Sleeping with the arm up mainly has the following benefits, first of all, the arm up can avoid sleeping with the arm pressure, so as to avoid the upper limb blood flow obstruction performance, such as part of the people due to sleep pressure to the arm may be localized pain, swelling, and in severe cases can cause localized distal necrosis. Secondly, sleeping on the arm can be very good protection of the shoulder joint, especially with frozen shoulder, can avoid shoulder joint cold. But sleeping on the arm has benefits and bad places, easy to cause local cold, especially at night when the temperature is low, long time arm exposure is easy to cause arm numbness, cold, and cause local pain and discomfort, often so easy to arthritis performance.