Prevalence, severity and risk factors of restless legs syndrome in the general adult population in two Scandinavian countries

Diurnal cycle influences peripheral and brain iron levels in mice

Iron movement between organ pools involves a dynamic equilibrium of iron efflux and uptake, and homeostatic mechanisms are likely involved in providing iron to cells and organs when required. Daily iron levels in the plasma pool fluctuate with the diurnal cycle, but clear explanations regarding the objectives and regulation of the flux are lacking. The association between diurnal cycle and iron flux is relevant in the disease of restless legs syndrome (RLS), where individuals display diurnal deficits in motor control, have impaired brain iron metabolism, and perhaps altered iron uptake from the plasma pool. The goal of the present study was to examine diurnal variations in peripheral and regional brain iron to evaluate iron flux between organs in iron-sufficient and iron-deficient mice. In mice fed control diet, liver iron was elevated 30-40%, and plasma iron was reduced 20-30% in the active dark period compared with the inactive light phase. Dietary iron deficiency eliminated this variation in liver iron in male and female mice and in plasma iron in male mice. Reductions in ventral midbrain and nucleus accumbens iron and ferritin were apparent in iron-deficient mice during both diurnal phases, but only during the light phase was an approximately 25% reduction in whole brain iron observed, suggesting different brain iron requirements between phases. These data demonstrate that iron flux between organs is sensitive to diurnal regulatory biology. Importantly, variations in brain iron may have temporal implications regarding neural functioning and may contribute to the diurnal cycle-dependent symptoms of RLS.

Restless legs syndrome and its relationship with insomnia symptoms and daytime distress: epidemiological survey in Sweden

To investigate prevalence estimates of restless legs syndrome (RLS) in relation to insomnia complaints and daytime distress a questionnaire was sent to a randomly selected sample of 1962 inhabitants of Uppsala, Sweden. The questionnaire included questions about sleep and daytime distress and the standardized four-question set for epidemiological settings recommended by the International RLS Study Group. A positive diagnosis of RLS was established in 18.8% of all responders. When the optional question about frequency was applied 5.8% reported frequent symptoms. Insomnia symptoms and daytime distress were significantly associated with the frequency of RLS symptoms.

Restless legs symptoms with sleepiness in relation to mortality: 20-year follow-up study of a middle-aged Swedish population

AIM

The aim of the present study was to investigate restless legs symptoms with concomitant daytime sleepiness as a risk factor for mortality in a middle-aged population.

METHODS

A cohort of 5102 subjects aged 30-65 years in mid-Sweden who responded to a postal questionnaire in 1983 was followed up. The questionnaire included questions about restless legs symptoms, daytime sleepiness, demographic and lifestyle variables, sleep habits, medical conditions and depression. Mortality data for the period 1983-2003 were collected and death certificates were available for all the 657 responders who died during the follow-up period.

RESULTS

Restless legs symptoms with daytime sleepiness was reported by 10.3% and was associated with shorter night sleep time, several health problems and depression. During the follow-up period 379 men (21.6%) and 278 women (15.5%) died. A multivariate model adjusted for age, short night sleep time, lifestyle factors, medical conditions and depression showed that women reporting restless legs symptoms with daytime sleepiness had an excess mortality compared to women without restless legs symptoms and daytime sleepiness (hazard ratios, 1.85; 95% confidence interval, 1.20-2.85; P = 0.005). No influence on mortality risk was found in men reporting restless legs symptoms with daytime sleepiness.

CONCLUSIONS

The occurrence of restless legs symptoms with daytime sleepiness in middle-aged women is associated with increased mortality risk.

Restless legs syndrome and periodic limb movement disorder in children and adolescents

Restless Legs Syndrome (RLS) has been recognized as a common and treatable neurologic disorder in adults for some time, but the occurrence of RLS in children and adolescents has seen relatively delayed acceptance. A large, population-based study has recently reported a 1.9% and 2% prevalence of RLS in children and adolescents, respectively. RLS in children is closely associated with periodic limb movement disorder (PLMD), and symptoms of both may range from mild to severe. An early, accurate diagnosis of RLS or PLMD provides substantial benefits to an individual's quality of life, especially in cases of poor-sleep related intellectual or emotional dysfunction. Treatment plans should use emerging knowledge of how RLS and PLMD affect children and adolescents to correctly identify these disorders and aim to reduce or eliminate symptoms. Best-fitting therapy will consider severity of symptoms, comorbid conditions, and phenotypic variables. Promising progress has been made in understanding the genetic components of RLS as well as the role of iron deficiency in exacerbating symptoms. A review of current research on RLS and PLMD in children and adolescents is presented.

