Arm numbness in side sleep is caused by compression of the brachial plexus nerve when sleeping on the side, resulting in nerve conduction impairment, which can cause numbness in the arm over time. So patients with this condition should change their sleeping position, do not sleep in the side position again, you can choose to sleep in the supine or prone position, so as to avoid nerve compression, so that the phenomenon of arm numbness does not occur. If the numbness in the arm lasts for a long time, you need to go to the hospital for an examination, and if the nerve is continuously stuck, you need to undergo surgery.