Constant friction from cotton pillowcases is a quiet cause of overnight...

https://zulu-wiki.win/index.php/The_Art_of_the_Slumber:_Master_Your_Textured_Hair_Routine_for_Morning_Perfection

Constant friction from cotton pillowcases is a quiet cause of overnight breakage. While switching to silk helps, styling your hair into a loose, low plait before bed is the most effective way to minimise tangles