Epidemiology of restless legs syndrome in Korean adults

STUDY OBJECTIVES

To investigate the prevalence of restless legs syndrome (RLS) in Korea.

DESIGN

A large population-based telephone interview method using the Korean version of the Johns Hopkins telephone diagnostic interview for the RLS.

SETTING

A computer aided telephone interview method.

PARTICIPANTS

A total of 5,000 subjects (2,470 men and 2,530 women) were interviewed in depth. A representative sample aged 20 to 69 years was constituted according to a stratified, multistage random sampling method.

INTERVENTIONS

N/A.

MEASUREMENTS AND RESULTS

Of the respondents, 373 respondents (7.5%) of the population (pop) met the criteria for the definite or probable RLS groups: 194 (3.9% of pop) respondents fulfilled the criteria for definite RLS and 179 (3.6% of pop) respondents fulfilled the criteria for probable RLS. The prevalence of RLS was generally higher for women than men (4.4% vs. 3.3% for definite, 8.7% vs. 6.2% for definite plus probable). About 90% of RLS individuals were experiencing symptoms at the time of the interview and this was similar for both RLS groups. Seventy-four respondents (1.48%) reported symptoms were moderately or severely distressing and were therefore classified as RLS "sufferers." Of those with a diagnosis of RLS sufferer, 24.3% reported being treated for their symptoms, compared to 12.4% of RLS not designated a "sufferer."

CONCLUSION

RLS is common and underdiagnosed in Korea with nearly 1% of the population reporting disturbed sleep related to their RLS. These results are comparable to other countries.

Restless legs syndrome in Parkinson's disease

The present study explores the frequency of RLS in PD and focuses on the clinical differences between patients with and without restless legs syndrome (RLS). A cross-sectional study was designed, comprising 114 patients diagnosed with PD. Those patients positive for RLS were assessed for intensity of the syndrome (IRLS). We compared the clinical characteristics of the patients with and without RLS, using specific scales: Unified Parkinson's Disease Rating Scale (UPDRS I-IV), quality of life (Parkinson's Disease Questionnaire, PDQ 39), sleep symptoms (Parkinson's Disease Sleep Scale, PDSS), and diurnal hypersomnia (Epworth Sleepiness Scale). Twenty-five patients (21.9%) out of a total of 114 subjects diagnosed with PD met the RLS diagnostic criteria. RLS was more frequent in women (68%). The patients with RLS showed poorer scores on the PDSS (PD-RLS+: 102.4 +/- 15.1 vs PD-RLS-: 113.2 +/- 16.4) (P = 0.005) and in the bodily discomfort dimension of the PDQ-39 (PD-RLS+ 6.1 +/- 3.4 vs PD-RLS- 3.8 +/- 2.6) (P = 0.002). Analysis of the subscales of the PDSS showed significant differences (P < 0.001) between both groups of patients in items 4 and 10, and to a lesser degree in items 5 (P = 0.01) and 11 (P = 0.02) There was no increased incidence of diurnal hypersomnia in the group of patients with RLS. There were no differences in the rest of the variables. RLS is frequent in patients with PD, though this condition doesn't apparently affect quality of life or lead to an increased presence of diurnal hypersomnia. It would be advisable to validate the diagnostic criteria of RLS in this specific group of patients.

Genetic association studies of neurotensin gene and restless legs syndrome in French Canadians

BACKGROUND AND PURPOSE

The neurotensin gene (NTS), a known dopamine modulator, is located within the candidate region for the first genetic locus of restless legs syndrome (RLS1) on chromosome 12q. Though no causative mutation was found in selected patients in a previous mutation analysis, the involvement of NTS in RLS cannot be completely excluded as a potential positional and functional candidate gene. The purpose of the current study is to further explore the NTS gene for potential functional variant(s) in its entire genomic and potential regulatory regions and their possible association with RLS symptoms.

METHODS AND SUBJECTS

We resequenced the coding regions and sequenced all the intronic and potential regulatory regions of the NTS gene in additional patients and controls. We carried out full scale gene-based case-control and family-based genetic association studies using the sequence variants detected during mutational analysis.

RESULTS

No coding or variants in regulatory and intronic regions compatible with a deleterious mutation were detected. Seven polymorphisms with elevated allele frequencies in the Caucasian population did not show association with RLS in two independent case-control groups and 110 RLS families.

