Correlates of PLMs variability over multiple nights and impact upon RLS diagnosis

• Published in: Sleep medicine Vol. 10; no. 6; pp. 668 - 671
• Main Authors: Trotti, Lynn Marie, Bliwise, Donald L, Greer, Sophia A, Sigurdsson, Albert P, Gudmundsdóttir, Gudbjörg Birna, Wessel, Thomas, Organisak, Lisa M, Sigthorsson, Thor, Kristjansson, Kristleifur, Sigmundsson, Thordur, Rye, David B
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01-06-2009
• Subjects: Actigraphy; Adult; Analysis of Variance; Female; Gender differences; Humans; Individuality; Likelihood Functions; Male; Middle Aged; Monitoring, Physiologic; Neurology; Nightly variability; Nocturnal Myoclonus Syndrome - diagnosis; Nocturnal Myoclonus Syndrome - physiopathology; Periodic limb movements; Polysomnography; Restless legs syndrome; Restless Legs Syndrome - diagnosis; Sex Factors; Sleep Medicine; Young Adult; Actigraphy; Periodic limb movements; Restless legs syndrome; Gender differences; Nightly variability
• ISSN: 1389-9457; 1878-5506
• DOI: 10.1016/j.sleep.2008.06.009

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.