Hands may swell during sleep due to dependent edema, which is an increase in fluid in a particular limb of the body. It could also be caused by heart medications, high blood pressure medications and even anti-inflammatories, according to Dr. Jose Monsivais. Circulation problems could also be a cause, potentially due to a lymphatic blockage.
There are a variety of ways to help with this swelling, depending upon its cause. One option is to drink plenty of fluids and to avoid excessive salt intake.
Hand swelling can also be caused by infections or "overuse or repeated motion," according to WebMD. If it occurs frequently, it can also be caused by an inflammatory process like arthritis.