Epidemiology and Pathophysiology of Restless Legs Syndrome

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Abstract

In 1945 Karl Ekbom coined the term ├óÔé¼´åİrestless legs syndrome™ (RLS), which is still sometimes referred to as Ekbom™s syndrome. RLS is a common sensorimotor condition characterized by predominantly nocturnal dysesthesias relieved by limb movement. RLS is not a new disorder, having been documented in the medical literature for over half a century.1 However, in recent years RLS has been receiving increased attention following approval, in May 2005, by the US Food and Drug Administration (FDA) of the first agent indicated for the treatment of the condition. Also in 2005 the epidemiology and pathophysiology of RLS were reviewed by the RLS Foundation in the RLS Medical Bulletin2 (available at www.rls.org). This article summarizes the current understanding in these fields and highlights the advances made since 2005. The clinical diagnosis and management of RLS are beyond the scope of this article and have been reviewed elsewhere.

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Epidemiology Definition
Epidemiological haracterization necessitates a clear definition of disease. The first normal criteria for the diagnosis of RLS were published by the International RLS Study Group (IRLSSG) in 1995. These criteria were updated in 2002 (see Table 1) and represent the current ‘gold standard’ for diagnosis of RLS.5 The presence of RLS correlates with periodic leg movements of sleep (PLMS) on polysomnography and periodic leg movements of wakefulness (PLMW) on the suggested immobilization test,6 but the diagnosis remains purely clinical. Hence, epidemiological studies rely on subjective reports. The IRLSSG criteria do not specify a cutoff of symptom frequency or severity, although there are many people in whom RLS symptoms are mild and do not impair quality of life (QOL). There has not been a universally accepted definition of clinically significant RLS, although the International RLS Study Group Rating Scale (IRLS) is currently the best validated measure of severity, with a score greater than 10 points (of 40 possible total points) indicating moderate to severe disease.7 Future research will likely employ published validated instruments to define clinically significant RLS.

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Prevalence
Ekbom estimated the prevalence of RLS to be 5% in the general population. Subsequent survey studies have estimated the population prevalence of the disorder to be 1–29%.8 The RLS Epidemiology, Symptoms, and Treatment (REST) trial is the largest survey study to date of RLS prevalence. Questionnaires were completed by 23,052 patients presenting to primary care practices in the US and four Western European countries during a two-week period. Any degree of RLS symptoms was experienced by 11.9% of respondents, 9.6% had at least weekly symptoms, and 551 (2.4% of total respondents, 3.4% of respondents with complete data) had at least twice-weekly symptoms and endorsed a negative impact on QOL.9 Recently, similar figures have been reported in the Irish10 and Spanish11 primary care populations./>/>/>

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