Sleeping at night to the right side on the cough may be related to postnasal drip syndrome, lung infection, gastroesophageal reflux, heart failure, pleural effusion. 1. Postnasal drip syndrome: most common in allergic rhinitis, chronic sinusitis patients, in addition to coughing, coughing up sputum is often accompanied by throat drip flu, throat itching discomfort or nasal congestion, runny nose, sneezing and other symptoms, change posture may also appear coughing. 2. Lung infection, is a more common cause, bacterial or viral infection leads to airway inflammation, combined with more secretions. Changing positions may irritate the airway mucosa, leading to coughing symptoms. 3. Gastroesophageal reflux (GERD). Changes in body position can also cause reflux of gastric juices from the stomach through the esophagus to the throat, resulting in an irritating dry cough, which is also a common cause. 4. Heart failure. Changes in body position can also affect the blood circulation of the heart, and patients with cardiac insufficiency can experience cardiac circulatory disorders after a change in body position, leading to coughing. 5. Pleural effusion, also a common cause, can compress the bronchial tubes and lung tissues when the fluid is tilted to one side, leading to coughing symptoms. The exact cause of the cough needs to be investigated and treated according to the doctor’s instructions.