Sympathetic Overactivity Based on Heart-Rate Variability in Patients with Obstructive Sleep Apnea and Cerebral Small-Vessel Disease

Figures

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  Fig. 1. Flow chart for the selection of the study subjects. Among the patients who visited the Sleep Center of Ewha University Medical Center and underwent overnight PSG between April 2005 and May 2014, 185 patients were selected who underwent brain MRI within 1 year before or after PSG. Sixty-four of the 122 OSA patients had WMC. Thirty-three of the subjects without OSA did not have WMC. Subjects were excluded from the heart-rate variability analysis if the artifact-free and arousal-free periods of their N1, N2, or REM sleep periods were shorter than 5 min on PSG. Finally 135 subjects were included in the current study: 60 were assigned to the OSA+WMC group, 44 to the OSA−WMC, and 31 to the control group. OSA: obstructive sleep apnea, OSA+WMC: obstructive sleep apnea with white-matter changes, OSA−WMC: obstructive sleep apnea without white-matter changes, PSG: polysomnography, REM: rapid-eye-movement, WMC: white-matter changes.

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  Fig. 2. ApEn values during REM sleep in middle-aged OSA patients (age 45–64 years). A: ApEn values during REM sleep of each subject in the OSA−WMC group (0.94±0.23, n=18) and OSA+WMC group (0.79±0.25, n=18) (p=0.031, Mann-Whitney test). B: ROC curve analysis was performed for diagnosing OSA+WMC among middle-aged OSA patients. The area under the curve was 0.71. With a cutoff of ApEn <0.85, the sensitivity, specificity, PPV, and NPV were 55.6, 77.8, 71.4, and 63.6%, respectively. ApEn: approximate entropy, NPV: negative predictive value, OSA: obstructive sleep apnea, OSA+WMC: obstructive sleep apnea with white-matter changes, OSA−WMC: obstructive sleep apnea without white-matter changes, PPV: positive predictive value, REM: rapid-eye-movement, ROC: receiver operating characteristics.