Old sleepy reasons are the following: 1, due to various diseases caused by cerebral hypoxia, generally cerebral hypoxia after the cerebral nervous system will appear inhibitory state, at this time will feel the whole body is very fatigue, weakness, the old sleepy, sleepy. 2, it may be the night is not rested and tired due to many people due to the work of the pressure is relatively large or mental tension and other reasons caused by the night sleep is not good, during the day to sleep, Sleepy, this situation should be adjusted through life to alleviate. 3, the old sleepy may be the body suffers from some kind of disease, such as cerebrovascular disease can damage the brain nerves, will make people appear sleepy. In addition, if you suffer from hypothyroidism this kind of disease, will lead to the whole body metabolism is slow, will also make people feel tired and sleepy. There are also chronic diseases such as diabetes and high blood pressure, which can make people feel sleepy and mentally ill.