A paper by Naoko and others has been published in Scientific Reports.
Title: Social rank and social environment combinedly affect REM sleep in mice.
Press Release: Social environment impacts sleep quality
A study in mice demonstrates that one’s position in a social hierarchy and their degree of isolation have a measurable impact on the quality of sleep for individual mice
（The University of Tokyo）https://www.u-tokyo.ac.jp/focus/en/press/z0508_00438.html