Review strengthens evidence that repeated head impacts can cause CTE
Over the past 17 years, there has been a notable increase in scientific research into chronic traumatic encephalopathy (CTE), with researchers at the BU CTE Center leading the way. Although some sporting organizations such as the National Hockey League and World Rugby still claim their sports do not cause CTE, a new review of the evidence by the world’s leading CTE expert strengthens the argument that exposure to repetitive head impact (RHI) is the most important risk factor for the condition.
CTE became national news in the United States in 2007, but it was not until 2016 that the National Institute of Neurological Disorders and Stroke/National Institute of Biomedical Imaging and Bioengineering (NINDS-NIBIB) criteria for the neuropathological diagnosis of CTE were published. and they were refined in 2021. Rare, isolated case studies that reported abnormal findings or used unaccepted diagnostic criteria have been disproportionately emphasized to cast doubt on the link between RHI and CTE.
In a review article in the magazine Acta NeuropathologicaAnn McKee, MD, chief of neuropathology at VA Boston Healthcare System and director of the BU CTE Center, emphasizes that more than 600 CTE cases have now been published in the literature from multiple international research groups. And of the more than 600 cases, 97 percent have confirmed exposure to RHI, mainly through contact and collision sports. CTE has been diagnosed in amateur and professional athletes, including athletes from American, Canadian and Australian football, rugby union, rugby league, soccer, ice hockey, bull riding, wrestling, mixed martial arts and boxing.
Additionally, the study authors revealed that in 82 percent (14 of 17) of alleged CTE cases that occurred without RHI, using current criteria, families were never asked what sports the deceased played.
According to the researchers, despite global efforts to find CTE in the absence of contact sports participation or exposure to RHI, it appears to be exceedingly rare, if it exists at all. “In community brain bank studies, CTE was seen in 0 to 3 percent of cases, and where information is available, positive cases were exposed to brain injury or RHI. In contrast, CTE is the most common diagnosis of neurodegenerative diseases in contact and collision athletes in brain banks around the world. A strong dose-response relationship is perhaps the strongest evidence that RHI causes CTE in athletes,” she added.
“The review presents the timeline for the development of neuropathological criteria for the diagnosis of CTE, begun nearly 100 years ago by pathologist Harrison Martland, who introduced the term ‘punch-drunk’ to describe a neurological condition in low-cost carriers, ” explains McKee. author of the study. The review chronologically describes the multiple studies conducted by independent, international groups examining diverse populations that have found CTE pathology from various sources in individuals with a history of RHI.”
CTE is characterized by a distinctive molecular structural configuration of p-tau fibrils that is different from the changes seen in aging, Alzheimer’s disease, or any other disease caused by tau protein.
Funding for this study was provided by the National Institute of Neurological Disorders and Stroke (U54NS115266; R01NS119651; U01 NS 086659), National Institute on Aging (P30AG13846; U19AG06875; R01AG062348; RF1AG057902; K01AG070326), Department of Veterans Affairs (10 1 BX002466, 101BX004613, BX004349), the Nick and Lynn Buoniconti Foundation, Andlinger Foundation, National Football League (NFL) and World Wrestling Entertainment (WWE) through unrestricted gifts, the Mac Parkman Foundation and the National Operating Committee on Safety for Sports Equipment (NOCSEA).
