Couples may get health benefits simply from sleeping in the same bed, a burgeoning field of study is showing. In fact, some scientists believe that sleeping with a partner may be a major reason why people with close relationships tend to be in better health and live longer.

The new research runs counter to studies that show women don't sleep as well with a partner and both men and women move around more when sleeping together. Other bed battles that interrupt couples' sleep include sheet-stealing and differing bedtimes and...