GERD can be worse after going to bed because your body is no longer in an upright position, with gravity helping to keep the contents of your stomach down. When you lie down, it is easier for acid reflux to go back up the esophagus and stay there for longer. In addition, due to decreased swallowing at night, there is less pushing of acid reflux back into your stomach from swallowing actions. During deep sleep, you also make less saliva (which helps neutralize stomach acid).