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BALTIMORE -- Sleepy men exercised poor judgment regarding whether a woman is a willing sex partner -- similar to errors made when drinking to excess, researchers reported here.

When men were deprived of sleep, the men's rating of a woman's sexual intent increased significantly from a score of 13.5 to 17.55 (P<0.05), said Jennifer Peszka, PhD, associate professor of psychology at Hendrix College in Conway, Ark.

However, there was no change in how the women perceived the men, even with the same amount of sleep deprivation, Peszka told MedPage Today at her poster presentation at the annual meeting of the Associated Professional Sleep Societies.

Action Points Note that this study was published as an abstract and presented at a conference. These data and conclusions should be considered to be preliminary until published in a peer-reviewed journal.

Sleep deprivation did not affect women's perceptions but it did lead to an increase in men's perception of women's interest in and intent to have sex.

"Our findings here are similar to those from studies using alcohol, which similarly inhibits the frontal lobe of the brain," said Peszka, the co-principal investigator in the study along with Jennifer Penner, PhD, also an associate professor of psychology at Hendrix. Sleep deprivation is known to impair frontal lobe functioning, which negatively affects decision-making and increases risk-taking, Peszka said.

"Sleep deprivation could have unexpected effects on perceptual experiences related to dating and mating that could lead people to engage in sexual decisions that they might otherwise not when well-rested," she said.

The consequences of misconstruing a woman's interest can lead to serious problems, she said, including sexual harassment, unplanned pregnancy, contracting sexually transmitted diseases, and relationship conflicts.

The researchers recruited 60 college students for the study. They completed the Cross Sex Perception and Sex and Commitment Contrast psychological testing instruments before and after one night of sleep deprivation. Participants rated their level of agreement with a series of statements on seven-point Likert scales regarding sexual interest, sexual intent, commitment interest, and commitment aversion for themselves and men and women in general.

"Just as with alcohol, sleepy men are judging women and thinking they are more likely to want sex than they did when they were not sleepy," she said. "And just as in the studies that have used alcohol, we found that women were not affected by sleepiness in their perception of sex."

Because both sleep deprivation and alcohol impact the frontal lobe, "we had expectations that we would see the same thing," Peszka said.

David Mastin, PhD, professor of psychology at the University of Arkansas at Little Rock, suggested that men who drink at a bar and get sleepy may be reacting to a synergistic shot to the frontal lobe that can adversely affect their decision-making regarding a possible date or mate.

So why doesn't sleep deprivation impact women's decisions? "We really don't know," Peszka said. "The literature suggests that women are looking for different things when dating and mating, while men are always looking for sex.

"Because women are making bigger decisions that are more important to them, they may be making instinctive decisions rather than cognitive ones. But this is just a hypothesis."

"This study and others illustrate why it is not a good idea to make decisions when you are sleepy," Michael Grandner, PhD, instructor in psychiatry at the Perelman School of Medicine at the University of Pennsylvania in Philadelphia, told MedPage Today.

"When people are sleepy they have a lack of control in the ability to make good decisions, and this study appears to illustrate that point," he said.