title: Correlation between putative indicators of primary restless legs syndrome severity.
abstract: OBJECTIVE
  Several methods of assessing disease severity in restless legs syndrome (RLS) have been suggested. The purpose of this study was to examine the relationship between the suggested immobilization test (SIT), the International RLS Study Group rating scale (IRLS), sleep efficiency, and periodic leg movements of sleep index (PLMI).
  
  
  METHODS
  Forty primary RLS patients with periodic leg movements of sleep were included in this prospective study. Study procedures were all performed during the same night, beginning with IRLS administration and following with SIT and polysomnography (PSG) evaluations, in that order. SIT was composed of two parameters: SIT mean discomfort score (SIT-MDS) and SIT periodic leg movements of wakefulness index (SIT-PLMW). PSG target measures were PLMI and sleep efficiency. Pearson's correlation was used for analysis at a P<0.01 significance level.
  
  
  RESULTS
  PSG-PLMI correlated with IRLS (r=0.462; P=0.003) and with SIT-PLMW (r=0.681; P=0.0004). A correlation was also found between IRLS and SIT-MDS (r=0.447; P=0.004), even though SIT-PLMW and IRLS did not correlate with each other (P=0.286). A negative correlation was found between PSG-PLMI and sleep efficiency (r=-0.435; P=0.005). Neither SIT nor IRLS correlated with sleep efficiency. Only SIT discomfort scores from the second half of SIT correlated with SIT-PLMW (r=0.457, P=0.004), and they had a stronger correlation with IRLS (P=0.003).
  
  
  CONCLUSIONS
  This study attempted a much needed comprehensive evaluation of the relationship between various RLS severity indicators. Our findings support a strong role of motor dysfunction on sleep quality in RLS, as well as the potential use of SIT-PLMW as a sensitive indicator of RLS severity.
authors.affiliation: Neurology Department, Erciyes University Medical Faculty, 38039 Kayseri, Turkey. aksu@erciyes.edu.tr
authors.forename: Murat
authors.initials: M
authors.lastname: Aksu
authors.forename: Sevda
authors.initials: S
authors.lastname: Demirci
authors.forename: William
authors.initials: W
authors.lastname: Bara-Jimenez
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015992:Body Mass Index; D004569:Electroencephalography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D020189:Nocturnal Myoclonus Syndrome / Q000175:diagnosis; D017286:Polysomnography / Q000379:methods; D011446:Prospective Studies; D012148:Restless Legs Syndrome / Q000175:diagnosis*; D012720:Severity of Illness Index