Now, a study1 published today in Science Translational Medicine reveals that the protective shield known as the blood'brain barrier can be damaged and leaky decades after an athlete retires from sport. This persistent leakiness seems to trigger a long-lasting immune response that is closely tied to cognitive decline, the study finds. The work is a 'very important study that finds the disruption of the blood'brain barrier many years after head trauma', says Katerina Akassoglou, a neuroimmunologist at the Gladstone Institutes in San Francisco, California, who was not involved in the research. Part of the difficulty in studying the long-term effects of head trauma is that some neurodegenerative conditions, such as chronic traumatic encephalopathy (CTE), can be diagnosed only by examining neuronal tissue after death, says Matthew Campbell, a specialist in neurovascular genetics at Trinity College Dublin, who co-authored the paper. Campbell and his colleagues wanted to see whether they could spot warning signs in living athletes by looking at the blood'brain barrier, a dense layer of cells lining the blood vessels that supply the brain. This layer usually keeps harmful substances from leaking out of the blood and into brain tissue....

At the turn of the 20th century, a sporty American woman would have had relatively few arenas to test her skill: croquet, maybe, or archery, or basketball played gently in an ankle-length skirt. Public displays of aggression were almost universally condemned, and colliding was especially unsavory. To avoid it, women's-basketball competitions prohibited 'snatching' the ball until the 1960s. Although men's and women's sports generally follow the same fundamental objectives today'stealing the basketball is a smart tactic in anyone's game'physical contact in women's sports remains controversial. When Caitlin Clark and Angel Reese exchange elbows in the WNBA, outrage and concern inevitably follow. Meanwhile, NBA players sparring over the ball, or NHL players outright brawling, is typically treated as business as usual. And yet, girls seem to be more interested than ever in contact. Ice hockey, rugby, and football (of the tackle, seven-on-seven, and flag varieties) are all among the fastest-growing sports for teenage girls. And at American high schools last academic year, more girls played on teams for wrestling than field hockey, gymnastics, or dance....

With the door locked behind me, I pulled out my phone and downloaded the DraftKings betting app. I felt a certain thrill as I typed in my debit-card information and deposited $500. The first game of the NFL season was a few minutes away. Anything seemed possible. I am not, by temperament, a gambling man. As a suburban dad with four kids, a mortgage, and a minivan, I'm more likely to be found wrestling a toddler into a car seat than scouring moneylines or consulting betting touts. And as a practicing Mormon, I am prohibited from indulging in games of chance. Besides, I had always thought of gambling as a waste of time. This makes me an outlier among my generational peers: Since 2018, Americans have wagered more than half a trillion dollars on sports, and roughly half of men ages 18 to 49 have an active account with an online sportsbook. When I set out to report on the sports-betting industry'its explosive growth, its sudden cultural ubiquity, and what it's doing to America'my editors thought I should experience the phenomenon firsthand. Mindful of my religious constraints, they proposed a work-around: The Atlantic would stake me $10,000 to gamble with over the course of the upcoming NFL season. The magazine would cover any losses, and'to ensure my ongoing emotional investment'split any winnings with me, 50'50. Surely God would approve of such an arrangement, my editors reasoned, because I wouldn't be risking my own hard-earned money....

Today's questions all come from McKay Coppins's April cover story on sports betting, for which The Atlantic spotted him $10,000 so he could become a degenerate gambler. Parlay all three questions for an extra payout of satisfaction. And by the way, did you know that, although estimates vary a bit, only about 3 percent of sports bettors turn a profit in the long run' And to do so, they must win not 50.1 percent of their bets, McKay reports, but more than 52.5 percent to account for the cut that sportsbooks take....