Sleep state instabilities in patients with periodic limb movements in sleep - Detection and quantification with heart rate variability

Abstract

Background: Restless legs syndrome (RLS) has been thought to increase the risk of hypertension, cardiovascular events, and all-cause mortality. Periodic limb movements in sleep (PLMS) can be observed in most patients with RLS. Using non-invasive physiologic measurement and analysis, including heart rate variability (HRV) analysis, we aimed to investigate sleep quality and sleep state stability. Method: A total of 53 healthy controls and 15 patients with RLS and PLMS were recruited. Patients with other sleep-related disorders such as obstructive sleep apnea (OSA) and major depressive disorder (MDD) were excluded. Each subject was evaluated using sleep and mood questionnaires and had to undergo polysomnography (PSG). HRV analysis was applied to assess autonomic function and analyze correlations with the severity of periodic leg movements (PLM). The power of different brainwaves was analyzed using electroencephalogram (EEG). Electromyogram (EMG) was also used to explore the temporal correlation between changes in HRV and leg movement events. Results: Compared with healthy controls, PLMS group had not only poorer perceived sleep and mood questionnaires scales but also reductions in parasympathetic-related HRV indices and increases in sympathetic-related HRV parameters. The changes were in proportion to the severity of PLM. Brainwaves and sleep stage which indicate “deep sleep” decreased in the PLMS group. There were no significant temporal correlations between changes in HRV and leg movement events. Conclusions: Our findings suggest that patients with RLS and PLMS have poorer subjective sleep and mood scales. Besides, objective sleep quality including HRV analysis and brainwaves analysis revealed reduced parasympathetic tone, increased sympathetic tone, and sleep disturbance, which reveal the possibility of a higher risk for secondary disease.