The relatively obvious and frequent coughing at night in patients with bronchitis is mainly caused by the following factors First, because of the inflammation of the bronchial tubes, the bronchial mucous membrane walls become significantly congested, edematous and exuding inflammatory secretions. The vagus nerve in the lungs is relatively excited at night, when the glands in the bronchial walls are highly secreted and accompanied by contractions and spasms of the smooth muscles of the airways to varying degrees, causing the lumen of the airways to narrow and the phlegm in them to increase, so that the symptoms of coughing are more frequent and more obvious at night. Second, when sleeping flat on the back at night, some of the secretions in the airway will reflux into the upper respiratory tract, which will aggravate the symptoms of coughing.