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

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

In a recent study published in JAMA Network Open, researchers investigated how exposure to head trauma 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 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 condition that is primarily seen in contact sports but can only be diagnosed by examining the brain after death, characterized by distinct tubulin-associated unit (tau) protein pathology that differentiates it from other conditions.

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

Fewer cases of CTE have been reported in athletes playing ice hockey, but they have significant exposure to RHI from activities like fighting and checking. Athletes playing youth hockey in leagues that allow body checking are at a threefold higher risk for head injuries compared to those in leagues that do not allow it. Enforcers in the National Hockey League (NHL) who are known for fighting die an average of 10 earlier than non-enforcers.

A 2021 study found that 6 out of 11 athletes who played ice hockey at an elite level and died had CTE. Another study combining ice hockey and athletes in the Canadian Football League did not find a clear link between CTE and position played or the length of their careers, likely because of a limited sample size.

About the study

In this study, researchers tested if the duration of playing ice hockey and enforcer status are linked to higher CTE severity and risk. They aimed to assess if the severity of CTE is linked to dementia diagnosis as well as impairments in daily functioning among individuals with CTE.

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

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

Findings

The study included 77 donors, all of whom were White, with a median age of 51 years. Diagnosis of CTE was made for 42 donors, or 54.5% of the study population. Neurodegenerative disease accounted for 26.2% of deaths, while suicide accounted for 28.6%.

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

Nearly 82% of enforcers had CTE but had longer careers, more fights, and more penalty minutes per game on average than other players. Based on career length, nearly 96% of players who played for more than 23 years had CTE compared to slightly 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 contributing 34% to the odds of a CTE diagnosis and increasing the total tau burden by 0.037 standard deviations. No significant relationship was found with being an enforcer.

Conclusions

This study contributes to the evidence linking ice hockey to CTE and suggests that duration of play is a key factor in the risk for CTE. While these findings are indicative, two important limitations are the non-diverse sample and the fact that brain donation may not be representative of the overall population of male ice hockey players.