Restless legs syndrome, or RLS, is a neurological sleep-related movement disorder characterised by an urge to move the legs, usually accompanied by unpleasant sensations. The sensations are often described as crawling, creeping, pulling, tingling, aching, throbbing or an internal feeling of restlessness, although descriptions vary. A defining feature is that symptoms typically occur or worsen during periods of rest or inactivity, are relieved at least temporarily by movement and are particularly prominent in the evening or at night. The condition can interfere substantially with falling asleep and maintaining sleep.
RLS is distinguished from ordinary muscle discomfort because of its characteristic pattern. Symptoms are linked to rest, tend to improve with movement and commonly follow a circadian pattern with greater severity during the evening or night. People may repeatedly get out of bed, walk around, stretch their legs or move them under the covers to obtain relief. The sensations are often difficult to describe because they do not necessarily correspond to conventional pain. The urge to move is a central feature rather than simply a response to a painful muscle or joint.
RLS can be primary, meaning no single underlying cause is identified, or secondary to another condition or physiological factor. Iron deficiency is an important association because iron participates in dopamine-related pathways in the brain, and low brain iron availability is thought to contribute to RLS in susceptible individuals. RLS can also occur in association with pregnancy, particularly later pregnancy, and with certain medical conditions. Kidney disease is another recognised association. The precise causal pathway varies between individuals and is still an active area of research.
Genetics can play a significant role, particularly in earlier-onset RLS. Several genetic variants have been associated with susceptibility, although genes do not determine the condition in every person. Family history is common in some forms. The underlying biology involves brain networks regulating movement and sensory processing, with dopaminergic mechanisms and brain iron metabolism implicated. RLS is not simply a problem of poor circulation, although sensations can be perceived in the legs and may be confused with vascular discomfort or other conditions.
RLS can produce substantial sleep disruption. Difficulty remaining still can delay sleep onset, and repeated symptoms can cause fragmented sleep. Chronic sleep disruption can subsequently contribute to daytime fatigue, reduced concentration, irritability and impaired quality of life. In severe cases, people may avoid situations requiring prolonged sitting, such as long journeys, cinema visits or meetings, because symptoms become difficult to tolerate. The condition therefore affects both nocturnal sleep and waking activities.
Several substances and medicines can worsen RLS in susceptible people. Some antihistamines, antidepressants and other drugs have been associated with exacerbation, although medication effects vary and treatment decisions should be individualised. Caffeine and alcohol can affect symptoms or sleep in some people, but responses differ. Iron deficiency should be considered where clinically appropriate, and laboratory assessment of iron status may be useful when RLS is suspected. Iron supplementation should not be undertaken indiscriminately because excess iron can be harmful and the appropriate treatment depends on laboratory findings and clinical context.
Diagnosis is primarily clinical because there is no single definitive blood test or imaging scan for RLS. Clinicians consider the characteristic symptom pattern and exclude mimics. Conditions such as nocturnal leg cramps, peripheral neuropathy, arthritis, positional discomfort and akathisia can produce leg sensations or an urge to move but have different defining features. A careful history therefore matters. The timing of symptoms, relationship to rest, response to movement and evening predominance are particularly informative.
Management depends on severity and cause. Correcting confirmed iron deficiency or another underlying contributor can be important. Behavioural measures may include maintaining regular sleep, moderate physical activity and avoiding individual triggers. For persistent clinically significant symptoms, healthcare professionals may consider medicines, but treatment choices require attention to adverse effects and long-term risks. Dopamine-related medicines can provide short-term benefit but may cause augmentation, in which symptoms become earlier, more intense or spread to other body regions, so modern management often considers other treatment options where appropriate.
