How Your Partner's Scent Affects Your Sleep

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Parents of young children may be familiar with an age-old trick: Leave your favorite sweatshirt or your own pillowcase with your sleep-resistant child at bedtime. The idea? They can smell your scent and be comforted, perhaps assuaging their urge to jump back out of bed and wake you up. If scent cues are important to children's sleep, might they also important to adults'?

Co-sleeping Builds Sleep Interdependence

Most coupled adults sleep in beds with their partner (Starvos, 2023). After an initial adjustment, sleeping in the presence of your partner can become routine and habitual. You're used to the rhythm of the night, their movements, their sounds. Providing that everyone is reasonably healthy and reasonably calm (and any children stay in their own beds), a "good night's sleep" feels like a self-assessment, one that has little to do with the other person.

But what happens when your partner goes away for a couple days? Suddenly you're trying to fall asleep and it feels different or strange. Is it the extra space? Is it the lack of noise or lack of movement? Or might it be a change in smells?

A Partner's Odor May Have a Calming Effect

A new study out of the University of British Columbia (Hofer & Chen, 2024) aimed to understand the role of a partner's scent on sleep among romantic partners. Their interest in olfactory cues during sleep makes sense, given recent research on how a romantic partner's scent can have a calming effect. Indeed, in a stressful situation, a romantic partner's body odor can lower someone's stress response and reduce their perceived distress (Granqvist et al., 2019). The "scent of security" (Granqvist et al., 2019) may trigger a parasympathetic response that lowers felt tension and increases calm.

If a partner's body odor can lower stress levels, might it also support a better night's sleep?

A Clever Experiment

Researchers recruited 155 participants with healthy sleep histories to participate in a sleep study (Hofer & Chen, 2024). The task was simple: Participants were asked to wear a wrist sleep tracker and sleep alone. They were also asked to replace their pillowcases with different specific t-shirts on each of four different nights.

What made the experiment work is that on two days the t-shirts were unscented or "control" (i.e., a stranger's scent) t-shirts, and on the other two days, the t-shirts had been previously worn by their romantic partner. Critically, the participant did not know which was which. Each morning, participants rated their perceived sleep quality.

Sleep Improves in the Presence of a Partner's Scent

Does a partner's scent really make a difference in sleep? Results from the study suggest it does. Results showed a surprising improvement in sleep between the unscented or control t-shirts nights and nights spent with t-shirts previously worn by their partners (Hofer & Chen, 2024). Fascinatingly, the degree to which a partner's scent benefited sleep aligned with the magnitude of taking melatonin. A partner's scent, it seems, is an effective sleep aid.

A partner's scent improved sleep efficiency, but people didn't notice (Hofer & Chen, 2024). In fact, their assessments of sleep quality were best predicted by whether they believed they had a t-shirt from a partner as a pillowcase. It seems our sense of sleep quality isn't well-aligned with metrics of actual sleep quality, which were, surprisingly, tied to partner scent cues.

A Simple Sleep Trick

This research offers an easy sleep improvement strategy to couples who experience regular separations but typically sleep in a shared bed. For the traveler, pack along a partner's worn sweatshirt; for the person at home, switch pillows and use your partner's for the night. By sleeping in the presence of a partner's scent, both may be on their way to a better night's sleep.

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