Nocturnal and daytime panic attacks - Comparison of sleep architecture, heart rate variability, and response to sodium lactate challenge

Background: The purpose of this study was to determine if nocturnal panic p atients have greater autonomic dysregulation than patients with daytime pan ic. Methods: Three groups were studied: patients who suffer from panic attacks during sleep (n = 12), those who stiffer from daytime panic attacks only (n = 12), and control subjects (n = 12), Each subject underwent 24-hour holte r monitoring for heart rate variability (HRV), an overnight sleep recording , and sodium lactate challenge during wakefulness, Results: There was a marked subjective response to the sodium lactate chall enge in the panic disorder (PD) patients but not in control subjects. Each group showed changes in HRV in response to sodium lactate challenge, The de crease in HRV measures was more marked in PD patients as a whole than in co ntrol subjects. During non-rapid eye movement (REM) sleep the value for fet al power (TP) was significantly higher in the nocturnal panic patients, The PD patients as a whole had higher values for TP and low-frequency (LF) pow er during REM sleep than control subjects. There were no significant differ ences between the two PD groups in sleep architecture. The PD patients as a whole had lower sleep efficiency and less stage 4 sleep than control subje cts. Conclusions: These findings indicate that there are substantial differences between PD and control subjects in autonomic regulation and that there are small differences between patients with daytime panic attacks and those wi th sleep-related panic attacks. Biol Psychiatry 1999; 45:1313-1320 (C) 1999 Society of Biological Psychiatry.