Stomach trouble in the middle of the night is mainly caused by duodenal bullae, duodenal ulcers, and reflux esophagitis. When the mucosa of the gastrointestinal system is healthy, it is protected by the mucosa, so it is not attacked by stomach acid. However, once the protective barrier of the mucosa is damaged, mucosal inflammation and ulcers occur, stomach acid will more easily cause irritation to the stomach wall and induce symptoms of stomach discomfort. The secretion of stomach acid is uninterrupted, especially in the middle of the night when it is at its peak. Since there is no food in the stomach, stomach acid is discharged into the duodenum at high intensity, which can cause stomach pain once there is inflammation and ulcers on the duodenal mucosa. Some people will have reflux esophagitis disease, it is best to sleep with the pillow elevated. Once the pillow is too low when sleeping, it will cause the level of the cardia to be lower than the site of the stomach acid, when the stomach acid will be more likely to reflux into the esophagus, causing damage to the esophageal mucosa, and therefore inducing stomach upset in the middle of the night.