Heart Rate Variability During Nocturnal Sleep and Daytime Naps in Patients With Narcolepsy Type 1 and Type 2

Purpose: Heart rate variability is a noninvasive measure of autonomic function. The aim of this study was to determine the risk of cardiovascular autonomic dysfunction during sleep in patients with narcolepsy. The effect of daytime napping was also examined in patients with narcolepsy type 1 and type 2. Methods: Polysomnography recordings and multiple sleep latency tests from 11 patients with narcolepsy type 1 (N1) and 20 patients with narcolepsy type 2 (N2) were included and compared with 12 healthy controls. Heart rate variability values (measured by time-and frequency-domain parameters) were calculated using electrocardiography data from the polysomnography-multiple sleep latency test recordings. Results: As an indicator of increasing sympathovagal imbalance, the low-frequency/high-frequency ratio was higher in all patients than in controls during non-rapid eye movement (NREM)-2 stage sleep (P <= 0.01). The root mean square of successive RR interval differences was lower (indicating parasympathetic tone) in N1 patients compared with N2 patients during REM sleep (P <= 0.04). In addition, decreased heart rate variability values were observed during sleep-onset REM-negative multiple sleep latency test periods compared with sleep-onset REM-positive periods. Conclusions: Heart rate variability abnormalities during sleep and the role of these changes on the development of cardiovascular diseases must be investigated in prospective follow-up studies of patients with narcolepsy. Heart rate variability changes during night sleep, daytime napping, and presence of sleep-onset REM periods may affect the lifethreatening events.