Heart rate variability in insomniacs and matched normal sleepers.
OBJECTIVE
It was hypothesized that psychophysiological insomniacs, who have been shown to have elevated heart rate, body temperature, and whole body metabolic rate, would also have increased low frequency and decreased high frequency power in the spectral analysis of their heart period data.


METHODS
Groups of 12 objectively defined insomniacs and age-, sex-, and weight-matched controls with normal sleep were evaluated on sleep and EKG measures over a 36-hour sleep laboratory stay.


RESULTS
Heart period was decreased (ie, heart rate was increased) and its SD was decreased in all stages of sleep in the insomniacs compared with the controls. Spectral analysis revealed significantly increased low frequency power and decreased high frequency power in insomniacs compared with controls across all stages of sleep.


CONCLUSIONS
Because increased low frequency spectral power is an indicator of increased sympathetic nervous system activity, these data imply that chronic insomniacs could be at increased risk for the development of disorders, such as coronary artery disease, that are related to increased sympathetic nervous system activity.
Dayton VA Hospital, Wright State University, and Kettering Medical Center, OH 45428, USA. bonnet.michael@dayton.va.gov
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D000328:Adult; D004562:Electrocardiography; D004576:Electromyography; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010092:Oximetry; D007319:Sleep Initiation and Maintenance Disorders / Q000175:diagnosis / Q000523:psychology*; D012895:Sleep, REM / Q000502:physiology*