Get Some Sleep: Is restless legs syndrome real?

One question that I am often asked is whether restless legs syndrome is a disorder made up by the pharmaceutical companies.  I can see why people might think that;  few people, including doctors, had heard of  it 20 years ago,  but media reports and ads for medications have put the term into common use.

But as someone who has treated hundreds of patients with this disorder, I can attest to its existence as well as its ability to seriously affect patients’ quality of life.

Restless legs syndrome (RLS) is not the same as foot tapping, nor is it the same as leg cramps.  Patients complain of strange and disturbing feelings usually in their lower legs that usually happen only  in the evening when they are sitting or lying down.  They move their legs voluntarily in an attempt to find relief.  Unfortunately, the minute they stop moving or rubbing their legs, the feeling returns, hence the repeated movement.  In severe cases, the symptoms can begin earlier in the day and can involve the arms or other body parts.  However, when people first develop this problem, it almost always starts in the evening and ends up preventing them from sleeping, which is why it's considered a sleep disorder.

This is a clinical diagnosis, meaning that there is no test that uncovers it.  Rather it is diagnosed based on the constellation of signs and symptoms that patients present.  However, we often do an overnight sleep test because there is a disorder that can go along with RLS which is called Periodic Limb Movement Disorder (PLMD) and this entails rhythmic kicking while asleep.  Sometimes people have PLMD without having RLS, and not all people with RLS will have significant limb movements during their sleep test.

There are population studies that show varying prevalence rates of 5-15%,  but only about 3% of adults and 0.5% of children have it often enough or severe enough to warrant treatment.  There appears to be a genetic component because 40% adults and 70% of children who have primary RLS report that at least one first-degree relative also suffers with this condition.  In most studies, it is approximately twice as common in women as compared to men.  One study found that 27% of pregnant women complained of RLS symptoms.

We do not understand what causes RLS but there seems to be a dysregulation of dopamine, a naturally occurring neurotransmitter.  RLS is greatly increased in patients with Parkinson’s disease, which involves a depletion of dopamine.  It should be noted that people with RLS do not have a depletion of dopamine, just a dysregulation, and there is no evidence that they are at increased risk of developing Parkinson’s disease.

 Iron deficiency can also be involved because in order to synthesize dopamine it is necessary to have sufficient amounts of stored iron in the central nervous system.  Therefore, we do see an increase in prevalence of RLS in people with anemia, end stage kidney disease and in pregnant women, all conditions that involve low levels of the storage form of iron, which is known as ferritin.  There is a simple blood test that can be checked in people with RLS symptoms and if the level is below 50 ng/ml, then oral iron replacement is indicated.  In fact, it is now recommended that all patients with RLS take extra iron each day.

We also know that certain medications can cause or aggravate RLS, medications such as antidepressants, over-the-counter antihistamines and nausea medications such as metoclopramide.  Substances such as caffeine, nicotine and alcohol can also worsen the symptoms of RLS.

If symptoms are very mild or infrequent, then people can try stretching exercises before the time that the symptoms  typically start or they can try doing mentally stimulating tasks such as crossword puzzles, which can help distract them. However, if RLS symptoms occur more than twice a week, most patients want treatment.  Besides adding more iron to the diet, there are several classes of prescription medications that can be used, the most common being dopamine agonists (i.e. synthetic dopamine replacement).  It is important that physicians have experience treating RLS because older dopamine agonists such as carbidopa/levodopa must be used with caution as they can actually worsen the RLS symptoms.

Lisa Shives, M.D., is the founder of Northshore Sleep Medicine in Evanston, Illinois. She’ll blog on Tuesdays on The Chart. Read more from her at Dr. Lisa Shives’ Sleep Better Blog.

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