HEART-RATE-VARIABILITY IN INSOMNIACS AND MATCHED NORMAL SLEEPERS

Objective: It was hypothesized that psychophysiological insomniacs, wh o have been shown to have elevated heart rate, body temperature, and w hole body metabolic rate, would also have increased low frequency and decreased high frequency power in the spectral analysis of their heart period data. Method: Groups of 12 objectively defined insomniacs and age-, sex-, and weight-matched controls with normal sleep were evaluat ed on sleep and EKG measures over a 36-hour sleep laboratory stay. Res ults: Heart period was decreased (ie, heart rate was increased) and it s SD was decreased in all stages of sleep in the insomniacs compared w ith the controls. Spectral analysis revealed significantly increased l ow frequency power and decreased high frequency power in insomniacs co mpared with controls across all stages of sleep. Conclusions: Because increased low frequency spectral power is an indicator of increased sy mpathetic nervous system activity, these data imply that chronic insom niacs could be at increased risk for the development of disorders, suc h as coronary artery disease, that are related to increased sympatheti c nervous system activity.