Dennis Frenkel's most recent concussion was so severe that he spent two weeks at home unable to do much of anything. His head hurt so badly that over-the-counter medication didn't touch it, he vomited twice, and his mother finally told him it was time to stop. He quit hockey for good after a series of concussions piled up, ending years with the Cougars youth hockey club in Cupertino.
Frenkel, now a junior at Gunn High School in Palo Alto, is one of several Bay Area athletes and coaches grappling with mounting evidence that head injuries from high-contact sports like football and hockey can cause brain damage later in life, according to The East Bay Times. “It meant everything to me,” Frenkel said of hockey, but he has come to believe he played too long and that continuing wasn't worth it.
A Junior's Decision to Walk Away
Frenkel played with the California Cougars youth ice hockey club as recently as December 2024, according to the outlet's reporting. The final concussion, and the two weeks it cost him, became the breaking point. “I was at home for two weeks because it was so severe. I quite literally couldn't do anything,” he said, describing how his head “hurt like crazy” even after taking medication.
His experience sits against a backdrop of research on chronic traumatic encephalopathy, or CTE, a degenerative brain disease that can currently be diagnosed only through neuropathological evaluation after death, leaving its incidence among younger athletes unestablished, per a study published in BMJ. That same study examined 1,712 former NFL players who died between 2008 and 2021, of whom 338 donated their brains for evaluation — and 315, or 93.2%, were diagnosed with CTE. Stage IV CTE among those donors was linked to clinician-diagnosed dementia, with a risk ratio of 1.44, the study found.
Uncertainty Clouds the Numbers
The BMJ researchers were careful to note that the 93.2% figure describes only the brains that were actually donated and studied, not the broader population of former players. Estimated CTE prevalence at death across all 1,712 former players in the study ranged much more widely, from 18.5% to 98.7%; narrowing to 2016 through 2021, when brain donation was most frequent, the range was 24.5% to 97.7%, according to the same BMJ findings. A Boston University researcher involved in related work on the topic said the relationship between amount of play and CTE risk appears fairly linear, which could mean higher prevalence for college and high school players too, per Boston University.
Hockey carries its own documented risk. A separate Boston University study found that the odds of CTE increased by 34% for every additional year a person played hockey. In a smaller study of 77 deceased male hockey players, CTE pathology turned up in 10% of the youth and high-school-aged players examined — 2 of 21 — though the same researchers cautioned those frequencies should not be read as a prevalence estimate for the broader population of young hockey players.
Coaches Try to Manage the Risk
At California High School in San Ramon, football coach Dan Calcagno has spent nearly 35 years on Bay Area sidelines and now limits player contact during weekday practices. He said coaches discuss concussion risks with players before each season begins, and when a head injury is suspected, trainers run through diagnostic sequences rather than leaving the call to him. “There are (diagnostic) sequences that we go through,” Calcagno said, adding that the final decision rests with the player, parents, or trainer. “I don't want to diagnose concussions,” he said.
California law requires that any student athlete suspected of sustaining a concussion or head injury be immediately removed from play for the remainder of that day, according to California legislative text. Calcagno said he still believes football is worth the risks — his own children play, including a son in college — and that he considers the sport a great experience even as he admits to feeling nervous about it. He estimated that about 95% of NFL players diagnosed with CTE would choose to play football again.
Participation Numbers Slide Statewide
Calcagno said concerns about long-term effects beginning with high school injuries have contributed to fewer students choosing to play football, and that a couple of high school programs have had to cancel outright because of low participation. That matches a broader trend: a CIF participation survey found 87,718 athletes played 11-man football statewide in the 2025-26 school year, a 4% drop from the prior year, even though it remains the most popular boys sport, per the Los Angeles Times.
Some schools have adjusted practice itself in response. Loyola High uses baseline testing of students' balance and brain function so results can be compared if a concussion is later suspected, the Times reported. Elsewhere, Brownsburg High School in Indiana has restructured practices to contain no tackling to the ground and rarely run longer than 90 minutes, according to The Washington Post. Federal data adds another layer to the concern: youth tackle football athletes experienced 15 times more head impacts than flag-football athletes during a practice or game, per the CDC.
Players Weigh Their Own Odds
Not every athlete is backing away. Arthur Tsagaan, a third-year football player at Gunn High School, said he isn't worried about developing CTE because hits at the high-school level are slower than those seen in the NFL or college, where impacts accumulate over time. He said measures are now in place to help athletes notice symptoms early, aiming to head off more severe consequences down the line.
That early-warning effort matters because CTE symptoms can resemble those of mental health disorders — irritability, mood changes, anger, and suicidal thoughts — making the disease difficult to distinguish from other struggles in a living person, since a definitive diagnosis still requires an examination of brain tissue after death. For Frenkel, the uncertainty wasn't worth testing further. Hockey, he said, meant everything to him — but he came to believe that continuing to play it did not.