CONCLUSION

The NTS gene on chromosome 12q is most unlikely to play a direct role in RLS etiology.

Genetics of restless legs syndrome (RLS): State-of-the-art and future directions

Several studies demonstrated that 60% of restless legs syndrome (RLS) patients have a positive family history and it has been suggested that RLS is a highly hereditary trait. To date, several loci have been mapped but no gene has been identified yet. Phenocopies and possible nonpenetrants made it difficult to detect a common segregating haplotype within the families. Defining the exact candidate region is hampered by possible intrafamilial, allelic, and nonallelic heterogeneity. One important prerequisite for future successful genetic studies in RLS is the availability of large and thoroughly phenotyped patients and family samples for linkage as well as association studies.

Restless legs syndrome in older adults

Restless legs syndrome (RLS) is a common neurological disorder characterized by an urge to move the legs. The symptoms show a strong circadian rhythmicity, with onset or increase in the evening or at night; thus, sleep disturbances are the most frequent reason for patients seeking medical aid. The prevalence of the disorder increases strongly with age, with an estimated 9% to 20% of sufferers being among the elderly. Dopaminergic drugs are the first-line treatment option in RLS; opioids and anticonvulsants can also be used either as add-on or stand alone therapy options. Secondary forms of RLS and possible interaction with other medications require particular consideration in the elderly.

Restless Legs Syndrome

Restless legs syndrome is a symptomatic urge to move the legs, usually accompanied or caused by uncomfortable/ unpleasant sensations deep within the legs that begin or are worsened during periods of rest or inactivity in the evening or night and are partially or totally relieved by movement. It can occur intermittently or daily. Nonpharmacologic treatments include moderate exercise; good sleep hygiene; elimination of alcohol, caffeine, and nicotine; and hot baths, massage, and stretching. Activities promoting mental alertness may improve symptoms. Moderate exercise and use of nasal continuous positive airway pressure are the only nonpharmacologic treatments with proven benefit. For intermittent restless legs syndrome, carbidopa/levodopa and nonpharmacologic therapy are recommended as primary treatments. For daily restless legs syndrome, dopamine agonists, particularly ropinirole and pramipexole, are suggested as the drugs of choice. Carbidopa/levodopa could be considered for daily restless legs syndrome, but augmentation is a significant drawback to its use. Carbamazepine and gabapentin have limited data to support their use.

Comorbidity in restless legs syndrome among a sample of Swedish adults

BACKGROUND

Restless legs syndrome (RLS) is a neurological movement disorder, which often causes sleep problems. However, the comorbidity of this disorder is not well known. This study aimed to document the prevalence of RLS in the general population of Sweden and to identify factors associated with this condition.

METHODS

A cross-sectional study was performed in Sweden. One thousand subjects aged 18-90 years old underwent telephone interviews. The questionnaire assessed such factors as sleep variables, depressive mood, treatment of diabetes mellitus, and treatment with drugs for depression during the previous four-week period. RLS was diagnosed based on the minimal criteria provided by the International RLS Study Group.

RESULTS

The prevalence of RLS was 5% (5.7% in women, 3.5% in men). Severe or very severe RLS symptoms during the previous week were noted by 64% of the RLS subjects. Factors associated with RLS were insomnia, excessive daytime sleepiness, periodic limb movements in sleep, and depressed mood. Those affected by RLS were not more often consumers of drugs for depression than non-RLS subjects.

CONCLUSIONS

RLS is prevalent in the general population in Sweden. RLS negatively influenced sleep and was associated with depressed mood. Antidepressive drug treatment was not associated with RLS.

Childhood and adult factors associated with restless legs syndrome (RLS) diagnosis

BACKGROUND AND PURPOSE

RLS appears to be caused by a complex interaction of genetic and environmental factors. This study sought to identify some environmental risk factors significantly associated with the occurrence of RLS.

PATIENTS AND METHODS

Three adult behaviors and 10 childhood factors potentially related to development of RLS were evaluated for significant association with the occurrence of RLS in a large case-controlled family history study. All available family members of the probands in this study were evaluated for RLS using a validated diagnostic telephone interview that included a background questionnaire covering factors potentially associated with the development of RLS. Where possible, the mothers of the subjects were also interviewed regarding developmental factors that might affect the child's health and perhaps occurrence of RLS. All family members with a definite diagnosis of RLS or Not-RLS were included in the study. Of a total of 973 participants, 262 (27%) had RLS and 711 did not.

