There are studies in humans and animals revealing that lack of adequate sleep may facilitate sexual arousal, including objectively measured erections

Costa, R. M. (2019). Sleep and Sexual Arousal: A Complex Relation. The Journal of Sexual Medicine, 16(6), 946. doi:10.1016/j.jsxm.2019.03.267

I congratulate Smith and colleagues for their study on the relations of sexual function and sleep quality in older people,1a topic that deserves great attention. Their findings in a large representative English sample are extremely interesting, but also intriguing. Compared with men with high sleep quality, men with moderate sleep quality had greater odds of having erectile difficulties, but men with low sleep quality did not. Moreover, compared with men who sleep 6e8hours, men who sleep>8 hours had greater odds of having difficulties attaining orgasm, but men who sleep<6 hours did not.1Ifwe think that longer and better sleep favors sexual function, as many studies suggest, these are intriguing findings. Smith and colleagues note that the “results indicate that the relationship between sleep problems and sexual dysfunction is not as simplistic as previously suggested (poorer qualitysleep = greater dysfunction)” (p. 431), especially when several confounds are controlled.1

In this letter, I call the attention to an often overlooked phenomenon in the research on the relations between sleep and sexual function. There are studies in humans and animals revealing that lack of adequate sleep may facilitate sexual arousal, including objectively measured erections. After sleep deprivation, men diagnosed with psychogenic erectile dysfunction improved their erections in response to erotica,2 and for both sexes, poorer subjective sleep quality over the past month correlated with self-reports of greater unstimulated sexual arousal, that is, arousal in the absence of external stimuli.3 This occurred especially among those with higher testosterone levels.3 Among men, awakenings during both rapid eye movement (REM) and non-REM sleep increased visual attention to pictures of women, as assessed by eye-tracker, but the non-REM sleep awakening also disturbed REM sleep,4 which makes likely that it is the specific inhibition of REM sleep that has enhancing effects on sexual arousal. This is confirmed by research showing that REM sleep deprivation stimulates spontaneous erections and ejaculations in rats.5 The potential of REM sleep deprivation for increasing sexual arousal might be due to increased dopaminergic transmission, and it may also occur in women.3 Shortage of REM sleep is a likely consequence of many sleep disturbances.

Plausibly, in many cases, this effect may be offset by tiredness, difficulties interacting with the partner, psychopathology that develops due to lack of appropriate sleep, and perhaps by lower testosterone levels,3 among other factors. However, its presence might account for the complexity of the relationship between sleep and sexual function, as noted by Smith and colleagues.1