Whether or not the heart rate of 30 beats/minute during sleep is dangerous depends on the specific condition. If it is a transient bradycardia once in a while, the danger is low, and if it is a persistent bradycardia with long intervals, the danger is higher. If the heart rate is 30 beats per minute during sleep, an ambulatory electrocardiogram should be performed to find out the total heart rate. If the heart rate is occasional bradycardia, the heart rate will gradually increase after waking up, and there are no obvious symptoms, the condition is not serious. If the heart rate is sustained bradycardia, the heart rate remains slow when awake, and is accompanied by symptoms of weakness, dizziness, and chest tightness, the condition is relatively serious, which will have an impact on the patient’s cardiac function, and may even lead to serious myocardial ischemia, and the patient needs to go to the hospital to assess his or her risk. Patients with bradycardia should improve relevant examinations under the guidance of physicians and be treated according to medical advice.