Smelling Your Special Someone’s Shirt May Improve Your Sleep

"Our findings provide new evidence that merely sleeping with a partner's scent improves sleep efficiency. Our participants had an average sleep efficiency improvement of more than two per cent," said Marlise Hofer, the study's lead author and a graduate student in the UBC department of psychology. "We saw an effect similar in size to what has been reported from taking oral melatonin supplements—often used as a sleep aid."

As published in the journal Psychological Science sleep data was analyzed from 155 participants who were given 2 identical t-shirts to use as pillowcases, one of which had been worn by their romantic partner and the other was either clean or worn by a stranger. The previously worn t-shirts were worn for 24 hours while the person refrained from using deodorant and scented products, smoking, exercising and eating certain foods that can affect body odor, after wearing the t-shirts were frozen to preserve scent. 

Without being told which t-shirt was which the participants were given two t-shirts to place over their pillows to sleep on for two consecutive nights; after each night the participants completed a survey regarding how well rested they felt. Sleep quality was objectively measured using an actigraphy sleep watch that monitored their movements throughout the night, and at the end of the study participants guessed if the shirt they were sleeping with had been worn by their partner. 

Participants reported feeling more well rested after nights when they believed they were sleeping on the t-shirt that had been worn by their partner; regardless of their belief on scent exposure the data from the sleep watches indicates that their objective sleep improved when they were actually being exposed to their partner’s scent.

“One of the most surprising findings is how a romantic partner's scent can improve sleep quality even outside of our conscious awareness," said Frances Chen, the study's senior author and associate professor in the UBC department of psychology. "The sleep watch data showed that participants experienced less tossing and turning when exposed to their partners' scent, even if they weren't aware of whose scent they were smelling."

According to research the physical presence of a long term romantic partner is associated with positive health outcomes such as feelings of calm, safety, and relaxation which can lead to better sleep quality. The researchers suggest that by signalling recent physical proximity the mere scent of a partner may have similar benefits. 

This study may open opportunities for additional research to examine the efficacy of simple and effective methods to improve sleep, such as bringing a shirt or sweater that belongs to you special someone the next time you travel alone. 

Participants are currently being recruited for a pilot study to investigate whether the scent of parents can help to improve their infant’s sleep quality.