Restless legs syndrome is a movement disorder that causes uncomfortable sensations in the legs. These sensations typically are worse during periods of rest, especially just before sleeping at night, but they may happen during daytime periods of inactivity, such as watching a movie, attending a long business meeting, or flying in a plane.
The discomfort of restless legs syndrome usually is accompanied by an overwhelming urge to move the legs, which may relieve leg discomfort temporarily. At night, people with restless legs syndrome often find that their leg symptoms make it difficult to fall asleep. Because of this, insomnia is common, together with extreme drowsiness and fatigue during the daytime.
The cause of restless legs syndrome remains unknown. However, evidence suggests that there is a problem related to a brain chemical (neurotransmitter) called dopamine. Since restless legs syndrome may affect family members across generations, scientists suspect that there is some genetic (inherited) risk of the problem. In addition, genetic studies find an association between certain genes and restless legs syndrome. Still, a definite genetic cause has not been confirmed.
In some people with restless legs syndrome, anemia due to iron deficiency may be a contributing factor, while in others restless legs syndrome has been linked to pregnancy, diabetes, multiple sclerosis, rheumatoid arthritis, kidney failure, varicose veins or peripheral neuropathy (nerve damage in the hands and feet). High caffeine intake (coffee, tea, cola beverages, chocolate) and some vitamin deficiencies also may be related to restless legs syndrome.
Although restless legs syndrome tends to be more common and more severe in people over age 50, it can occur in men and women of any age group, even in young people who may be misdiagnosed as hyperactive. Currently, tens of thousands of people in the United States have restless legs syndrome that is severe enough to disrupt normal daily life. However, researchers estimate that even more people -- possibly up to 3% to 8% of the U.S. population -- may have occasional, milder symptoms of restless legs syndrome.