Hi TS, there should be no hazardous side effects when you wear earplugs to sleep on regular basis. The only potential issues down in the road is that you could have accumulated earwax build up down in the road as you habitually pushing in your earwax with the earplugs (same goes with earbuds, ear digging with cotton buds). It's quite a common for hearing aid users too as they are wearing ear pieces on daily basis.