There is no scientific evidence to suggest that sleeping with a bra on is either healthy or unhealthy. It ultimately depends on personal preference and comfort.
Some women find it uncomfortable to wear a bra while sleeping, while others may find it provides support and prevents discomfort during the night. Wearing a bra that is too tight or constricting, however, could potentially lead to discomfort, irritation, or even affect breast tissue health.
It is generally recommended to wear a comfortable, well-fitting bra during the day and remove it before going to bed to allow the breast tissue to relax and breathe. Ultimately, it is important to listen to your body and do what feels most comfortable for you.