Gravity

Acid reflux is a regurgitation of liquid (most often acid) from the stomach that begins to back up into the esophagus. It is more difficult for this liquid to come back up when sitting upright or standing. When lying down, the acid is more likely to remain in the esophagus, causing reflux in the morning to be worse until the body is upright again for a period of time.

Digestion

There are a number of things that aid in digestion. The act of swallowing as well as the production of saliva keep the digestive system moving. This occurs during waking activities like chewing and speaking. During sleep, neither occurs. The acid remains in the esophagus longer, causing heartburn and acid reflux when wakening.

Medication

There are two ways in which medication causes acid reflux to be worse in the morning. Certain medications taken at night–anti-inflammatories, sedatives, muscle relaxers, anti-depressants–can relax the lower sphincter and cause the regurgitation during the night, leading to more morning acid reflux. In addition, the medications taken to help acid reflux (antacids, proton pump inhibitors or H2 antagonists) are taken before bedtime and often just before dinner. This leaves a long stretch for the medication to stop working before a morning dose is taken.

Evening Meals and Drinks

During the day, our bodies have a chance to digest everything consumed while going about our daily routine in an upright position. At night, the body does not have as long to digest before going into a horizontal position. For those with acid reflux disease, this is especially problematic. Acidic (citrus, tomato), greasy or spicy foods, caffeine and alcohol all cause problems for those with reflux disease. Lying down at night after eating them can contribute to more severe acid reflux in the morning.