After sleeping well at night, you still feel sleepy during the day. If the patient is an elderly person, he or she should consider chronic cerebral blood supply deficiency or cortical atherosclerotic encephalopathy, because the patient’s brain is in a chronic state of ischemia and hypoxia, and he or she will feel sleepy. Patients may also have high-fat and high-viscosity blood, which can slow down cerebral blood flow and lead to drowsiness, lack of mental clarity or drowsiness. If patients are obese, they may have sleep apnea or snoring at night, and although they feel that their sleep is good, they still have symptoms of lack of oxygen to the brain at night, and they will be sleepy during the day.