According to a study, couples who share the same bed sleep better. But just as for someone who can sleep alone and happy, this study does not apply to all couples.
Henning Johannes Drews, a researcher at the Center for Integrative Psychiatry in Germany, studied 12 heterosexual couples who spent 4 nights in a sleep lab. It measured the sleep of individuals together and separately using a technology that captured brain waves, movements, muscle tension and heart activity. Couples also completed questionnaires about their relationship.

According to the Drews team, couples who slept side by side had faster eye movement (REM), compared to those who slept separately. This is a good sign of sleep, which is related to the organization of memory, regulation of emotions, problem solving and social interactions.
 
Also, the better they listed their relationships in questionnaires, the more they were in sync when they slept side by side.
However, you do not necessarily have to have a partner to get a good night's sleep. Drews thinks some people are better off sleeping alone, regardless of their relationship status.

Quality of sleep in the couple

Why do some couples sleep better when they sleep together while others are happy to sleep in separate spaces?
Researchers think that sleeping in pairs increases 'REM', which can then reduce emotional stress and improve our interactions.
"An individual who is accustomed to sleeping with a partner in bed may experience a stress response when that partner is absent," Drews explained after reviewing the study abstract.
 
Interrupting Sleep
 
There are several factors that can interrupt our sleep. who speaks loudly in sleep can be a recipe for a bad night (or push for sleep divorce).
 
Although past research measured sleep movement between couples as a marker of poor sleep, many movements do not equate to a bad night’s sleep.
 
Drews noted more limb movements in couples sharing a bed, but that did not interrupt their sleep in his experiment.
 
Some of the people in the study were snoring and this did not affect the quality of 'REM' either.
According to another study, couples who get less than 7 hours of sleep a night are more likely to be hostile to each other. They may also experience stress-related inflammation, which can cause a host of different ailments.
More research needs to be done to understand positive co-sleeping between partners.


To sleep alone

Although ‘REM’ improved with a partner in Drews research, that does not mean you can not get good sleep if you sleep alone. Whether you are single or divorced, a good night's sleep is still possible for you.
"I think a person should follow the usual guidelines for sleep hygiene and creating an environment that promotes sleep," Drews said.
This includes avoiding stressful activities before bed, such as phone and TV screens an hour before bed, and keeping the area quiet and dark.