TUESDAY, June 10 (HealthDay News) -- New research suggests that jet lag hampers the performances of continent-crossing pro baseball players but may boost the home field advantage of West Coast teams.

An analysis of 10 years of pro baseball scores found that teams were more likely to lose games if they were severely jet-lagged. The effect, however, wears off after a few days, and only a small number of games seemed to be affected.

Still, a lost game or two can make a huge difference in a season, said study lead author Dr. W. Christopher Winter. "There's clearly an advantage to being acclimated to your time zone, and you may be at a higher advantage in terms of winning games if you're living on the West Coast."

Winter, medical director of the Sleep Medicine Center at Martha Jefferson Hospital in Charlottesville, Va., had earlier studied games during the 2004 baseball season and found that jet lag hurt the performance of teams.

For the new study, Winter and his colleagues analyzed the scores of 24,133 baseball games with an eye toward how many time zones the teams had traveled through. It takes a day for a person's body to adjust to travel through a single time zone, he said.

Teams lost 60 percent of games in which they were at what the researchers called a three-hour disadvantage, meaning they needed three days for their bodies to catch up to their new location. They lost 52 percent of games in which they were at a one- or two-hour disadvantage.

The findings of the study, with funding from Major League Baseball, were to be released Tuesday at Sleep 2008, the annual meeting of the Associated Professional Sleep Societies, in Baltimore.

But if you're thinking the study might explain why your favorite team is playing poorly this season, think again. Players only rarely have to play games right after traveling across the country, so the most severe jet-lag effects appear to be limited, the study authors said.

In fact, for only about 16 to 20 times a season did teams have to travel three time zones and then promptly play a game, Winter said.

In a bit of a surprise, the researchers also found that teams traveling east to west suffered the most. Normally, people think west-to-east travel is most disruptive to their bodies.

Winter speculated that east-to-west travel may leave baseball players at less than their daily physical peak during games. "Their peak is not matching up to when they're being asked to perform," he said.

Dr. Robert Vorona, assistant professor of sleep medicine at Eastern Virginia Medical School, said jet lag disrupts the connection "between our internal rhythms and the external environment, because the body cannot shift that quickly."

However, an estimated one-third of people don't suffer from jet lag, so a team with more of these types of people could adapt more quickly to travel, he said.

Winter said it's not likely that baseball teams will ever get a week off between games, like professional football teams. But more recovery time after coast-to-coast trips would be helpful, he said.

As for the supposed advantage for West Coast teams, Winter said he wasn't sure why they haven't done better. "Why they're not winning more World Series, I don't know," he said. "Payroll, I guess."

More information

Learn more about jet lag from the U.S. Centers for Disease Control and Prevention.

SOURCES: W. Christopher Winter, M.D., medical director, Sleep Medicine Center, Martha Jefferson Hospital, Charlottesville, Va.; Robert Vorona, M.D., assistant professor, sleep medicine, Eastern Virginia Medical School, Norfolk; June 10, 2008, Sleep 2008, annual meeting of the Associated Professional Sleep Societies, Baltimore

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