Bookmakers have long factored home-field advantage into a baseball team's odds of winning, but a new study suggests that jet lag could wipe it out.
Researchers analyzed more than 46,000 Major League Baseball games played over the course of 20 years - from 1992 until 2011 - and saw the home-field advantage disappear when the home team traveled two time zones east and the away team visited from the same time zone.
"We all know intuitively from experience what it means to be jet-lagged," said senior researcher Dr. Ravi Allada, a circadian rhythms expert and neurobiology professor at Northwestern University in Evanston, Illinois.
"We all know it will impact our own performance," he said in a phone interview. "I think we showed very specifically what it is."
Pitchers - on both home and away teams - gave up more home runs when they presumably suffered jet lag as a result of traveling through two time zones, the researchers report in the Proceedings of the National Academy of Sciences.
Jet-lagged home-team pitchers allowed enough home runs to negate their home-field advantage, Allada said.
Prior studies have shown that eastward travel is more likely to desynchronize internal clocks than westward travel, the authors write. The new study confirmed that eastward travel was more likely to alter baseball players' performance.
Surprisingly, when both teams were jet-lagged, the offense for eastbound jet-lagged home teams suffered more than the offense of jet-lagged away teams, the study showed. The eastward-traveling home teams ran and stole fewer bases, batted in fewer doubles and triples and hit more double plays, the analysis found.
Allada hypothesized that traveling players may follow stricter schedules, which could help them recover faster from jet lag, than players on the home team. Baseball players also may have more responsibilities and obligations when they are at home and less time to adjust their clocks, he said.
When games are two time zones or more away, coaches should consider having their starting pitchers fly a day or two before games to adjust their clocks to the local environment, Allada said.
The same advice could apply to athletes on other sports teams as well as to travelers in other professions, including military pilots, Allada said. A Defense Advanced Research Projects Agency grant partly funded the study.
After staying up late and sleeping in over the weekend, adolescents face similar disruptions to their circadian rhythms on Monday mornings if they must rise at 6 a.m. and take tests at 8 a.m., said Dr. Asha Singh, medical director of the Sleep Disorder Program at Oregon Health and Science University in Portland.
People who work night and graveyard shifts also must adjust their clocks. Exposing themselves to bright lights and taking supplements containing melatonin, a naturally secreted hormone, a few hours before bedtime can help, Singh said in a phone interview. She was not involved with the new study.
The new research replicates what she's seen in patients in the sleep lab, she said.
Eating at regular intervals and exercising earlier in the day also can help regulate circadian rhythms, Singh said.
Nighttime exercise delays the release of melatonin, which is necessary to go to sleep. "You want to make sure you're not asking your players to do that," she said.
Light and genetics are the most powerful factors, she said.
"It's genetic how easily you're able to shift," she said. "It's actually encoded in your DNA, even in fruit flies."