Gravity and anatomy play a huge role in finding relief from nocturnal GERD symptoms. During the day, you are most likely standing or sitting up so when stomach acid escapes, gravity and saliva quickly return this potentially harmful substance to the stomach. Nights are a different story, even with the best bedtime rituals. And, depending on how you are sleeping, your esophagus can actually be below your stomach allowing acid to freely flow out and then just sit in your esophagus, lungs, throat, and sinuses.
Source: sleepscore