Activity, Arousal, and the MSLT in Patients with Insomnia

OBJECTIVES: It has recently been shown that physiological arousal following walking increased sleep latencies during daytime naps as compared to sleep latencies following TV viewing. Patients with insomnia have been shown to have increased physiological arousal and to also have longer MSLT latencies. It was hypothesized that insomnia patients, who are at a higher state of physiological arousal, would be unable to relax while lying in bed and watching TV and therefore would have relatively longer sleep latencies in naps following TV watching (due to inability to relax) as compared to walking. DESIGN: Twelve patients with psychophysiological insomnia took Multiple Sleep Latency Tests after either watching television for 15 minutes or after a 5-minute walk following baseline, sleep deprivation, and recovery sleep conditions. SETTING: Sleep Laboratory PATIENTS: Twelve patients with psychophysiological insomnia INTERVENTIONS: Manipulation of state arousal and sleep deprivation RESULTS: Sleep latencies were significantly longer following the walk as compared to watching TV (11.9 vs. 6.9 min. respectively). Sleep latencies were 13.4 and 3.8 min. following baseline and sleep deprivation conditions. Heart period, used as a measure of physiological arousal, was significantly elevated throughout naps following the walk as compared to naps following TV viewing. Heart period was also significantly correlated with nap sleep latency. CONCLUSIONS: The insomnia patients in this study had significantly increased arousal, as measured by heart rate, and significantly longer sleep latencies after walking as compared to resting. The magnitude of these changes was similar to that seen in normal subjects in a previous study. These data, in concert with previous work, support the contention that measured sleep tendency is a combination of sleep drive and level of central nervous system arousal, where arousal has both state and trait components.