The study involved 12 healthy, heterosexual couples aged between 18- and 29-years-old who spent four nights in a sleep laboratory. Scientists measured the quality of their sleep by documenting their brain and heart activity, breathing, blood oxygen content, muscle tension, and movements in their eyes and legs.
The participants were monitored both sleeping alone and together as a couple. To add another dimension to the study, the volunteers also filled out questionnaires about their relationship. Questions included whether their partner made them feel angry, and how significant they were to their lives which the team used as a measure of depth.
Sleeping as a couple was linked with 10 percent more, less fragmented and longer phases of REM sleep. This type of sleep has been linked to the regulation of emotions, emotional memory, creative problem solving, and social skills.
Having a partner nearby may make sleeping feel like a safe environment as opposed to sleeping alone, the authors wrote.
And couples who said their relationship was a significant aspect of their live were more likely to have synchronized sleep patterns, which suggests there is a positive association between these two factors, the team said.
Co-author Dr. Henning Johannes Drews of Germany’s Center for Integrative Psychiatry, told Newsweek in an email the study was limited because it was carried out in an unnatural lab setting, and the participants were young, healthy, heteorxual, childless, and with a history of sleeping together—making them relatively homogenous. Future studies should involve a more diverse range of volunteers in naturalistic settings, said Henning.
The biggest challenge Hennig’s team faced when carrying out the study was measuring the couple’s sleep quality at the same time while enabling them to rest normally.
Henning said more research is needed to explore whether sleeping with a partner boosts a person’s mental health, memory, and creative problem-solving skills, which are known to benefit from REM sleep.
The study shines new light on a little understood topic. The vast majority of experimental sleep studies have looked at individuals, Henning said.
“Almost everything we know about sleep physiology refers to individual sleep,” he said. “That is somewhat surprising since sleep is an inherently social state with approximately 50 percent of the adult population in Western societies sharing the bed with a significant other.”
Henning said it is likely there is some evolutionary basis for the finding that partners appear to sleep better together.
“From an evolutionary perspective, sleep is definitely a social state. If you look at many primates, more traditional societies, or historic accounts for European societies, sleeping with others is very common,” Henning said. “Thus, for ages sleep and sociality were tied together and I think it is logical that by cutting that tie (e.g., by sleeping alone) one might find an effect on sleep.”
Asked for the take-home message, Henning said: “What people should not take from our study is that it is in any case better to sleep with a partner and that you cannot sleep well if you sleep alone.
“If your partner hinders you to fall asleep or disturbs your sleep, and you are much more relaxed if you sleep alone. That is probably the best sleeping arrangement for you.”
