Whether a heart rate of 45 beats/minute is normal at night varies from person to person. For people who are in good health, a heart rate of 45 beats/minute at night is normal; however, for people whose normal heart rate is above 80 beats/minute, it may be caused by suffering from certain diseases. The heart rate of normal people is 60~100 beats/min. After sleeping at night, the heart rate can be lower because the body belongs to the resting state. For athletes and other people who exercise for a long time, because their heart muscle is more developed, the heart pumps blood more efficiently than ordinary people, so their low heart rate at night is normal. For ordinary people who usually have a high basal heart rate, the heart rate at night is usually 50~70 beats/minute which is more appropriate, if it is lower than 50 beats/minute, then it should be considered as myocardial injury, myocarditis and other diseases. Early detection and prevention. If there is a low heart rate, you should go to the regular hospital for examination and clear diagnosis.