TORONTO -- The smell of a romantic partner is enough to improve quality of sleep, according to a new psychology study.
Researchers at the University of British Columbia found that study participants who were exposed to their partner鈥檚 scent overnight experienced better sleep quality, even though their partner was not physically present.
鈥淥ur participants had an average sleep efficiency improvement of more than two per cent,鈥� said Marlise Hofer, the study鈥檚 lead author and a graduate student in the UBC Department of Psychology.
鈥淲e saw an effect similar in size to what has been reported from taking oral melatonin supplements, often used as a sleep aid.鈥�
The study analyzed sleep data from 155 people who were given two identical-looking T-shirts to use as pillowcases: one had been worn by their romantic partner and the other had been worn by a stranger or was clean.
鈥淥ne of the most surprising findings is how a romantic partner鈥檚 scent can improve sleep quality even outside of our conscious awareness,鈥� said Frances Chen, the study鈥檚 senior author and associate professor in the UBC department of psychology.
Study participants weren鈥檛 told which T-shirt was which and spent two consecutive nights sleeping with each one. Each morning, they completed a survey about how well-rested they felt.
Their sleep quality was also measured using an actigraph sleep watch that monitored their movements throughout the night.
Participants reported feeling more well-rested on the nights when they believed they were sleeping with their partner鈥檚 scent. This was backed up by the sleep watch data, which indicated that sleep improved when participants were actually exposed to their partner鈥檚 scent.
鈥淭he sleep watch data showed that participants experienced less tossing and turning when exposed to their partners鈥� scent, even if they weren鈥檛 aware of whose scent they were smelling,鈥� Chen added.
The researchers said the physical presence of a long-term partner is associated with positive health outcomes such as a sense of safety, calm and relaxation, which in turn leads to better sleep.
By signalling recent physical proximity, the mere scent of a partner may have similar benefits, the researchers said.
Hofer said the research could pave the way for future work to improve sleep, such as bringing a partner鈥檚 shirt when travelling alone.
The researchers are now recruiting participants for a pilot study to investigate whether the scent of parents can improve their baby鈥檚 sleep quality.
