Chronic traumatic encephalopathy risk in ice hockey increases with each year played

Study of 77 male hockey players found 96.4% of professionals had CTE, with risk and severity increasing with each year they played

From a recent study published in JAMA network openedResearchers have examined how exposure to head trauma resulting from playing ice hockey can increase the risk of encephalopathy, dementia, and functional status.

Their findings indicate that professional players show a high prevalence of encephalopathy and that there is a link between how long they played ice hockey (in years) and their risk of developing the condition.

Background

Chronic traumatic encephalopathy (CTE) is a brain disease caused by repetitive head impacts (RHIs). It is a neurodegenerative disorder that mainly occurs in contact sports, but can only be diagnosed by examination of the brain after death. This condition is characterized by distinct tubulin-associated unit protein (tau) pathology that distinguishes the disease from other conditions.

Previous research has shown clear relationships between contact sports played by individuals and their risk of CTE. For example, studies of athletes who play American football show that each additional year of playing increases the risk of developing CTE by 30%, and in severe cases up to 14%. Similar findings were observed in rugby players, with those who played longer having a higher risk of CTE.

Fewer cases of CTE have been reported in athletes who play ice hockey, but they are significantly exposed to RHI through activities such as fighting and checking. Athletes playing youth hockey in leagues that allow body checking have a three times higher risk of head injury compared to athletes in leagues that do not allow it. Enforcers in the National Hockey League (NHL) known for their fighting die on average ten earlier than non-enforcers.

A 2021 study found that 6 out of 11 athletes who played elite-level ice hockey and died had CTE. Another study combining ice hockey and athletes in the Canadian Football League found no clear association between CTE and the position played or the length of their career, likely due to the limited sample size.

About the study

In this study, researchers tested whether length of time playing ice hockey and enforcer status were associated with higher severity and risk of CTE. They wanted to assess whether the severity of CTE is associated with the diagnosis of dementia and with limitations in daily functioning in individuals with CTE.

Brain banks identified people who had donated their brains, focusing on male athletes who primarily played ice hockey, from youth to professional levels. The ethnicity and race of the donors were recorded. Informants provided data on the ages at which donors began and ended their hockey careers, years played, positions, and levels of play. It was also noted whether they practiced other contact sports.

Researchers also collected clinical data from medical records to assess daily functioning and diagnose dementia using specific criteria. They then performed neuropathological analyzes to measure phosphorylated tau (tau) in 11 brain regions. Statistical analyzes were used to analyze the relationship between years of playing hockey and cumulative tau load and diagnosis of CTE. Models were adjusted for position played, number of concussions, and age.

Findings

The study included 77 donors, all of whom were white, with an average age of 51 years. The diagnosis of CTE was made in 42 donors, or 54.5% of the study population. Neurodegenerative diseases were responsible for 26.2% of deaths, while suicide was responsible for 28.6%.

Of the 28 ice hockey players who had played professionally, 27 were diagnosed with CTE. NHL players had a 94.7% risk of CTE, while semi-professional level players showed a prevalence of 46.4%. Only 9.5% of younger players (e.g., high school players) were diagnosed with CTE.

Nearly 82% of enforcers had CTE, but on average had longer careers, more fights, and more penalty minutes per game than other players. Based on career length, nearly 96% of players who played more than 23 years had CTE, compared to just over 19% who played less than 13 years. The tau burden also increased with career length.

Researchers found evidence of a dose-response relationship, with each additional year spent playing the sport adding 34% to the chance of a CTE diagnosis and increasing the total tau burden by 0.037 standard deviations. No significant relationship was found with acting as an enforcer.

Conclusions

This study adds to the evidence linking ice hockey with CTE and suggests that playing time is a key factor in the risk of CTE. Although these findings are indicative, two important limitations are the undiversified sample and the fact that brain donation may not be representative of the overall population of male ice hockey players.