I'm thinking that the causation "may" go in the opposite direction: Couples are sleeping together because they are already healthy and compatible.
I love this:
In a 2010 study of 29 couples, women who had fewer negative interactions with their partners during the day slept better that night. For men, it was reversed: Better sleep led to fewer negative interactions with their partners the next day.And:
[O]n the days women said they had more positive interactions with their partners and fewer negative ones, the men slept better at night, too. "Women tend to drive the emotional content of the relationships," says Dr. Troxel, who co-wrote the study. "Husbands may take up a stronger signal" from wives.There seems to be a contradiction in there, but the conclusion is clear: Men need to get along with their wives.