If numbness in the hands in sleep occurs occasionally, it is considered to be a symptom of local ischemia caused by poor blood circulation due to prolonged pressure on the arms as a result of poor sleeping posture. If the symptoms of numbness in the hands occur frequently, most of them are due to the herniated discs of cervical spondylosis compressing the nerves and causing numbness in the upper limbs. It may also be due to blood circulation slowing down during sleep at night, and cerebrovascular lesions such as cerebral thrombosis and cerebral infarction may also cause numbness in the hands, and most patients also have other neurological symptoms such as a deviation of the corners of the mouth to one side. Carpal tunnel syndrome and elbow tunnel syndrome are also common causes of numbness in the hands.