A heartbeat of 30~40 at night while sleeping is abnormal. Normal people’s heart rate is low when they sleep, especially older people, but it is usually not as low as 30-40 beats/minute. A normal adult’s heart rate in a quiet state is usually between 60-100 beats/minute, with an average of 75 beats/minute. However, there are some people due to increased vagal excitability, such as some weak women or the elderly, athletes, etc. in the sleep state heart rate will be slower, but generally not lower than 50 beats / min. In this case, some pathologic conditions, such as atrioventricular block and sick sinus node syndrome, are often considered. In this case, it is necessary to do dynamic electrocardiography, echocardiography and other tests to see the overall heart rate variability, there are no other arrhythmia, and then clarify whether it is due to disease. To rule out specific diseases, such as hypothyroidism or medications, such as the beta-blocker metoprolol, which may cause bradycardia, a permanent pacemaker may be needed if there are no clear secondary causes of the slow heartbeat. Specific treatment needs to be prescribed by a physician.