Last updated: Apr 29, 2008
pregnant-woman-legs-bed
Pregnancy can bring on temporary RLS symptoms, especially after week 20.
(VEER)
For years, doctors have actually known more about how to treat restless legs syndrome (RLS) than about what causes it. They've discovered that symptoms sometimes improve with medications that trigger the production of dopamine, a chemical in the brain that regulates movement and feelings of pleasure. But there is some evidence that dopamine is only one of many factors in causing RLS.


It's suspected that RLS acts up especially at night because dopamine levels follow the body's circadian rhythm, and decrease as the body winds down for sleep, says Charlene Gamaldo, MD, assistant professor of neurology at Johns Hopkins University in Baltimore.

Scientists also suspect that the abnormal levels of dopamine that can trigger RLS in some people may be caused by low iron in the blood. But even then, there's often not a good explanation as to why one person experiences symptoms and another doesn't. Whether or not there's an underlying condition that contributes to RLS divides it into two types: primary and secondary.

Primary RLS
When all outside factors and other conditions have been ruled out as a cause for RLS symptoms, the condition can be classified as primary RLS. It is usually found in early onset cases, before the ages of 35 to 45, when there are no other identifiable causes. It has long been suspected that primary RLS can be hereditary, and in 2007, scientists at Emory University discovered a gene variant that more than doubles a person's risk of developing RLS.

Mimi Gauthier, a movie set decorator in New Orleans, recalls her father's battle with RLS: He always had to shake out his legs repeatedly before he could sit in his lounge chair and snooze, and he napped frequently during the day. Gauthier's own legs started bothering her at age 6, and today at 47 she suffers from severe RLS that leaves her constantly exhausted and sleep deprived.

Secondary RLS
Before you consider drug treatment for RLS, it's important to make sure your condition is not aggravated by something that can be cured or controlled on its own. Pregnancy sometimes causes temporary symptoms which usually disappear slightly before or after giving birth.

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Other conditions that have been linked to RLS include diabetes, Parkinson's disease, rheumatoid arthritis, and kidney failure. Iron deficiency, or anemia, can also be a cause (though it is not that common), and is usually treated with dietary supplements.

"When a patient comes in with RLS symptoms, the first thing we do is check iron levels," says Dr. Gamaldo. "Sometimes restless legs can be a blessing in disguise, because they alert us to underlying medical conditions. If a seemingly healthy man under 50 turns out to be iron-deficient, we consider the causes: blood loss, colon polyp, colon cancer. We might catch a previously undiagnosed problem."

Factors that aggravate RLS
Sleep deprivation can make subtle RLS symptoms much worse, so sleep specialists often find that when a separate cause of sleep loss is treated—insomnia with medication, or sleep apnea with continuous positive airway pressure (CPAP) therapy—patients report that their RLS improves as well.

Another drug you're taking can trigger RLS as well, so if you've noticed restless legs while on the course of any medication, mention it to your doctor. Here are some drugs that can affect RLS.
• Calcium-channel blockers(blood pressure and heart medications)
• Reglan (metoclopramide), a heartburn medication
• Anti-nausea medications
• Some cold and allergy medications
• Major tranquilizers (including haloperidol and phenothiazines)
• Phenytoin (an anti-seizure medication)
Antidepressants

For people who are predisposed to RLS, substances such as caffeine, alcohol, and tobacco may also trigger symptoms. If you are experiencing restless legs, talk to your doctor about potential causes and treatments.