The influence of sexual activity on sleep

The influence of sexual activity on sleep: A diary study. Carlotta Florentine Oesterling, Charmaine Borg, Elina Juhola, Marike Lancel. Journal of Sleep Research, January 16 2023. https://doi.org/10.1111/jsr.13814

Summary: Aiming to promote overall health and well-being through sleep, the present studies examine to what extent sexual activity serves as a behavioural mechanism to improve sleep. The relation between sexual activity, i.e., partnered sex and masturbation with or without orgasm, and subjective sleep latency and sleep quality is examined by means of a cross-sectional and a longitudinal (diary) study. Two hundred fifty-six male and female participants, mainly students, completed a pre-test set of questionnaires and, thereafter, a diary during 14 consecutive days. The cross-sectional study was analysed using analysis of covariance and demonstrated that both men and women perceive partnered sex and masturbation with orgasm to improve sleep latency and sleep quality, while sexual activity without orgasm is perceived to exert negative effects on these sleep parameters, most strongly by men. Accounting for the repeated measurements being nested within participants, the diary data were analysed using multilevel linear modelling (MLM). Separate models for subjective sleep latency and sleep quality were constructed, which included 2076 cases at level 1, nested within 159 participants at level 2. The analyses revealed that only partnered sex with orgasm was associated with a significantly reduced sleep latency (b = −0.08, p < 0.002) and increased sleep quality (b = 0.19, p < 0.046). Sexual activity without orgasm and masturbation with and without orgasm were not associated with changes in sleep. Further, no gender differences emerged. The present studies confirm and significantly substantiate findings indicating that sexual activity and intimacy may improve sleep and overall well-being in both men and women and serve as a directive for future research.

4 DISCUSSION

The present cross-sectional and longitudinal (diary) studies aimed to investigate whether specific sexual activities (i.e., partnered sex and masturbation with or without orgasm) affect subjective sleep latency and sleep quality. The cross-sectional study showed that partnered sex with orgasm as well as masturbation with orgasm are perceived to reduce sleep latency while increasing sleep quality in men and women. Both men and women found that partnered sex and masturbation without orgasm increased sleep latency and decreased sleep quality, albeit men perceived stronger negative effects. The longitudinal study yielded diverging results. Specifically, while partnered sex with orgasm significantly shortened sleep latency and improved sleep quality, masturbation with orgasm did not affect the respective sleep variables. The effects of partnered sex without orgasm and masturbation without orgasm did not have strong enough effects on sleep latency or sleep quality to be detectable in the present design. Although women indicated a higher average sleep quality than men, gender was not found to significantly moderate the relation between sexual activity and sleep.

The present results largely support the hypothesis that sexual activity with orgasm results in reduced subjective sleep latency and increased subjective sleep quality in both men and women. While both studies found significant effects of partnered sex, masturbation – though retrospectively perceived as sleep-promoting – did not exert detectable effects in the longitudinal study. As masturbation with orgasm was indeed perceived to effectively promote sleep when assessed in retrospect, the results may suggest that, in fact, both sex with a partner and masturbation impact sleep latency and sleep quality, while the effect of partnered sex may be stronger and thus more salient. This postulate aligns with findings by Brody and Krüger (2006), who have shown that orgasm following sexual intercourse results in a 400% higher post-coital prolactin surge than masturbation-induced orgasm. As prolactin promotes sleep and is part of a feedback loop communicating sexual satiety, the increased post-coital surge of prolactin may explain why partnered sex is often perceived as more satisfying than masturbation and why the sleep-facilitating effect of sexual activity with orgasm is more salient when a partner is involved, as also found by Pallesen et al. (2020) and Gallop et al. (2021).

The finding that both partnered sex and masturbation without orgasm yielded no – or even negative – effects on sleep point to the relevance of orgasm and its concomitant psychophysiological effects. As orgasm is established to increase the heart rate and blood pressure and results in the release of oxytocin and prolactin – hormones, both postulated to influence sleep (Brody & Krüger, 2006; Fekete et al., 2014; Gianotten et al., 2021; Lipschitz et al., 2015) – neuroendocrine changes following orgasm may contribute to the reduction in sleep latency and increase in sleep quality following partnered sex with orgasm. The present observations are in accordance with earlier findings by Pallesen et al. (2020). Although Lastella et al. (2019) found that sexual activity is also reported to affect sleep when orgasm is not taken into consideration, the percentage of men and women reporting improved sleep latency and sleep quality increased when specifically asked about sex with orgasm. Further, reported gender differences indicating that perceived effects of sex on sleep are stronger in men were non-apparent when orgasm was assessed and may therefore emanate from a gap in orgasm frequency between men and women. Therefore, the discrepancy in results may also stem from less nuanced wording of items applied by Lastella et al. (2019). In a more recent study, Sprajcer et al. (2022) found that orgasm frequency explained 3.1% of the variance in subjective sleep latency, as participants reporting an orgasm “every time” sexual activity occurs fell asleep on average 12 min faster than those who less frequently or never report orgasm.

