Autonomic Response to Periodic Leg Movements during Sleep in Narcolepsy-Cataplexy

Study Objectives: To test the hypothesis of autonomic nervous system dysfunction in patients with narcolepsy-cataplexy (NC) by assessing the physiologic activations associated with periodic limb movements during sleep (PLMS). Design: Sleep and heart rate (HR) were recorded during 1 night of polysomnography. Setting: Data were collected at the Sleep Disorders Center, Sacre-Coeur Hospital, Montreal, Canada. Participants: Data from 14 patients with NC (6 men, 8 women, mean age: 52.5 +/- 11.9 years) were compared with data from 14 healthy control subjects matched for age and sex. Interventions: NA. Measurements and Results: Analyses included sleep stages, PLMS, microarousals, RR intervals converted into beats per minute on segments lasting 25 heartbeats (10 RR intervals before PLMS and 15 after), and cardiac-activation amplitudes. A Group-by-Heartbeat interaction was noted for PLMS without microarousals; the patients had a tachycardia of lower amplitude and a delayed and lower-amplitude bradycardia, compared with normal control subjects. Similar significant HR modifications were observed for PLMS with microarousals between patients with NC and control subjects. Patients with NC had a reduced magnitude of cardiac activation associated with PLMS with and without microarousals, as compared with control subjects. A negative correlation was noted between cardiac-activation amplitude and age in patients with NC, but no correlation with PLMS index was found in either patients with NC or control subjects. Conclusion: A significant reduction in the amplitude of PLMS-related HR responses in both tachycardia and bradycardia was found in patients with NC. These findings favor the physiologic relevance of the action of hypocretin on autonomic function that may be of clinical significance, i.e., increasing the risk of cardiovascular diseases.