Correlates of PLMs variability over multiple nights and impact upon RLS diagnosis.
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.
Trotti
Lynn Marie
LM
Department of Neurology and Program in Sleep, Emory University, 101 Woodruff Circle-WMRB, Suite 6000, Atlanta, GA 30322, USA. lbecke2@emory.edu
Bliwise
Donald L
DL
Greer
Sophia A
SA
Sigurdsson
Albert P
AP
Gudmundsdóttir
Gudbjörg Birna
GB
Wessel
Thomas
T
Organisak
Lisa M
LM
Sigthorsson
Thor
T
Kristjansson
Kristleifur
K
Sigmundsson
Thordur
T
Rye
David B
DB
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