A new Lancet study of elite Swedish football players is the latest addition to a mounting pile of science linking high-level sports to the development of neurodegenerative conditions.

The observational study tracked over 6,000 male footballers in Sweden’s top professional league between 1924 and 2019. It found they were 1.5 times more likely to develop neurodegenerative diseases than their non-footballing counterparts.

Concerns about the impact of professional sports on the brains of athletes have risen sharply in the past decade. Alarm bells rung out over the American football world as early as 2007.

Yet before the publication a 2017 paper by researchers at University College London, only four (European) football players were known to have had chronic traumatic encephalopathy (CTE).

Today, that number is in the thousands.

Repeated head trauma

The Swedish study adds to observational data on a cohort of Scottish pro-footballers published in the New England Journal of Medicine in 2021, which found the athletes were three and a half times more likely to develop neurodegenerative diseases than the control group.

They were also three times more likely to have a neurodegenerative disease listed as their cause of death than an average person.

In both studies, overall mortality was found to be slightly lower among the footballers.

“While the risk increase in our study is slightly smaller than in the previous study from Scotland, it confirms that elite footballers have a greater risk of neurodegenerative disease later in life,” Peter Ueda, an assistant professor at Karolinska Institutet, the academic institution that ran the study.

“As there are growing calls from within the sport for greater measures to protect brain health, our study adds to the limited evidence-base.”

The “dose relationship”

While the academics differed on CTE risk calculations, both the Swedish and Scottish studies made an interesting observation: goalkeepers were at the lowest risk.

Goalkeepers, unlike outfield players, rarely head the ball. Repeated head impacts are believed to be the root cause of CTE, as they cause hundreds of small lesions within the brain that impair its function over time.

“It has been hypothesized that repetitive mild head trauma sustained through heading the ball is the reason football players are at increased risk, and it could be that the difference in neurodegenerative disease risk between these two types of players supports this theory,” Ueda said.

Experts from the Boston University Hospital Brain Bank who have been leading the charge on raising awareness of CTE in sports are more confident.

“The cumulative exposure to these mild repetitive head impacts is what we believe leads the player to a risk for CTE,” Dr Mary Ann McKee told the American Academy of Neurology. “In fact, in all our studies, if we look at the number of concussions, it doesn’t relate to CTE or CTE severity.”

The Swedish and Scottish studies also did not control for length of each athlete’s career, a factor which American researchers have found to be highly significant.

From ice hockey, to American football, to rugby, to bobsledding, no sport appears safe from the medical impacts of head injuries.

While the major concern over exposure to repeated head trauma is that it can lead to increased risk of neurodegenerative disease in the late stages of life, some die much earlier.

The recent deaths of two prominent American football players – aged 38 and 33 – are just two examples. As of May 2022, McKee said the brain bank had studied the brains of three athletes that died under the age of 34, indicating they developed their ALS in their 20s.

One died in his late 20s and two in their early 30s. One was a high school football player, another was a college football player.

The last was a semi-pro soccer player.

Image Credits: Albinfo.