High blood pressure in the second half of the night is considered to be related to physiological factors such as staying up late and mental stress, and also to obstructive sleep apnea hypoventilation syndrome and heart failure. 1. Physiological factors: high blood pressure in the second half of the night may occur in people who stay up late, are nervous, or drink alcohol or coffee before going to bed. 2. Obstructive sleep apnea hypoventilation syndrome: the disease is related to the narrowing of the upper airway or the decrease of the ability to maintain the open function caused by nasal polyps and deviated nasal septum. It can cause high blood pressure in the second half of the night in some patients, and it is also easy to be accompanied by symptoms such as sleep snoring, dry mouth in the morning, drowsiness, lack of concentration, and increased nocturia. 3. Heart failure: the disease can also cause high blood pressure in the second half of the night in some patients. Heart failure is related to overloading of the heart and underloading of the ventricle, and patients will have shortness of breath, chest tightness, edema of both lower limbs, weakness, cyanosis and other symptoms. It is recommended that people with high blood pressure in the second half of the night seek medical examination in order to clarify the cause of the disease and then follow the doctor’s instructions for treatment.