Restless legs syndrome (RLS), also known as Willis-Ekbom disease, is a neurological disorder that causes unpleasant or uncomfortable sensations in the legs and an irresistible urge to move them. It is estimated that up to 10% of the U.S. population may have this condition, according to the National Institute of Neurological Disorders and Stroke (NINDS).

Restless legs syndrome is a disorder of both sleep and movement. Symptoms commonly occur in the evening hours and are often most intense at night, making it difficult to fall asleep or return to sleep after waking up, according to the Mayo Clinic. Moving the legs or walking typically relieves the discomfort.

RLS can begin at any age, but the symptoms typically become more frequent and last longer with age, according to the NINDS. The disorder also affects twice as many women as men.

Restless legs syndrome: symptoms

The primary symptom of restless legs syndrome is an intense urge to move the legs, accompanied by uncomfortable sensations in the lower limbs, such as aching, throbbing, pulling, itching, crawling or creeping. These sensations less commonly affect the arms, chest or head, and are relieved or minimized with movement, according to the NINDS.

Symptoms typically occur after sitting for extended periods of time, for example when taking a trip by plane or watching a movie. Their severity and frequency may vary from day to day, and from person to person.

According to the Sleep Foundation, a U.S. nonprofit organization, restless legs syndrome is often accompanied by insomnia, with 88% of individuals with this disorder reporting at least one sleep-related symptom. Many people who have RLS can also have a disorder called periodic limb movements in sleep (PLMS). Signs of this disorder are quick movements of the legs every 20 to 40 seconds during the night.

Scientists have also found a significant link between RLS and irritable Bowel Syndrome, according to a 2021 review published in the journal Sleep Medicine. However, more studies are needed to fully understand this association.

Restless legs syndrome: Causes

The cause of restless legs syndrome is largely unknown, according to the Johns Hopkins Center for Restless Legs Syndrome. Some individuals may be genetically predisposed for the condition, while other cases may be linked to disrupted brain functioning or faulty iron metabolism. Symptoms may also be caused by certain medications or nerve damage in the legs due to diabetes, kidney problems or alcoholism.

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Some evidence suggests that restless legs syndrome may be caused by low levels of dopamine, a neurotransmitter necessary for smooth muscle activity and movement. Dopamine levels tend to fall towards the end of the day, which may explain why the symptoms of restless legs syndrome are often worse in the evening and during the night.

The brains of individuals with RLS do not store sufficient levels of iron in dopamine-producing cells, which in turn may slow down the release of this neurotransmitter, according to a 2022 review published in the journal Experimental Neurology.

Restless legs syndrome may also be caused by a dysfunction in the brain's basal ganglia circuits, according to a 2021 brain imaging study published in the journal Sleep Medicine.

Basal ganglia are structures in the brain that are responsible for involuntary movements. This dysfunction disrupts the production of dopamine and may cause the jerky motions characteristic of RLS.

The most common type of restless legs syndrome, called primary RLS, often runs in families, according to the Sleep Foundation. A 2018 review of twin studies published in the journal Sleep Medicine Reviews identified several gene variants that may increase the risk of developing this disorder. Researchers cautioned, however, that having the genetic predisposition does not guarantee that a person will have RLS.

Female reproductive hormones may also play a role in the development of restless legs syndrome, which could explain why women are more likely to have this disorder, according to a 2020 review published in the International Journal of Environmental Research and Public Health.

Secondary RLS is thought to be a condition of another disease or a side effect of certain drugs, according to the NINDS.

Restless legs syndrome: Diagnosis

The diagnosis of restless legs syndrome is quite simple. According to the NINDS, a doctor will listen to the patient's symptoms and see if they match the five criteria of RLS:

The patient has strong and irresistible urges to move their legs and uncomfortable sensations that often accompany the urgesThe symptoms start or get worse while the patient is lying down or restingThe symptoms get better or are relieved somewhat when the patient movesThe symptoms are worse at nightThe above four features are not due to any other medical or behavioral problem A doctor may want to conduct blood tests and neurological exams to try to determine what factors are causing the symptoms. Patients may also be referred to a sleep specialist for an overnight examination.

Restless legs syndrome: Treatment

The treatment of RLS is usually focused on relieving symptoms, according to the NINDS. Moving the affected limbs may provide temporary relief. Sometimes, RLS symptoms can be controlled by finding and treating an associated medical condition, such as peripheral neuropathy or diabetes.

"You should approach treatment by addressing the two areas linked to RLS: the brain and the muscles," said Dr. Michael A. Smith, a senior health scientist for the Life Extension Foundation in Florida.