RESULTS

An odds ratio (OR) with 95% confidence limits (CI) was calculated for the relationship of each factor to RLS diagnosis. Restless sleep in childhood was associated with an increased risk of developing RLS later in life for both men (OR=2.64; 95% CI: 1.31-5.29) and women (OR=2.54; 95% CI: 1.41-4.59). Blood donation was also significantly associated with an increased risk of developing RLS among men only (OR=1.99; 95% CI: 1.10-3.58), which was more pronounced for those donating blood more than the median number of donations for this group of five (OR=2.3, 95% CI: 1.16-4.43). No other factor was significantly associated with the occurrence of RLS.

CONCLUSIONS

This is the first case-controlled study that demonstrates a significant association between blood donation and the occurrence of RLS in males. The association was most significant for those men donating five or more times. Smoking and alcohol use were not related to the occurrence of RLS. Neither childhood growing pains nor attention-deficit hyperactivity disorder (ADHD) was related to RLS. The only consistent factor found related to prevalence of RLS for both men and women was the report of 'restless sleep' in childhood.

Perceived severity of restless legs syndrome across the female life cycle

BACKGROUND

As with migraine, female sex hormones may explain the high prevalence of restless legs syndrome (RLS) in women and therefore influence RLS severity across the female life cycle.

OBJECTIVE AND METHODS

To test this hypothesis, we performed a questionnaire-based transversal survey in female members of the French Association of patients with RLS. Five hundred thirty-six women fulfilled the RLS criteria and completed the International RLS Severity Scale (IRLSSS) and questionnaire about reproductive behaviour, RLS history and perception of RLS symptom severity during pregnancy, menses and menopause.

RESULTS

Patients with at least one child showed a significantly higher mean IRLSSS score than women without children and 23% of the patients declared having perceived worsening of symptoms during pregnancy. Perceived RLS severity was increased during menses in 29% of non-menopaused patients and 69% of the patients reported worsening of symptoms following menopause. In these patients, a tendency towards higher IRLSSS scores was noted. Regression analysis revealed a correlation between higher IRLSSS scores and an early age at onset of RLS.

CONCLUSIONS

Female hormonal changes do not account for the variation in perceived severity in women with RLS during their hormonal milestones and their role in the pathophysiology of RLS is unlikely.

Restless legs syndrome: prevalence and impact in children and adolescents--the Peds REST study

OBJECTIVES

Restless legs syndrome, a common neurologic sleep disorder, occurs in 5% to 10% of adults in the United States and Western Europe. Although approximately 25% of adults with restless legs syndrome report onset of symptoms between the ages of 10 and 20 years, there is very little literature looking directly at the prevalence in children and adolescents. In this first population-based study to use specific pediatric diagnostic criteria, we examined the prevalence and impact of restless legs syndrome in 2 age groups: 8 to 11 and 12 to 17 years.

METHODS

Initially blinded to survey topic, families were recruited from a large, volunteer research panel in the United Kingdom and United States. Administration was via the Internet, and results were stratified by age and gender. National Institutes of Health pediatric restless legs syndrome diagnostic criteria (2003) were used, and questions were specifically constructed to exclude positional discomfort, leg cramps, arthralgias, and sore muscles being counted as restless legs syndrome.

RESULTS

Data were collected from 10,523 families. Criteria for definite restless legs syndrome were met by 1.9% of 8- to 11-year-olds and 2.0% of 12- to 17-year-olds. Moderately or severely distressing restless legs syndrome symptoms were reported to occur > or = 2 times per week in 0.5% and 1.0% of children, respectively. Convincing descriptions of restless legs syndrome symptoms were provided. No significant gender differences were found. At least 1 biological parent reported having restless legs syndrome symptoms in > 70% of the families, with both parents affected in 16% of the families. Sleep disturbance was significantly more common in children and adolescents with restless legs syndrome than in controls (69.4% vs 39.6%), as was a history of "growing pains" (80.6% vs 63.2%). Various consequences were attributed to restless legs syndrome, including 49.5% endorsing a "negative effect on mood." Data were also collected on comorbid conditions and restless legs diagnosis rates.

CONCLUSIONS

These population-based data suggest that restless legs syndrome is prevalent and troublesome in children and adolescents, occurring more commonly than epilepsy or diabetes.

Characteristics and clinical correlates of restless legs syndrome in schizophrenia

OBJECTIVE

The cause of restless legs syndrome (RLS) has not yet been ascertained, but one of the most promising theories involves dopaminergic deficiency. In accordance with this theory, we assumed that the prevalence of RLS would be higher among schizophrenics treated with antipsychotics than in the normal population. The purpose of this study was to establish the prevalence, characteristics, and clinical correlates of RLS in schizophrenic patients undergoing treatment with antipsychotics.

