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

https://wiki-triod.win/index.php/How_to_Protect_Hair_Extensions_Overnight_Without_Tangling:_A_Pro_Guide

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