There are more and more complex reasons for coughing when lying down, and the common clinical reasons are as follows: 1. After lying down, the stomach and esophagus are at the same level, which can easily lead to reflux of gastric contents and stimulate the nerves in the throat to cause coughing. 2. Lung and throat diseases, commonly caused by cardiac insufficiency or serious lung infections, lead to pulmonary edema, tracheal or pharyngeal tumor stimulation, and gravity after lying down can lead to sputum or swelling to stimulate the 3.Patients with rhinitis or pharyngitis, reflux of nasal or pharyngeal secretions dripping down the trachea after lying down, stimulating the mucous membrane will cause coughing; pharyngitis will also cause reflux of sputum after lying down causing coughing. 4.If it does not occur during the day, coughing occurs after lying down at night considering the large temperature difference between day and night in the local area, the temperature drops at night easily stimulating the trachea causing coughing.