If fasting gastric pH values are more acidic then why is it recommended to eat no more than three hours before bed time to prevent reflux. It seems at some point during sleep the stomach would become more acidic therefore make reflux worse.
Food only partially buffers the pH of stomach contents and acid is not the only esophageal irritant present in the stomach.
The goal, therefore, is to have as little as possible present in the stomach when lying down (supine) to reduce risk of gastro-esophageal reflux (GER) through the lower esophageal sphincter (LES) into the esophagus. Avoiding meals just before bed, especially fatty meals (which delay gastric emptying), may help in this regard perhaps by avoiding supine position while there is a low pH layer, formed in response to the meal, lying atop the stomach contents.
Weight loss and smoking cessation are frequently recommended to reduce GER symptoms, with some evidence to support this advice. Use of tobacco or alcohol may relax the LES and tends to be associated with GER symptoms, though trials of counseling to reduce their impact have not significantly reduced those symptoms (and another study).