TY - JOUR
T1 - Inter-movement interval as a primary stable measure of periodic limb movements of sleep
AU - Skeba, Patrick
AU - Hiranniramol, Kasidet
AU - Earley, Christopher J.
AU - Allen, Richard P.
N1 - Publisher Copyright:
© 2015 Elsevier B.V.
PY - 2016
Y1 - 2016
N2 - Aim: Periodic leg movements in sleep (PLMS) are generally evaluated by the number of events per hour during sleep, but this is an unstable measure with marked nightly variability and also fails to assess the basic periodicity that essentially characterizes these movements. The inter-movement interval (IMI) evaluates a putative biological process producing the period of PLMS. By contrast, the actual number of PLMS reflects the expression of this biological process that would likely be affected by multiple factors, particularly those disrupting sleep. Thus, this study tests the hypothesis that measurement of IMI duration should be more stable over nights in comparison to any measure based on counting the number of movements. IMI approximates a log-normal distribution. This study, therefore, tests the hypothesis that the means of the log IMI are more stable from night 1 (N1) to night 2 (N2) sleep recordings compared with measures of the number of PLMS. Methods: PLMS/h and IMI were measured for two consecutive nights of full sleep recordings for 29 restless legs syndrome (RLS) patients not being treated and 22 healthy controls without RLS. N1-N2 difference between nights was measured as percent of average for the nights. Results: Mean log IMI showed little nightly variability (mean ± SD for RLS: 3.6% ± 3.7, controls: 7.1% ± 7.0) significantly less p < 0.001) in comparison to PLMS/h (mean ± SD for RLS: 43.2 ± 37.1, controls: 63.7 ± 40.8). The IMI nightly variability was also significantly better than that for the periodicity index. IMI also varied considerably between individuals. Conclusion: Mean log IMI is a remarkably stable measure across nights within a subject and shows differences between subjects that may have clinical and biological significance. Because of this consistency, the mean log IMI should be considered as one standard measure of PLMS alongside the PLMS index.
AB - Aim: Periodic leg movements in sleep (PLMS) are generally evaluated by the number of events per hour during sleep, but this is an unstable measure with marked nightly variability and also fails to assess the basic periodicity that essentially characterizes these movements. The inter-movement interval (IMI) evaluates a putative biological process producing the period of PLMS. By contrast, the actual number of PLMS reflects the expression of this biological process that would likely be affected by multiple factors, particularly those disrupting sleep. Thus, this study tests the hypothesis that measurement of IMI duration should be more stable over nights in comparison to any measure based on counting the number of movements. IMI approximates a log-normal distribution. This study, therefore, tests the hypothesis that the means of the log IMI are more stable from night 1 (N1) to night 2 (N2) sleep recordings compared with measures of the number of PLMS. Methods: PLMS/h and IMI were measured for two consecutive nights of full sleep recordings for 29 restless legs syndrome (RLS) patients not being treated and 22 healthy controls without RLS. N1-N2 difference between nights was measured as percent of average for the nights. Results: Mean log IMI showed little nightly variability (mean ± SD for RLS: 3.6% ± 3.7, controls: 7.1% ± 7.0) significantly less p < 0.001) in comparison to PLMS/h (mean ± SD for RLS: 43.2 ± 37.1, controls: 63.7 ± 40.8). The IMI nightly variability was also significantly better than that for the periodicity index. IMI also varied considerably between individuals. Conclusion: Mean log IMI is a remarkably stable measure across nights within a subject and shows differences between subjects that may have clinical and biological significance. Because of this consistency, the mean log IMI should be considered as one standard measure of PLMS alongside the PLMS index.
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U2 - 10.1016/j.sleep.2015.10.004
DO - 10.1016/j.sleep.2015.10.004
M3 - Article
C2 - 26847989
AN - SCOPUS:84963664637
SN - 1389-9457
VL - 17
SP - 138
EP - 143
JO - Sleep Medicine
JF - Sleep Medicine
ER -