SILVER SPRING, Md. — Most NFL games are played on Sunday afternoons, so it’s no surprise that many players prefer playing in the more exclusive primetime evening games that fans have come to know and love as Sunday and Monday Night Football. Now a new study finds there may be even more reason to covet the night games: players tend to play their best ball after the sun sets thanks to circadian rhythm advantages.

Primetime NFL games draw millions of viewers from across the United States and beyond. The success of Monday Night Football over the decades has given rise to Thursday Night Football and Sunday Night games during the NFL’s regular season. Researchers from the Walter Reed Army Institute of Research crunched game data and found that NFL players make fewer mental mistakes (resulting in penalties and turnovers) in games starting at 8 p.m. or 9 p.m. Eastern Time, compared to those that are played in the afternoon.

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Researchers compared the data to natural circadian sleep rhythms and found connections. “Based on what we know from decades of research on circadian rhythms of alertness and performance, we were expecting these data to explain why NFL teams win more games at night,” explains senior author and principal investigator Allison Brager, PhD, in a statement.

Essentially, one’s circadian rhythms produce greater alertness in night games, whereas afternoon contests showed a downswing in circadian-regulated alertness for players.

Using statistical analysis, Brager and her team created human performance response curves generated on biological time for points scored, yards gained, and turnovers for all 32 NFL teams in the 2013 season. These response curves compared the change in performance metrics relative to biological time, normalized to East Coast time. The models showed performance independent of home field advantage, talent level, and geography.

“We were not expecting that the largest influence on game outcomes at night compared to the afternoon would arise from mental errors in play and injury,” says Brager. “We grossly underestimated the impact that circadian rhythms have on risk for injury in athletes.”

Prior research established that West Coast teams generally perform better in primetime games than East Coast teams because of fewer injuries to linemen.

Brager presented the findings on June 3, 2017 in Baltimore at SLEEP 2018, the 32nd annual meeting of the Associated Professional Sleep Societies LLC.

The study was published in an online supplement of the journal Sleep.

About Ben Renner

Writer, editor, curator, and social media manager based in Denver, Colorado. View my writing at

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