Medical Historians: We've Been Taught to Forget What We Used to Know about Head Injuries in Sports

In July, 2015, Stephen Casper, a medical historian, received a surprising e-mail from a team of lawyers. They were representing a group of retired hockey players who were suing the National Hockey League; their suit argued that the N.H.L. had failed to warn them about how routine head punches and jolts in hockey could put them at risk for degenerative brain damage. The lawyers, unusually, wanted to hire a historian. A form of dementia called chronic traumatic encephalopathy, or C.T.E., had recently been posthumously identified in dozens of former pro football and hockey players; diagnosable only through a brain autopsy, it was thought to be caused by concussions—injuries in which the brain is twisted or bumped against the inside of the skull—and by recurring subconcussive blows to the head. In the media, C.T.E. was being described as a shocking syndrome that had never been noticed in sports outside of boxing. In essence, the legal team wanted a historian to tell them what science had known about head trauma, and when.

Casper, a history professor at Clarkson University, in upstate New York, had majored in neuroscience and biochemistry, worked in a lab studying dementia in mice, and earned his Ph.D. in the history of medicine from University College London. His dissertation explored the emergence of neurology in the U.K.—a history that included the study of shell shock and head injury in the First and Second World Wars. Casper agreed to work for the hockey players. He turned his attention to a vast archive of scientific and medical papers going back more than a century. In constructing a time line of how knowledge on head injuries evolved from the eighteen-seventies onward, he drew on more than a thousand primary sources, including medical-journal articles, textbooks, and monographs.

Reading the research in chronological order was like listening to physicians and scientists conversing across time. The dialogue spanned several eras, each charting rising concerns about head injuries from different causes—from railroad and factory accidents to combat in the World Wars, and from crashes in newfangled automobiles to the rise of college and professional sports. Casper found that physicians had begun to worry about repeated head injuries as early as the eighteen-hundreds. In 1872, for example, the director of the West Riding Lunatic Asylum, in England, had warned that concussions, and especially repeated concussions, could result in mental infirmity and “moral delinquency.” Other asylum doctors called the condition “traumatic insanity” or “traumatic dementia.” From that time onward, discussion of the long-term effects of head injuries in varying contexts, including sports, surfaced again and again. Physicians recognized lasting sequelae of severe head trauma, and sometimes expressed concern about the consequences of milder head blows, too.

Today, C.T.E. is the subject of furious controversy. Some of the debate has been stoked by researchers affiliated with the sports industry, who argue that we still don’t know for sure that head blows in football, hockey, soccer, or rugby can lead, decades later, to the dramatic mood problems, the personality changes, and the cognitive deterioration associated with C.T.E. These experts maintain that, before we rethink our relationship with these sports, we need scientific inquiries that meet highly rigorous standards—including longitudinal studies that would take fifty to seventy years or more to complete. In the meantime, millions of children and high-school, college, and pro athletes would continue butting heads on the field.

Casper believes that the science was convincing enough long ago. “The scientific literature has been pointing basically in the same direction since the eighteen-nineties,” he told me. “Every generation has been doing more or less the same kind of studies, and every generation has been finding more or less the same kinds of effects.” His work suggests that, even as scientific inquiry continues, we know enough to intervene now, and have known it for decades. It also raises important questions about how, and how much, old knowledge should matter to us in the present. If Casper is right, then how did we forget what’s long been known? And when does scientific knowledge, however incomplete, compel us to change?