Men sleep at night old hard is not a disease, belong to the normal physiological phenomenon. With the increase of urine in the bladder during sleep at night, it will stimulate the erectile nerve bundle between the bladder and the prostate gland, which will cause men’s penile erection and increase in hardness, which are normal physiological phenomena, every normal adult male is present, there is no need to worry too much. At the same time the male erection is also related to its sexual function, generally better sexual function of the male erection is stronger, usually in the wake up soon after the morning erection will disappear. It is recommended that you get enough sleep, as staying up late will have an adverse effect on the sexual function of the human body. It is also recommended to have proper physical exercise, such as jogging, swimming, basketball and badminton. To summarize, if there is any discomfort, you should consult a doctor in time.