For a better time in the sack, hit the sack. That's the implication of a new study which found young women were more likely to desire sex – and have it – if they slept longer the previous night.
Women who got an extra hour of sleep were 14 per cent more likely to have sex with their partner the next day, according to findings published in the peer-reviewed Journal of Sexual Medicine on Monday.
And women who usually slept for longer reported better genital arousal than those whose average nightly shut-eye was shorter, the study reported.
This did not necessarily mean "the more sleep the better", lead author David Kalmbach said. Rather, maintaining a healthy amount of nightly rest was important to sexual health.
"These findings indicate that insufficient sleep can decrease sexual desire and arousal for women," Dr Kalmbach said.
"I think the take-home message should not be that more sleep is better, but that it is important to allow ourselves to obtain the sleep that our mind and body needs."
The study asked 171 female college students to complete a daily, web-based questionnaire on their sexual mood, sexual function and sleeping patterns, over a 14 days. The authors said they controlled for other factors that can influence sexual desire, such as wellbeing, menstruation and use of oral contraceptives.
The average age of the participants was 20, and 50 per cent had a "significant other". The average nightly sleep duration among the participants was seven hours and 22 minutes, while almost 20 per cent of the surveyed women reported clinically significant levels of "sexual distress".
In a quirk that surprised researchers, women experienced better vaginal lubrication and arousal the day after a shorter night's sleep. And yet, women with longer average sleep duration reported better genital arousal than those with shorter average sleep duration.
The authors said these findings were not mutually exclusive – it was likely, they suggested, that a single night of short sleep could boost libido whereas chronic sleep deprivation would have the opposite effect.
"Women with chronically insufficient sleep may be at greater risk for genital arousal difficulties, though one night of sleep loss appears to lead to short-term improvement in genital arousal the following day," the paper concluded.
The authors also noted the limitations of the participants' subjective reporting and recommended further research. But the study echoes previous findings – such as a 2011 paper which found men with poor and interrupted sleep patterns had lower levels of testosterone, resulting in decreased libido.
The better news for men is that watching pornography may actually aid sexual arousal. In a separate new study, researchers at Concordia College and the University of California found that men who watched porn regularly were more responsive when exposed to sexual stimuli. They also found no evidence that viewing porn led to erectile dysfunction, as has been argued by some commentators and doctors.
"Many clinicians claim that watching erotica makes men unable to respond sexually to 'normal' sexual situations with a partner. That was not the case in our sample," said Nicole Prause, who co-conducted the study, published in the online peer-reviewed journal Sexual Medicine this month.
Regular porn viewers responded "more strongly" to the "very vanilla erotica" shown to the study's participants than those who did not watch porn, Ms Prause said.
The data was collected from 280 male volunteers, 127 of whom had a steady partner.