METHODS

A total of 182 hospitalized schizophrenic patients and 108 age- and sex-matched normal controls were enrolled. The presence of RLS and its severity were assessed using the International Restless Legs Syndrome Study Group (IRLSSG) diagnostic criteria and the IRLSSG rating scale, respectively. The Athens Insomnia Scale (AIS), Brief Psychiatric Rating Scale (BPRS), and Barnes Akathisia Rating Scale (BARS) were used to evaluate insomnia, global psychiatric symptoms, and akathisia, respectively, in schizophrenic patients.

RESULTS

Of the 182 schizophrenic patients, 39 (21.4%) were found to have RLS and 87 (47.8%) met at least one of the RLS diagnostic criteria. The prevalence of RLS was significantly higher in the schizophrenia group than in the control group (p=0.009), as were the RLS scores (p<0.001). The BPRS (p=0.001) and the AIS (p<0.001) scores were higher in the RLS group than in the group with no RLS symptoms.

CONCLUSION

We conclude that it is important to consider the diagnosis of RLS when schizophrenic patients complain of insomnia, and that RLS symptoms could be associated with more severe psychiatric symptoms and insomnia.

Skeletal Muscle Morphology in Patients with Restless Legs Syndrome

AIM

The aim of the study was to assess the cellular and structural properties of skeletal muscle in restless legs syndrome (RLS).

METHOD

Twenty patients and 16 controls were included. Aerobic performance was assessed using a submaximal test. On muscle biopsies taken from the tibialis anterior, fiber distribution and fiber area were analyzed together with parameters surveying the microvascularization, especially the tortuosity, which is expressed as a percent of muscle fiber perimeter in contact with the wall of the microvessel, length of capillary/perimeter of fiber (LC/PF) index.

RESULTS

The RLS group had significantly lower predicted maximal oxygen uptake (p = 0.01) and significantly higher LC/PF index (p = 0.01) compared to the controls.

CONCLUSION

The higher capillary tortuosity in RLS patients indicates the occurrence of significant remodeling in capillary geometry in RLS.

Prevalence of restless legs syndrome and REM sleep behavior disorder in multiple sclerosis

A total of 135 consecutive, unrelated, multiple sclerosis (MS) patients were interviewed for symptoms suggestive of restless legs syndrome (RLS) and REM sleep behavior disorder (RBD), using semi-structured questionnaires. Some 118 unrelated healthy controls of similar sex and age distribution were included for comparison. Patients and controls with equivocal symptoms were re-evaluated by a sleep disorders specialist and video-polisomnography in those who fulfilled the criteria for RBD. We did not find significant differences in frequency (13.3 versus 9.3%), proportion of females (66.7 versus 58.5%), and mean age (42.1±12.6 versus 43±7.8 years) among MS patients and controls with RLS. RBD was found in three patients (1.4%), one associated with antidepressant intake, but in none of the controls. Our study shows that RLS in MS is not more frequent than in the general population, and that RBD, although uncommon, may occur in the setting of this neurological disease. Multiple Sclerosis 2007; 13: 805-808. http://msj.sagepub.com

Effects of restless legs syndrome (RLS) on sleep

Restless legs syndrome (RLS) is a common neurological disorder characterized by an irresistible urge to move the legs, usually accompanied or caused by uncomfortable sensations in the legs. Symptoms are worse in the evening or at night than during the day and generally begin or worsen during periods of rest or inactivity. The chronic sleep disturbance often associated with RLS is likely due, at least in part, to the circadian nature of the symptoms. The relationship between disturbed sleep and reduced daytime functioning is well known and thus the accurate diagnosis and effective management of RLS is imperative.

Restless Legs Syndrome

Restless legs syndrome (RLS) is a common and often disabling sensorimotor disorder. Epidemiologic studies suggest that RLS is an underrecognized and undertreated disorder affecting both children and adults. The diagnosis is based primarily on the following four essential criteria: (1) an urge to move, usually associated with paresthesias, (2) onset or exacerbation of symptoms at rest, (3) relief of symptoms with movement, and (4) symptoms manifesting in a circadian pattern. Supplemental workup including polysomnography, iron profile, and/or neuropathy screen can provide support for the diagnosis and aid in the treatment strategy. Behavioral techniques, dopaminergic agents, opiates, benzodiazepines, and antiepileptics all have potential value in treating this disorder. Dopaminergic agents continue to be the most effective RLS treatment. However, due to their potential long-term side effects, these agents should not be considered the sole treatment of choice. In the end, the therapeutic plan should be individualized to suit each patient's presentation and needs.

