title: Correlates of PLMs variability over multiple nights and impact upon RLS diagnosis.
abstract: OBJECTIVE
  Night-to-night variability of periodic leg movements (PLMs) in restless legs syndrome (RLS) was examined to define the range of intra-subject values, impact upon diagnosing RLS, and clinical correlates.
  
  
  METHODS
  Twenty RLS patients were monitored for 10-15 nights using a validated, tri-axial accelerometer worn on the ankle.
  
  
  RESULTS
  The mean difference in PLMs index (PLMI) between the lowest and highest night was 25.1/h (range: 3.9-73.8). Inter-subject differences accounted for nearly five times the variance in PLMI relative to between nights within an individual. Based on a single night of recording, PLMI criterion thresholds of 5, 10, and 15/h were exceeded on approximately 70.1%, 51.9% and 34.1% of individual nights among these patients. Based on five randomly sampled nights of recordings, the likelihood that such thresholds were met on at least a single night increased to 91.2%, 80.8% and 62.7%, respectively. Women exhibited greater variability.
  
  
  CONCLUSIONS
  Variability in PLMs within RLS subjects was substantial, yet individuals' characteristic PLM level represented a quantitative trait. Variability was unrelated to age or scores on scales of RLS severity, sleepiness, functional status, and mood. A larger number of recording nights increased the likelihood that any criterion was reached.
authors.affiliation: Department of Neurology and Program in Sleep, Emory University, 101 Woodruff Circle-WMRB, Suite 6000, Atlanta, GA 30322, USA. lbecke2@emory.edu
authors.forename: Lynn Marie
authors.initials: LM
authors.lastname: Trotti
authors.forename: Donald L
authors.initials: DL
authors.lastname: Bliwise
authors.forename: Sophia A
authors.initials: SA
authors.lastname: Greer
authors.forename: Albert P
authors.initials: AP
authors.lastname: Sigurdsson
authors.forename: Gudbjörg Birna
authors.initials: GB
authors.lastname: Gudmundsdóttir
authors.forename: Thomas
authors.initials: T
authors.lastname: Wessel
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Organisak
authors.forename: Thor
authors.initials: T
authors.lastname: Sigthorsson
authors.forename: Kristleifur
authors.initials: K
authors.lastname: Kristjansson
authors.forename: Thordur
authors.initials: T
authors.lastname: Sigmundsson
authors.forename: David B
authors.initials: DB
authors.lastname: Rye
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D005260:Female; D006801:Humans; D007206:Individuality; D016013:Likelihood Functions; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic; D020189:Nocturnal Myoclonus Syndrome / Q000175:diagnosis / Q000503:physiopathology*; D017286:Polysomnography; D012148:Restless Legs Syndrome / Q000175:diagnosis*; D012737:Sex Factors; D055815:Young Adult