Did the San Francisco Giants win the World Series because they slept better?

A new study has found that professional baseball players' judgment significantly decreases as the season wears on, possibly because of the fatigue of playing nearly every day over the course of a seven-month season.

According to the study, published Thursday in the journal Sleep, baseball players are much more likely to swing at balls outside the strike zone in September than they are in the early parts of the season. According to lead researcher Scott Kutscher, a sleep and neurology professor at Vanderbilt University Medical Center, the decline in judgment "followed a linear pattern" from month-to-month and was consistent over the period of six seasons.

"We theorize that this decline is tied to fatigue that develops over the course of the season due to a combination of frequency of travel and paucity of days off," he said in a release statement.

Kutscher thought that players on teams located in the western part of the U.S. would show the most fatigue due to their frequent crossing through time zones. But the data suggest that the effect is consistent throughout the league.

"Teams on the east or west coast, with good or bad records, they all follow the same pattern of worsening plate discipline," he said. "This study suggests hitters always demonstrate the best judgment when at bat in the first month of the season."

Kutscher suggests that teams could try to let their players catch up on rest throughout the season in an attempt to gain a competitive advantage – a practice that some teams are already exercising. In 2012, U.S. News spoke with Chris Winter, a sleep expert hired by the San Francisco Giants to discuss sleep strategies with manager Bruce Bochy. Previous studies by Winter suggested that players who often reported feeling sleepy were more likely to have short careers in baseball.

At the time, Winter said that sleep "might be a new Moneyball situation" for teams that are smart enough to hire sleep experts.

"Steroids are now off the table, and teams are desperate for an advantage," he said. "Teams are now looking more at exercise, diet and health. Most teams now have dieticians, but the sleep thing is relatively new."

There's evidence that strategy may have worked. The Giants won the World Series in 2010 after speaking with Winter about sleep strategies. In 2012, they won again and, according to Kutscher, were one of the only teams whose plate discipline improved throughout the season.

"A team that recognizes this trend and takes steps to slow or reverse it – by enacting fatigue-mitigating strategies, especially in the middle and late season, for example – can gain a large competitive advantage over their opponent," Kutchser said. "This may have already occurred, as the San Francisco Giants – an outlier in the study in that their plate discipline improved during the 2012 season – went on to win the World Series."