Increased Heart Rate Variability but Normal Resting Metabolic Rate in Hypocretin/Orexin-Deficient Human Narcolepsy

Abstract

Scientific inveStigAtionSStudy objectives: We investigated autonomic balance and resting metabolic rate to explore their possible involvement in obesity in hypocretin/orexin-deficient narcoleptic subjects. Methods: Resting metabolic rate (using indirect calorimetry) and variability in heart rate and blood pressure were determined in the fasted resting state. Subjects included 15 untreated, hypocretin-deficient male narcoleptics and 15 male controls matched for age and body mass index. Results: Spectral power analysis revealed greater heart rate and blood pressure variability in hypocretin-deficient male narcoleptic patients (heart rate: p = 0.01; systolic blood pressure: p = 0.02; diastolic: p < 0.01). The low to high frequency ratio of heart rate power did not differ between groups (p = 0.48), nor did resting metabolic rate (controls: 1767 ± 226 kcal/24 h; patients: 1766 ± 227 kcal/24h; p = 0.99). conclusions: Resting metabolic rate was not reduced in hypocretindeficient narcoleptic men and therefore does not explain obesity in this group. Whether the increased heart rate and blood pressure variability-suggesting reduced sympathetic tone-is involved in this regard remains to be elucidated.

Body weight and basal metabolic rate in childhood narcolepsy: a longitudinal study

“…A few studies found that resting energy expenditure was reduced in patients with narcolepsy [17,28]. However, other studies demonstrated that the BMR did not significantly differ between patients and healthy controls [16,18]. These inconsistent results may be related to the small sample size in these studies, or to differences in patients' ages or disease durations.…”

Narcolepsy and sleep‐disordered breathing

“…When narcoleptics with a BMI < 30 kg/m 2 were studied separately, the BMR and EE were lower than that of BMI-matched controls [29]. Other studies have shown no difference [30].…”

Physiology of the orexinergic/hypocretinergic system: a revisit in 2012

“…Orexins affect the wakefulness pattern and physical activity, which are parameters not fully considered in these studies. By extrapolating these data, one might predict that human narcoleptics would have a lower metabolic rate, but that does not seem to be the case (107).…”