If there are no accompanying symptoms, there is no need to worry too much about the heart rate of more than 40 times/minute during night sleep, but if there are signs of insufficient blood supply, you should consult a doctor as soon as possible. During nighttime sleep, the vagus nerve dominates and inhibits the heart, so the heart rate is slower at night than during the day. In general, if the patient does not appear chest tightness palpitations shortness of breath and other symptoms, the heart rate of 40 to 50 times / min do not need to be overly nervous, belong to the harmless sinus bradycardia, can occur in normal people. Generally women’s heart rate faster than men, children faster than adults, if the occurrence of myocardial, cerebral blood supply insufficiency manifestations such as chest tightness, chest pain, dizziness, blackouts, fainting, etc., can not be taken lightly, and should be checked as soon as possible 24-hour ambulatory electrocardiogram to monitor the sleep heart rate. If discomfort exists, it is recommended to consult a doctor as soon as possible to avoid delaying the condition.