Given that masturbation with orgasm did not produce significant changes in longitudinally assessed sleep, orgasm per se does not sufficiently explain the reduction of sleep latency and increased sleep quality following partnered sex with orgasm. Other factors accompanying partnered sex with orgasm may also contribute to its positive effects on sleep, such as the mere experience of intimacy with one's partner promoting couple bonding (Kruger & Hughes, 2011), well-being, and emotion regulation (Gianotten et al., 2021) and may thereby improve sleep. Germane to this, non-sexual touch and cuddling have been shown to have calming, sleep-promoting effects, especially for women (Dueren et al., 2022). Compared with masturbation, partnered sex is often associated with more intense and longer-lasting physical activity – resulting in a heightened relaxed state afterwards – which may explain why partnered sex without orgasm resulted in a borderline-significant effect on sleep quality in the diary study despite being reported significantly less frequently than partnered sex with orgasm (n = 85 vs. n = 173). Lastly, the psychological effects of relationship satisfaction, loving and feeling loved, as well as having a sense of belonging or security also warrant consideration and have been shown to impact sleep (Kent et al., 2015; Troxel et al., 2007). Sprajcer et al. (2022) found that individuals who are emotionally satisfied fall asleep on average 10–12 min faster than emotionally unsatisfied individuals, and that orgasm frequency and emotional satisfaction are higher if sexual activity occurrs with a long-term partner, compared with casual sexual relationships. These findings highlight the importance of considering emotional and relationship factors when deriving inferences on the effects of sexual activity on sleep. Anyhow, if penetration has occurred, the positive effects of intimacy on sleep may be undermined if women, and even more so men, do not achieve orgasm. Both women and men retrospectively reported negative effects of sexual activity without orgasm on sleep. This negative perception, although not supported by the longitudinal findings, may be attributed to adjuvant emotions such as frustration, dissatisfaction, uncomfortable bodily sensations resulting from sexual arousal without orgasm, or confounding events that prevented sexual activity from resulting in orgasm.

The hypothesised gender difference suggesting that the effects of sexual activity on sleep are stronger in men than in women was not supported, as changes in subjective sleep latency and sleep quality following partnered sex with orgasm did not differ between men and women. This finding corresponds to results of Kruger and Hughes (2011), who also did not find any gender differences in the influence of sexual activity on sleep, and of Lastella et al. (2019), who did not find a gender difference when sex with orgasm had occurred. The absence of gender differences in the sleep effects of sexual activity with orgasm may be due to comparable endocrine processes following orgasm in men and women (Georgiadis et al., 2009; Mah & Binik, 2002). The widely held notion that men fall asleep faster than women after sexual activity may have emanated from the existing gender gap in achieving orgasm, i.e., women are less likely to reach orgasm during heteronormative sexual activity than men (Blair et al., 2018). Case numbers of the present study corroborate this notion, as although the sample consists of more than twice as many women as men, men reported a higher number of occurrences of both partnered sex and masturbation with orgasm. While following heteronormative scripts, women tend to engage in sexual activities that frequently result in orgasm for men but less often for women (e.g., vaginal penetration only, which does not suffice to achieve orgasm for most women; Lloyd, 2022). Research has further shown that the male orgasm frequently signifies the end of sexual intercourse (Opperman et al., 2014), which decreases the opportunities to achieve an orgasm for women. Women might simply reach orgasm less often and, therefore, less frequently benefit from the sleep-promoting effects of orgasm, which, in turn, may explain why society and cross-sectional research relying on self-report data postulate that men fall asleep faster following sexual intercourse with orgasm.

