Can Time Zones Decide NFL Games?

A study looks at how circadian cycles affect NFL players
Illustration by Tane Williams

The National Football League, with its revenue sharing and salary caps, is obsessed with parity. But it can’t regularize everything—there’s the weather and Bill Belichick. And time zones: A paper from sleep researchers at Harvard Medical School, Stanford University, and the University of California at San Diego finds that football teams from the Pacific time zone have a pronounced advantage at home games when playing teams from the East.

The study, published in the December issue of Sleep, looks at 40 years of West-on-East NFL action, such as the San Francisco 49ers vs. the New York Giants, or the Oakland Raiders vs. the New England Patriots. The data were divided into evening and afternoon games and compared with the Vegas point spread to control for the sort of factors bookies take into account—home-field advantage, injuries, whether a game matters to a team’s playoff chances. In the evening, Pacific teams beat the spread twice as often as their East Coast opponents. “That just one piece of information could be that predictive over 40 years is a powerful piece of knowledge,” says Roger Smith, one of the authors and a clinical instructor at Harvard Medical School.

The East Coasters, he argues, were suffering from “circadian misalignment.” (He published an almost identical study in 1997 looking solely at Monday Night Football games, with similar results.) The advantage, the authors conclude, doesn’t spring from the West Coast offense or the gentle Pacific clime, but from the human circadian rhythm: the inevitable rise and fall of physical and cognitive performance levels over the course of each day. Some studies have shown several aspects of human performance peak in the late afternoon and reach their low in the very early morning, at about 3 a.m. The researchers posit that the West Coast teams outperformed their opponents at away games because they were nearer to their peak. The East Coast teams were closer to their bedtimes—and their 3 a.m. nadir. But all is not lost for East Coast athletes, Smith says. The body’s internal clock is malleable, so the effect he found can be mitigated if players take a few days to acclimatize to the time zone in which they’ll be playing.

The results are intriguing, but the sample size is small; few NFL games are played in the evening, and there are only four teams on the West Coast. But if there’s one finding that researchers in the nascent field of chronobiology (the study of the body’s internal clock) agree on, it’s that circadian rhythms are different for everyone. Certain people really are morning people, while others perform better in the evening—sleep researchers call them larks and owls. And it would be beneficial to match our work schedules, to the extent that we can, to our tendencies. Amita Sehgal, a neuroscientist at the University of Pennsylvania, points out that some do their best work not during the traditional workday but starting in the early evening. “You can certainly make the case,” she says, “that people should be assigned to jobs based on their rhythms.”

As for the NFL results, if Smith and his co-authors have found a hidden advantage, the only way for professional sports leagues to stamp it out would be to schedule all games in the midafternoon or ensure that teams from the most disparate time zones don’t play each other in the evening. Of the remaining regular-season games, only one fits Smith’s conditions: On Dec. 23, the Atlanta Falcons will play the 49ers in San Francisco at 8:40 p.m. East Coast time. For you bright-eyed folks in California, that’s 5:40.

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