Restless Legs Syndrome affects approximately 10% of adults in the U.S. Researchers believe that RLS is commonly unrecognized or misdiagnosed as insomnia or other neurological, muscular or orthopedic condition.
RLS also affects about 2% of children, according to a study of more than 10,000 families in the U.S. and U.K. The study also found a strong genetic component to RLS; more than 70% of children with RLS had at least one parent with the condition. There is also evidence suggesting that children with attention deficit hyperactivity disorder (ADHD) and a family history of RLS are at risk for more severe ADHD.
RLS may also be confused with depression. According to the Restless Legs Syndrome Foundation, approximately 40% of people with RLS complain of symptoms that would indicate depression if assessed without knowledge or consideration of a sleep disorder.
The exact cause of RLS is unknown.
Primary RLS is the most common type of RLS. It is also referred to as familial (because it is hereditary) or idiopathic (because the causes are unknown) RLS.
Secondary RLS, on the other hand, is believed to be caused by a separate underlying medical condition or in association with the use of certain drugs. For example, some of these conditions include vein disease in the legs such as varicose veins, kidney failure, low levels of iron or anemia, pregnancy, and peripheral neuropathy (a problem with the nerves that carry information to and from the brain and spinal cord that produces pain, loss of sensation, and inability to control muscles). Stress, diet or other environmental factors can also play a role in developing secondary RLS.
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 known 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.
Many studies indicate that RLS symptoms may be caused by underlying varicose veins in the legs. Varicose veins are caused by unhealthy valves within the veins. When these valves fail or leak, the blood falls backward through the poorly functioning valves causing the blood pool and appear enlarged, twisted or bulging. Scientists first theorized a connection with RLS due to the similar side effects of varicose vein sufferers including pain, fatigue, itching, burning, cramping, restlessness and throbbing. In one particular study, clinicians treated 113 RLS patient’s vein disease using non-surgical treatments, and 98% of patients reported relief from the RLS symptoms.
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.
RLS runs in families and may have a genetic component. In a recent study, the first RLS gene was discovered and was shown to account for approximately 50% of RLS cases. However, the researchers who identified the RLS gene cautioned that having it does not guarantee RLS.
Rather, there are likely to be medical, environmental or other factors involved in translating RLS genetic susceptibility into RLS symptoms. Another RLS study also found that a genetic variant may account for about half of RLS cases and revealed an association between RLS and a gene for limb development, suggesting the possibility that RLS has components of a developmental disorder.