When one or both arms seem to fall asleep, it can feel as if they are going numb, or as if a person has pins and needles. The medical term for this feeling is paresthesia. A variety of causes may be responsible. Some are benign, while others require treatment.
Causes of the arms falling asleep at night
Most people experience occasional, brief episodes of paresthesia.
Often, a person’s position is the cause. For example, the arm may fall asleep because a person is lying in a way that puts pressure on a nerve in the limb.
Cases of positional paresthesia are harmless and generally occur when a nerve is under sustained pressure. The sensation should go away after a person changes positions.
The following medical conditions can also cause paresthesia in the arms:
Carpal tunnel syndrome
Carpal tunnel syndrome is very common. It occurs when activities that involve repetitive finger motion, like typing or playing the piano, put too much pressure on the median nerve. This nerve runs the length of the arm and passes into the hand through the wrist.
The syndrome can cause pain and numbness in the arms and hands, but one of the first symptoms is paresthesia that occurs in the hands and wrists more frequently at night.
According to the Cleveland Clinic, symptoms are likely to occur at night because people often sleep with their wrists bent.
People have a greater risk of carpal tunnel syndrome if they:
have a job that involves repetitive hand motions, such as typing or operating machinery
are retaining fluid
People with diabetes have a risk of nerve damage, and the medical term for this complication is diabetic neuropathy.
It occurs when high levels of sugar and fats in the blood injure the nerve endings over time.
Diabetic neuropathy usually causes numbness and tingling in the feet and legs, though it can also affect the arms and hands.
Vitamin B deficiency
Vitamin B deficiencies can cause a variety of problems, including anemia and tingling in the extremities. It can be easy to mistake this tingling sensation for the arms falling asleep.
People at risk for vitamin B deficiencies include:
vegetarians and vegans
adults over 50 years old
people with certain digestive disorders, such as Celiac disease or inflammatory bowel disease (IBD)
Other causes of peripheral neuropathy
Peripheral neuropathy is nerve damage that affects extremities. Diabetic neuropathy is one type.
However, many other factors can cause nerve damage that results in a sensation of the arms, hands, legs, or feet falling asleep.
Other causes of peripheral neuropathy include:
some types of injury
alcohol use disorder, which was once called alcoholism
certain medications, such as chemotherapy drugs
bone marrow disorders
infections, including Lyme disease and HIV
tumors that press on certain nerves
According to the National Multiple Sclerosis Society in the U.S., numbness and tingling are often the first symptoms a person experiences.
These symptoms usually affect the face. However, depending on the location of the spinal lesions that occur with multiple sclerosis, a person may also feel numbness and tingling in the arms or legs.
Strokes and transient ischemic attacks can cause numbness and tingling in the arms.
A transient ischemic attack occurs when something temporarily blocks blood flow to the brain. The American Heart Association considers these attacks to be “warning strokes.”
Strokes and transient ischemic attacks can affect the functioning of the nerves, and they can cause changes in sensation, including paresthesia in the arms or legs, as well as heightened feelings of numbness or pain.
It may be possible to prevent the issues that cause paresthesia in the arms at night.
For example, a person may benefit from learning to sleep in a less restrictive position. If a person is at risk of carpal tunnel syndrome, it may help to wear a brace or do exercises.
If a vitamin B deficiency is causing the sensation of the arms falling asleep, a doctor can prescribe supplements or recommend changes to the diet.