May 31, 2013 —
Science Daily/American Academy of Sleep Medicine
Two new studies show that fatigue may impair strike-zone judgment during the 162 game Major League Baseball season, and a MLB player's sleepiness can predict his longevity in the league.
One study found that MLB players' strike-zone judgment was worse in September than in April in 24 of 30 teams. When averaged across all teams, strike-zone judgment was significantly worse in September compared with April. The statistical model demonstrated strong predictive value through the season.
"Plate discipline -- as measured by a hitter's tendency to swing at pitches outside of the strike zone -- got progressively worse over the course of a Major League Baseball season, and this decline followed a linear pattern that could be predicted by data from the six previous seasons," said principal investigator Scott Kutscher, MD, assistant professor of sleep and neurology at Vanderbilt University Medical Center in Nashville, Tenn. "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."
Another study found a significant and profound relationship between the sleepiness of a MLB player and his longevity in the league. As baseline self-reported scores of sleepiness on the Epworth Sleepiness Scale increased, the likelihood that a player would be in the league three seasons later decreased linearly. For example, 72 percent of players with a baseline ESS score of 5 were still in the league at the follow-up point, compared with only 39 percent of players with an ESS score of 10 and 14 percent of players with an ESS score of 15.
"We were shocked by how linear the relationship was," said principal investigator W. Christopher Winter, MD, medical director of the Martha Jefferson Hospital Sleep Medicine Center in Charlottesville, Va. "It is a great reminder that sleepiness impairs performance. From a sports perspective, this is incredibly important. What this study shows is that we can use the science of sleep to predict sports performance."
Winter added that teams easily could implement sleepiness screening as part of their player evaluation system. "I can envision simple questions about sleep being a part of the battery of tests professional organizations use to evaluate prospects," he said. He also noted that players and their teams could benefit tremendously if a sleep specialist diagnoses and treats the condition causing a player to experience excessive daytime sleepiness. "That player may suddenly become far more valuable," Winter said.