title: Age-at-onset in restless legs syndrome: a clinical and polysomnographic study.
abstract: OBJECTIVE
  To determine the distribution of age-at-onset in a large cohort of patients with restless legs syndrome (RLS) and to compare clinical and polysomnographic characteristics of patients with early and late age-at-onset of RLS.
  
  
  METHODS
  Two hundred and fifty patients with RLS were studied. Information on age-at-onset, etiology, familial history and symptoms severity of RLS was obtained. Age-at-onset density functions were determined from bootstrap methods and kernel density estimators.
  
  
  RESULTS
  Age-at-onset showed a significant bimodal distribution with a large peak occurring at 20 years of age and a smaller peak in the mid-40s. Early- and late-onset RLS could be separated with a cut-off at 36 years of age. Distributions of age-at-onset differed as a function of presence/absence of a familial history and etiology of RLS. Age-at-onset clearly differentiated patients with a primary RLS (early onset) from those with secondary RLS. Finally, early-onset RLS was associated with increased RLS severity with higher indices of periodic leg movements in sleep (PLMS) associated with microarousals and periodic leg movements during wakefulness (PLMW).
  
  
  CONCLUSIONS
  Early- and late-onset RLS could be distinguished depending on familial history and etiology of RLS. Our data suggest that different pathological processes are involved in these two groups, the early-onset group being highly genetically determined.
authors.affiliation: Sleep Disorders Center, Centre d'étude du sommeil et des rythmes biologiques, Hôpital du Sacré-Coeur de Montréal, 5400 boul. Gouin Ouest, Montréal, Que., Canada H4J 1C5.
authors.forename: S
authors.initials: S
authors.lastname: Whittom
authors.forename: Y
authors.initials: Y
authors.lastname: Dauvilliers
authors.forename: M-H
authors.initials: MH
authors.lastname: Pennestri
authors.forename: F
authors.initials: F
authors.lastname: Vercauteren
authors.forename: N
authors.initials: N
authors.lastname: Molinari
authors.forename: D
authors.initials: D
authors.lastname: Petit
authors.forename: J
authors.initials: J
authors.lastname: Montplaisir
mesh_terms: D000328:Adult; D017677:Age Distribution; D017668:Age of Onset; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D020189:Nocturnal Myoclonus Syndrome / Q000175:diagnosis* / Q000453:epidemiology; D017286:Polysomnography / Q000379:methods; D012148:Restless Legs Syndrome / Q000175:diagnosis* / Q000453:epidemiology; D012720:Severity of Illness Index