Chest pain at 4:00 a.m. may be due to respiratory disease or circulatory disease. 1. Respiratory diseases: it is due to increased pressure in the large airways or small airways leading to chest tightness and chest pain. Chest pain in the elderly is mainly due to bronchitis chronic obstructive pulmonary disease, the symptoms of which are mainly: cough, cough sputum, activity with wheezing, shortness of breath and other conditions. Young people are mostly due to chest pain caused by pneumonia, which can lead to chest pain waking up at four in the morning. 2. Circulatory system diseases: It is because of the transient dysfunction of the heart, resulting in insufficient blood perfusion, especially the myocardial oxygen demand is greater than the amount of oxygen supply, resulting in myocardial spasm, necrosis and its fibrosis. Mainly due to resting angina, coronary artery atherosclerosis, etc., can lead to 4:00 a.m. chest pain wake up. Persistent pain in the chest area, you should seek medical attention as soon as possible, combined with clinical treatment to avoid the development of the disease.