need to be confirmed in prospective matched-cohort studies.

Researchers have now confirmed these concerns for Scottish former professional soccer players who formed part of the retrospective Football's InfluencE on Lifelong health and Dementia risk (FIELD) study. Compared with matched individuals from the general population, the former professional soccer players had an approximately 3.5 times higher rate of death due to neurodegenerative diseases. Neurodegenerative disease listed as the primary cause of death among former players was 1.7% versus 0.5% in controls (subhazard ratio adjusted for competing risks of death from ischemic heart disease and from any cancer 3.45, 95% CI 2.11-5.62, P<0 .001="" a="" and="" chb="" co-authors="" glasgow="" href="https://www.nejm.org/doi/full/10.1056/NEJMoa1908483" in="" mb="" of="" phd="" reported="" stewart="" target="_blank" the="" university="" willie="">New England Journal of Medicine</0>

. FIELD investigators represented a multidisciplinary collaboration of researchers and experts in traumatic brain injury, public health, and sport. Their purview was to investigate a wide range of physical and mental health outcomes, including neurodegenerative diseases, in former soccer players. Stewart and colleagues evaluated cause of death and use of medications for dementia in 7,676 former players and 23,028 matched controls (matched on the basis of age, sex, and degree of social deprivation).
The median follow-up was 18 years from study entry. The mean ages at death for 1,180 former soccer players (15.4%) and 3,807 matched controls (16.5%) were 67.9 years and 64.7 years, respectively.
Compared with controls, all-cause mortality was lower in former players up to age 70, but higher after that. Former pro athletes had lower death rates from ischemic heart disease (HR 0.80, 95% CI 0.66-0.97, P=0.02) and from lung cancer (HR 0.53, 95% CI 0.40-0.70, P<0 .001="" p="">Neurodegenerative disease listed as a primary or contributory cause of death was highest in former players with Alzheimer's disease (HR 5.07, 95% CI 2.92-8.82, P<0 .001="" 1.17-3.96="" 2.15="" 95="" and="" ci="" disease="" em="" in="" lowest="" parkinson="" s="" those="" with="">P</0></0>
=0.01), compared with controls. Dementia-related medications were prescribed more frequently to former players than to controls (OR 4.90, 95% CI 3.81-6.31, P<0 .001="" p="">A specific form of degenerative brain disease linked to traumatic brain injury, known as chronic traumatic encephalopathy (CTE), has been observed in athletes from a wide range of contact sports. However, because no International Classification of Diseases (ICD)-9 or ICD-10 codes exist for CTE or its synonym, dementia pugilistica, these diagnoses were not available from death certificates reviewed for the study. Other study limitations included possible errors in reporting on death certificates and the possible introduction of bias due to the fact that not all former players identified from the master datasets could be matched to Community Health Index numbers. The researchers also stated that the results were not directly applicable to collegiate, recreational, and amateur players.
Source References: New England Journal of Medicine 2019; DOI: 10.1056/NEJMoa1908483
Editorial: New England Journal of Medicine 2019; DOI: 10.1056/NEJMe1912071
Study Highlights and Explanation of Findings:
Good news and bad news emerged from a retrospective epidemiologic study for former professional soccer players. Mortality from non-neurological diseases was lower among former soccer players up to the age of 70 compared with matched controls from the general population. This unsurprising finding is in keeping with the reduced risk of heart disease and all-cause mortality associated with participation in sports.
However, neurodegenerative disease listed as the primary cause of death was higher among the former soccer players versus controls. Competing risks of death from ischemic heart disease or cancer partially attenuated the findings. In addition, prescriptions for dementia-related medications were more common among former players.
"This is the largest study to date looking in this detail at the incidence of neurodegenerative disease in any sport, not just professional footballers," said Stewart in a statement.
"A strength of our study design is that we could look in detail at rates of different neurodegenerative disease subtypes. This analysis revealed that risk ranged from a 5-fold increase in Alzheimer's disease, through an approximately 4-fold increase in motor neuron disease, to a 2-fold [increase in] Parkinson's disease in former professional footballers compared to population controls," he added.
"An important aspect of this work has been the ability to look across a range of health outcomes in former professional footballers. This allows us to build a more complete picture of health in this population," he said. "Our data show that while former footballers had higher dementia rates, they had lower rates of death due to other major diseases. As such, whilst every effort must be made to identify the factors contributing to the increased risk of neurodegenerative disease to allow this risk to be reduced, there are also wider potential health benefits of playing [soccer] to be considered."
Stewart's group also called for confirmation of these findings in prospective matched-cohort studies.
In an accompanying editorial, Robert Stern, PhD, of Boston University, highlighted the growing body of evidence linking repetitive brain trauma suffered in some contact and collision sports to increased risks of cognitive/neuropsychiatric impairments, as well as the risk of neurodegenerative disease and CTE.
These results are similar to those reported in a study of former National Football League (NFL) players that showed all-cause mortality was lower in former players compared with the general population, but neurodegenerative mortality was higher, he observed.
"Another study involving former NFL players included a comparison group of former Major League Baseball players and found that all-cause mortality, cardiovascular mortality, and neurodegenerative mortality were higher among the former NFL players," Stern added. "These results suggest that factors that vary in these two sports, such as body habitus and exposure to repetitive head impacts, rather than common factors such as overall physical activity could be responsible for the differences."
It seems it's "not just the 'big hits' resulting in symptomatic concussions that increase the risk of neurologic disorders later in life," he wrote. "Rather, the total duration of exposure to repetitive head impacts, including 'sub-concussive' injuries without symptoms, has been associated with neuropathology, in vivo markers of neurodegeneration, and cognitive and neuropsychiatric symptoms later in life."
Stern agreed with the authors that there was a need for further study, such as longitudinal assessments to examine possible relationships between heading and neurodegenerative diseases to confirm or refute current findings. "Perhaps, however, there is already adequate evidence that repeated blows to the brain from heading in professional soccer is an occupational risk that needs to be addressed," he concluded.
Britain's Football Association, which helped fund the research, said it plans to set up a task force to examine potential causes of neurodegenerative deaths among soccer players and while more research is needed, "there is not enough evidence at this stage to make other changes to the way the modern-day game is played."
Although next steps remain a hot topic, it is worth noting that the U.S. Soccer Federation banned headers for children age 10 and under and placed a limit on the same practice for children ages 11 to 13.

Reviewed by Henry A. Solomon, MD, FACP, FACC Clinical Associate Professor, Weill Cornell Medical College

Primary Source

New England Journal of Medicine

Source Reference: Mackay DF, et al "Neurodegenerative disease mortality among former professional soccer players" N Engl J Med 2019; DOI: 10.1056/NEJMoa1908483.

Secondary Source

New England Journal of Medicine

Source Reference: Stern RA "Soccer and mortality -- good news and bad news" N Engl J Med 2019; DOI: 10.1056/NEJMe1912071.

Additional Source

MedPage Today

Source Reference: George J "Dementia Deaths High in Former Pro Soccer Players" 2019.

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