McKee, who can be the director of neuropathology for Veterans Affairs Boston, started finding out the brains of former NFL gamers 15 years in the past. She couldn’t consider what she noticed: large lesions within the crevices of the mind, dotted with irregular protein clusters. An enormous Packers fan, McKee has watched a whole lot of soccer video games. But, she recollects, till then, “it never occurred to me that they were damaging their brains, because you don’t see it on the field. They’ve got the helmets. They look invincible.”

Researchers now know extra about what is occurring to the mind beneath the helmet. The jostling of the mind tugs at neural tissue, putting cells and blood vessels below stress. Tau proteins, which stabilize the scaffolding that offers neurons their construction, fall off when a cell is burdened. These fallen proteins pile up contained in the cell, “a sort of toxic clump,” as McKee describes it. Eventually, the pileup overwhelms and kills the cell, leaving neurofibrillary tangles, which seem as ominous darkish smears below a microscope. These tangles, which also appear in Alzheimer’s disease, make it more durable for neurons to speak with one another, inflicting reminiscence issues.

Meanwhile, injured blood vessels compromise the sacred blood-brain barrier that usually protects delicate neural tissue from irritating molecules flowing by the remainder of the physique. The ensuing irritation causes irritation, which induces extra tau clumping, initiating a downward spiral of neurodegeneration.

To display screen the donated younger athletes’ brains for CTE, the researchers regarded for tau, in addition to indicators of larger-scale issues like irritation, hardening or deterioration of blood vessels, and modifications to white matter, which accommodates the connections between neurons. They additionally interviewed the donors’ family members to study extra about their habits and cognitive signs whereas they had been alive. All of them had skilled points like reminiscence loss, melancholy, and impulsive habits.

Of the 152 brains examined, 63 had been posthumously identified with CTE. The overwhelming majority had been nonetheless in early phases of neurodegeneration, however three of them—one belonging to a former NFL participant, one to a school soccer participant, and one to knowledgeable rugby participant—had reached the third of CTE’s 4 phases. Notably, one other mind with CTE belonged to a 28-year-old girls’s collegiate soccer participant—the primary case of its form.

The youth of those gamers additionally allowed the analysis crew to rule out getting older as the reason for the harm. Aging, in addition to hypertension, cardiac illness, and different neurodegenerative issues, can all harm mind tissue. But within the pattern used for the brand new examine, the entire athletes died between the ages of 13 and 29. “These are pristine, beautiful brains,” McKee says.

The proven fact that so lots of the donors’ households had observed temper and reminiscence modifications—no matter whether or not their baby was in the end identified with CTE—is likely to be an artifact of the examine’s pattern pool. Families had been merely extra more likely to donate to the mind financial institution if they’d observed uncommon habits of their baby. But McKee says this additionally means that among the signs skilled by these younger athletes are not at all times brought on by CTE, however should mirror the aftermath of head trauma. Chris Nowinski, a examine coauthor and CEO of the nonprofit Concussion Legacy Foundation, remembers fighting power signs after the concussion that ended his professional wrestling profession in his twenties. In instances like his, concussion-related issues like sleep impairments, or the difficulties of coming to phrases with life as an injured or retired athlete, are seemingly the basis explanation for the psychological well being points—not essentially tau pathology.