4.1 Limitations and future directions

While the results of the present study underpin the positive effect of sexual activity on sleep, several aspects may limit the interpretability of the findings. The convenience sampling procedure that also made use of a university-student participant pool of a Dutch University possibly limits the generalisability of the results, as most of the participants are young adults from western countries. As the understanding of sexuality concepts varies greatly across cultures (Hall & Graham, 2012), using a more diverse, inclusive sample is encouraged in future replications to increase external validity. Furthermore, suggestive wording in the pre-test items and normative responding based on the general widespread opinion of the sleep effects of sexual activity possibly resulted in recall and acquiescence bias and might contribute to the variability in results between the cross-sectional and longitudinal analysis. The longitudinal study was a preliminary attempt to bring a more thorough and objective insight into the impact of sexual activity on sleep. Yet, the borderline-significant effect of sexual activity without orgasm on sleep quality warrants further investigation, as it may point to a possible effect in the population that was underpowered (power = 0.51) and not detectable due to a small number of cases of partnered sex without orgasm (n = 85), of which the majority (n = 71) was reported by women. Thereby, examining this effect with a higher number of cases may be valuable, especially for female samples in which sexual activity without orgasm is particularly frequent, compared with male samples.

Due to the purely observational nature of the present study, future research might benefit from investigating the relationship between partnered and solo sexual activity, genital responses, the endocrine processes possibly underlying the effect sex has on sleep, and the psychophysiological markers of sleep in an experimental setting, thereby furthering what has only been done by Brisette et al. (1985). Another pathway could be to use a multi-modal machine learning approach implementing wearable devices to detect whether subjective and objective relations of sex and sleep patterns correlate. Self-monitoring the beneficial effect of sexual activity on sleep may have positive psychological effects and promote self-awareness.

Future research may consider differences between the effects in hetero- and homosexual couples and non-binary individuals, which were underrepresented in the present sample, as well as the effects different types of sexual activity have on sleep. Further, it is important to highlight that, by reducing sexual activity to partnered sex and masturbation, the present study applied a comprehensive – but restricted – definition of sexual activity. This served the extension of previous research in order to establish an underlying relationship between sexual activity and sleep. For future research, it would be important to apply a more inclusive, integrative conceptualisation of sexual activity by including a wide variety of sexual practices. Moreover, circumstantial factors such as having a new-born or small children, which possibly require frequent night-time engagement, may also be considered in future work, as both sex and sleep endure significant challenges and changes following the birth of a child (Kahn et al., 2022).

4.2 Strengths and implications

As the first to build upon previously conducted cross-sectional studies while also including a longitudinal design, the present study corroborated and extended the evidence for a sleep-promoting effect of sexual activity on sleep. By conducting an analysis in which the data are not aggregated but analysed with respect to their nested structure using MLM, the present study offered the opportunity to clarify diverging results regarding gender differences, type of sexual activity (masturbation vs. partnered sex), and the role of orgasm appraised by prior research. Moreover, controlling for relevant covariates, especially alcohol consumption which appeared to obscure the relationship between sexual activity and sleep, was valuable in the present study and is recommended for future research. The 14-day duration of the diary study, that includes weekdays as well as weekends, demands increased commitment of participants and further increases the value of inferences.

By using a cross-sectional design resembling the study conducted by Pallesen et al. (2020), their main findings could be replicated. The present study shows that both men and women perceive sexual activity followed by orgasm to reduce sleep latency and increase sleep quality (Gallop Jr. et al., 2021; Lastella et al., 2019; Pallesen et al., 2020). The results of the diary study corroborate the finding that sexual activity improves sleep while highlighting the effect partnered sex has on sleep, compared with masturbation. The heightened effect of partnered sex may partly be explained by the increased neuroendocrine changes following intercourse-induced orgasm, in combination with the valuable effects of experiencing intimacy with one's partner. Penetration and sexual intercourse aligned to heteronormative scripts may not necessarily be required to experience the beneficial effects of sexual activity on sleep. This notion is supported by the borderline-significant effect of partnered sex without orgasm on sleep quality, which is frequently reported by women and shows that intimacy alone may be sufficient to experience positive effects on sleep.

The present discordance of results between the cross-sectional study measuring the perception of the effects and the longitudinal study measuring the actual experience underlines the importance of applying objective measures and prospective measures appraising the perceived effect to the concepts of interest, as the subjective experience of sleep was shown to be a strong predictor of physical and mental well-being and cross-sectional methods are prone to be influenced by expectations and norms surrounding sexuality. In general, the same heteronormative implications of sexuality that underlie the orgasm gap between women and men may influence conceptions about “normal” sexuality – thereby resulting in confounded popular notions, such as men falling asleep first following sexual intercourse. Therefore, culture-specific norms and beliefs surrounding sexuality warrant consideration when interpreting the results of subjective research on sexuality.

The outcomes of the present research have important implications for sleep- and sexual medicine, as they highlight the value of considering partnered sex, masturbation, orgasm, and intimacy as a means to promote good sleep. The establishment of a relationship between sexual activity and sleep serves as a directive for future research to identify possible underlying mechanisms, such as endocrine or social-psychological processes, and to attempt an establishment of the effect using objective measures.