Restless legs syndrome (RLS) causes an unpleasant prickling or tingling in the legs, especially in the calves, that is relieved by moving or massaging them. This sensation creates a need to stretch or move the legs to get rid of these uncomfortable or painful feelings. As a result, a person may have difficulty falling asleep and staying asleep.

One or both legs may be affected. In some people, the sensations are also felt in the arms. These sensations can also occur with lying down or sitting for prolonged periods of time, such as while at a desk, riding in a car, or watching a movie.

Many people who have RLS also have brief limb movements during sleep, often with abrupt onset, occurring every 5 - 90 seconds. This condition, known as periodic limb movements in sleep (PLMS), can repeatedly awaken people who have RLS and reduce their total sleep time. Some people have PLMS but have no abnormal sensations in their legs while awake.

RLS affects 5 - 15 percent of Americans, and its prevalence increases with age. RLS occurs more often in women than men. One study found that RLS accounted for one-third of the insomnia seen in patients older than age 60. Children also can have RLS. This condition can be difficult to diagnose in children, and it often is confused with hyperactivity or “growing pains.”

RLS is often inherited. Pregnancy, kidney failure, and anemia related to iron or vitamin deficiency can trigger or worsen RLS symptoms.

Researchers suspect that these conditions cause insufficient iron that results in a lack of dopamine. The brain uses dopamine to control limb movements. Doctors usually can diagnose RLS by patients’ symptoms and a telltale worsening of symptoms at night or while at rest. Some doctors may order a blood test for iron, although many people who have RLS have normal levels of iron in their blood but abnormal levels in the fluid that bathes their brain.

Doctors may also ask people who have RLS to spend a night in a sleep lab where they are monitored to rule out other sleep disorders and to document the excessive limb movements.

RLS is a treatable but not curable condition. Dramatic improvements are seen quickly when patients are given dopamine-like drugs.

Alternatively, people who have milder cases may be treated successfully with sedatives or by behavioral strategies. These strategies include stretching, taking a hot bath, or massaging the legs before bedtime. Avoiding caffeinated beverages can also help reduce symptoms.

If iron or vitamin deficiency underlies RLS, symptoms may improve with prescribed iron, vitamin B12, or folate supplements.

Some people may require anticonvulsant medications to stem the creeping and crawling sensations in their limbs. Others who have severe symptoms may need to be treated with pain relievers, such as codeine or morphine, or a combination of drug treatments.