Restless Legs Syndrome (RLS) is a neurologic sensorimotor disorder that is characterized by an overwhelming urge to move the legs when they are at rest. The urge to move the legs is usually, but not always, accompanied by unpleasant sensations. It is less common but possible to have RLS symptoms in the arms, face, torso, and genital region. RLS symptoms occur during inactivity and they are temporarily relieved by movement or pressure. Symptoms of RLS are most severe in the evening and nighttime hours and can profoundly disrupt a patient's sleep and daily life.

According to the National Center on Sleep Disorders Research, "restless legs syndrome is a common, under diagnosed and treatable condition." Recent research suggests it affects about 10% of adults in North America and Europe with rates increasing with age. Lower prevalence has been found in India, Japan and Singapore, indicating that racial, ethnic or genetic factors are associated with RLS. Researchers believe that RLS is commonly unrecognized or misdiagnosed as insomnia, depression, or other neurological, muscular, or orthopedic condition. A family history of the disorder is present in about 50% of patients.

RLS affects both men and women and can start at any age. It may be confused with growing pains or restlessness when experienced by children. In addition, the severity of the disorder appears to increase with age. Older patients experience symptoms more frequently and for longer periods of time.

The exact cause of RLS is unknown but it has a primary form, not related to other disorders, and a secondary form related to an underlying condition such as kidney failure, pregnancy, or iron deficiency anemia. It may also be caused or made worse by certain medications. This is considered secondary RLS. When no other cause is found for RLS symptoms, it is considered a primary disorder. Primary RLS accounts for 40-60% of RLS diagnoses.

Recently, several research teams have taken a closer look at what might cause primary RLS. In particular, recent studies at Johns Hopkins and Pennsylvania State Colleges have found evidence for brain iron deficiency as a cause for primary RLS. This was first demonstrated in cerebrospinal fluid studies and more recently by the first-ever autopsy analysis of the brains of people with RLS. The autopsy studies reported that cells from the portion of the brain called the substantia nigra showed a deficit in one of the proteins that regulates iron status. However, this evidence suggests that the iron insufficiency in the brain of RLS patients comes directly from a failure of normal iron regulation. In terms of finding a cure, this is good news. The results of this study show that there is no brain damage in people with RLS and that drugs that target the problem of iron uptake may be one way to approach future developments of a treatment.

More than 80 percent of people with RLS also suffer from a condition know as periodic limb movement disorder (PLMD). Characteristics of PLMD include involuntary leg twitching or jerking movements during sleep that occur repeatedly throughout the night and result in disrupted sleep.

In addition to poor quality and short sleep at night, research has shown that people with RLS generally experience a reduced quality of life in the absence of treatment. There is also evidence of a connection between RLS and attention-deficit hyperactivity disorder (ADHD).