Numbness of hands and arms during sleep may be related to physiological factors such as incorrect sleeping posture, or it may be due to insufficient blood supply to the brain, cervical spondylosis and other reasons. 1. Physiological factors: in the process of sleeping, if the long time to maintain an improper sleeping posture, resulting in arms for a long time to be pressed, resulting in the pressure of the arm blood circulation to produce obstacles, may cause numbness of the hand, arm numbness. 2. Insufficient cerebral blood supply: when the human body is in a sleeping state, it will lead to slow blood flow, if there is cerebral atherosclerosis, due to the narrowing of the blood vessel lumen, resulting in insufficient blood supply to the brain, coupled with the slowing of the blood flow during rest, will aggravate the insufficient cerebral blood supply, which may lead to numbness of the hands and arms while sleeping, and may also be accompanied by dizziness, headache and so on. 3. cervical spondylosis: the disease can lead to patients with normal physiological curvature of the cervical spine changes, in the sleep if the pillow pillow height is not suitable, easy to lead to stiff neck muscles, tension, may compress the local blood vessels, resulting in the vertebral basilar artery blood supply is insufficient, may cause sleeping hand numbness, numbness of the arm. Sleeping hand numbness arm numbness, may also be caused by other reasons, by changing position, appropriate activities, if the symptoms still can not be relieved, it is recommended to seek medical advice as soon as possible.