Abstract
Introduction Several previous studies have reported that individual PLMS activities are associated with autonomic nervous system activity occurring shortly before each PLMS activities. However, there is no study investigating dynamic changes of autonomic nervous system activity before onset of PLMS. The aim of this study is to detect changes in heart rate variability (HRV) at the onset of the period in which periodic leg movements during sleep (PLMS) are observed using complex demodulation method. Materials and methods This study enrolled 14 patients diagnosed as having idiopathic PLMS disorder (PLMD). HRV-variables and spectral power of fluctuation of mean frequency in a high frequency band (HF-fluctuation; HFF) during sleep stage 2 were analyzed and compared between the period with and without PLMS. In addition, the changes of above parameters in periods in transition from the period without PLMS to that with PLMS were explored. Results Spectral power in the low frequency (LF) band and very low frequency (VLF) band were higher in the period with PLMS. Additionally, the average frequency in HFF was higher and the frequency in this band fluctuated during the period with PLMS with remarkable elevation of HFF. Moreover, the spectral powers in HFF, LF, and VLF were remarkably elevated shortly before the beginning of the period with PLMS (HFF, −65 s; LF, −53 s; and VLF, −45 s). Conclusion The elevation of sympathetic nervous activity and the HF frequency fluctuation can occur several tens of seconds before the beginning of the period with PLMS. Dynamic changes in the autonomic nervous system activity could be related with the vulnerability to PLMS occurrence during a night. Acknowledgements This study was supported by an Intramural Research Grant ( 21B-4 ) for Neurological and Psychiatric Disorders of NCNP, Fellowship for Young Clinical Sleep Researchers of the Japan Sleep Research Society , and MEXT/JSPS KAKENHI (Grant-in-Aid for Young Scientists, Grant Number: 24791235 ).
Highlights
Several reports have described that individual periodic leg movements during sleep (PLMS) activities are associated with autonomic nervous system activity occurring shortly before each PLMS activity
This study was conducted to explore the changes in heart rate variability (HRV) in transition from the period in which PLMS are absent to the period with frequent PLMS using timefrequency domain analysis, and complex demodulation method, which has high temporal resolution to delineate time-dependent fluctuations in both the amplitude and frequency of non-stationary and long-period data [17,18]
The inclusion criteria applied to patients were the following: 1) diagnosed as idiopathic PLMS disorder (PLMD) according to the International Classification of Sleep Disorders Second Edition [19]; 2) apnea–hypopnea index < 5/hr; 3) absence of any pathological arrhythmia; 4) absence of any muscular or neurologic disease; and 5) not taking medication that might affect autonomic nervous system activity (Table 1)
Summary
Several reports have described that individual periodic leg movements during sleep (PLMS) activities are associated with autonomic nervous system activity occurring shortly before each PLMS activity. No study has investigated dynamic changes of autonomic nervous system activity before the onset of PLMS. This study detected changes in heart rate variability (HRV) at the onset of the period with PLMS using complex demodulation method. This study was conducted to explore the changes in HRV in transition from the period in which PLMS are absent to the period with frequent PLMS using timefrequency domain analysis, and complex demodulation method, which has high temporal resolution to delineate time-dependent fluctuations in both the amplitude and frequency of non-stationary and long-period data [17,18]
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