Why do I have 'restless' legs?
By the faculty of Harvard Medical School for The Harvard Medical School Adviser

Q: I've seen TV ads for drugs to treat restless legs syndrome. What causes this problem?

A: Restless legs syndrome (RLS) is a surprisingly common disorder that causes odd, uncomfortable sensations in the legs during times of rest -- especially at night. People often describe it as a tingling, pricking, bubbling, tearing or burning sensation like "ants crawling up my legs" or "soda pop in my veins." Most often, the discomfort is centered deep inside the calves, but it can also occur in the thighs or feet. Various surveys suggest that RLS affects 5 percent to 25 percent of all adults.

RLS becomes more common as people get older, but it can begin surprisingly early in life. In early childhood, RLS is often misdiagnosed as "growing pains" or attention deficit disorder. RLS is more common in females than males.

In most cases, the cause is unknown. About 50 percent of patients have a strong family history of RLS, and researchers have linked the disorder to specific genetic abnormalities. Some cases of RLS are tied to other medical problems. Iron deficiency is the most common, which is why RLS often develops in regular blood donors. It has also been linked to diabetes, kidney disease, varicose veins, rheumatoid arthritis and Parkinson's disease, among other problems. When an underlying disease is linked to this syndrome, it's called secondary RLS. But in most cases, RLS strikes without rhyme or reason, and this form is known as primary RLS.

About 80 percent of people with RLS also have a related disorder, periodic limb movement disorder (PLMD). PLMD produces repetitive involuntary leg-muscle contractions: The legs jerk spasmodically ("Elvis legs") every 30 seconds or so during the nondreaming phases of sleep. Unlike the creepy discomfort of RLS, the jerking movements of PLMD occur during sleep. The patient doesn't know they are occurring -- but his or her bed partner certainly does.

The only way people with RLS can stop the ants crawling through their legs is to move about. They fidget, adjust their legs, and toss and turn in bed. The urge to move is irresistible. In severe RLS, patients have to get out of bed and pace the floor to get relief. The result is a truly bad night's sleep, causing morning headaches, fatigue, or exhaustion. Afternoon sleepiness, as well as poor concentration and trouble with memory and productivity are also common.

Unfortunately, many people with RLS are not diagnosed properly. The symptoms are often mistaken for insomnia, sleep apnea or other sleep disorders. Or they may be assumed to be arthritis, muscle cramps, peripheral artery disease, peripheral nerve disease or psychiatric disorders.

Some drugs may aggravate RLS. They include various antihistamines, some antidepressants and antinausea drugs like compazine. Calcium channel blockers (which are used for high blood pressure and angina) and metoclopramide (used for gastric disorders) may also worsen RLS. The same is true for nicotine, alcohol and caffeine.

Getting moderate exercise during the day may help calm your legs at night; walking is a fine example. Special leg-stretching exercises at bedtime may also help (see illustration). Some people find that cold showers are beneficial, but others prefer heat. Finally, some people with mild RLS may be able to get to sleep by simply massaging their calves or stretching their legs in bed.

Fortunately, only about a quarter of all people with RLS are affected seriously enough to require medical attention. Some patients with RLS respond well to a simple tranquilizer (such as diazepam, or Valium) at bedtime. Others do well with a pain reliever (such as propoxyphene, or Darvon). Certain antiseizure medications such as gabapentin (Neurontin) present another choice.

The FDA has approved two drugs, ropinirole (Requip) and pramipexole (Mirapex), specifically for RLS. Doctors often start with a low dose two hours before bedtime and gradually increase the dose if necessary. Side effects are uncommon, especially in the low doses used for RLS, but may include nausea, constipation, nasal stuffiness and fatigue.

RLS is an old problem, but new treatments can bring relief to most patients. If you have symptoms of RLS, check with your doctor. He or she may do a few simple blood tests, then take you off some medications or try you on others. One way or another, you should be able to move on to peaceful nights and productive days.

Copyright 2007 the President and Fellows of Harvard College. Developed by Harvard Health Publications (www.health.harvard.edu). Distributed by UFS. Submit questions to harvard_ adviser@hms.harvard. edu.