Prevalence of restless legs syndrome among native South Americans residing in coastal and mountainous areas

OBJECTIVE

To determine the prevalence of restless legs syndrome (RLS) in native South Americans and identify the impact of geographic location.

PARTICIPANTS AND METHODS

An epidemiological telephone survey of RLS symptoms involving natives from coastal and mountainous areas was performed during July 2, 2004, through September 28, 2004. The process consisted of 2 phases: the creation of the epidemiological instrument and the telephone survey.

RESULTS

Five hundred adults, 250 from the mountainous regions and 250 from the coastal region (190 men and 310 women; age range, 25-85 years) were interviewed and subsequently divided on the basis of International Restless Legs Syndrome Study Group criteria into those who had RLS (RLS+ group) and those who did not (RLS- group). Ten (2.0%) had RLS. The overall rate of RLS in adults living in the mountainous region at 2816 m above sea level (3.2% [8/250]) was significantly higher than that for adults living in the coastal region at 4 m above sea level (0.80% [2/250]; P = .002). The mean age of the RLS+ group was 49.5 years (SD, 15.20 years; range, 25-85 years).

CONCLUSION

Native South American adults have a prevalence of RLS well below that reported in populations with European ancestry but similar to that in Asian and Turkish populations. Furthermore, in Ecuador, geographic differences were identified in areas of similar population density.

Genetics of restless legs syndrome

Several studies on restless legs syndrome (RLS) have suggested a substantial genetic contribution in the etiology of this sleep disorder. Clinical surveys of idiopathic RLS patients have shown that 40-90% report a positive family history. The clinical features have been compared between familial and sporadic cases and the only difference found was a younger age-at-onset in familial RLS. Despite several reports suggesting a genetic contribution to the etiology of idiopathic RLS, few molecular genetic studies have been carried out attempting to identify genes that can predispose to this disorder. In particular, genes encoding for the GABA A receptor subunits, the gene for the alpha1 subunit of the glycine receptor, and genes involved in dopaminergic transmission and metabolism have been analyzed, however no significant findings have been reported. Genomewide linkage analysis studies using microsatellite markers have identified three loci for RLS: on chromosome 12q, on chromosome 14q and on chromosome 9p. It is important to investigate whether further RLS families show linkage to one of these loci to discuss the contribution of these loci and to provide a prerequisite of a mutational screening and identification of the RLS genes.

Genetics of restless legs syndrome

Restless legs syndrome (RLS) is a common disorder, although under-diagnosed, with a prevalence of up to 15% depending on the population sampled. Familial aggregation has been widely shown since Ekbom formerly described the condition in 1960; twin studies support a genetic contribution in the development of this disorder. Molecular genetic approaches have identified three genomic regions in RLS susceptibility, however no specific mutations have yet been identified. Herein, we review the current status of genetics in RLS, providing some methodological guidelines to help future research.

The restless legs syndrome

The restless legs syndrome (RLS) is one of the commonest neurological sensorimotor disorders at least in the Western countries and is often associated with periodic limb movements (PLM) during sleep leading to severe insomnia. However, it remains largely underdiagnosed and its underlying pathogenesis is presently unknown. Women are more affected than men and early-onset disease is associated with familial cases. A genetic origin has been suggested but the mode of inheritance is unknown. Secondary causes of RLS may share a common underlying pathophysiology implicating iron deficiency or misuse. The excellent response to dopaminegic drugs points to a central role of dopamine in the pathophysiology of RLS. Iron may also represent a primary factor in the development of RLS, as suggested by recent pathological and brain imaging studies. However, the way dopamine and iron, and probably other compounds, interact to generate the circadian pattern in the occurrence of RLS and PLM symptoms remains unknown. The same is also the case for the level of interaction of the two compounds within the central nervous system (CNS). Recent electrophysiological and animals studies suggest that complex spinal mechanisms are involved in the generation of RLS and PLM symptomatology. Dopamine modulation of spinal reflexes through dopamine D3 receptors was recently highlighted in animal models. The present review suggests that RLS is a complex disorder that may result from a complex dysfunction of interacting neuronal networks at one or several levels of the CNS and involving numerous neurotransmitter systems.