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One week of 2-Hour Sleep Deprivation Associated with Reduced Psychomotor Ability, Rise in IL-6, TNF-a: Presented at ENDO

By Paula Moyer

Special to DG News

SAN FRANCISCO -- June 24, 2002 -- Rises in inflammatory factors and decrease in performance are evident after one week of modest sleep deprivation, consisting of six hours of sleep per night.

Investigators presented these findings of this study, funded by the National Institutes of Health in the United States, at ENDO 2002, the 84^th annual meeting of the Endocrine Society.

They recruited 25 young healthy men and women who had no history of sleep disorders. The volunteers were recorded in the sleep laboratory for 12 consecutive nights. During the baseline period, the first four nights, the subjects were allowed to sleep for eight hours each night. They were awakened at 6:30 a.m. The baseline period was followed by one week of sleep restriction. During the sleep restriction period, subjects were awakened two hours earlier, at 4:30 a.m.

At baseline and following the sleep restriction week, the investigators obtained measures of daytime sleepiness, assessed by a multiple sleep latency test (MSLT); performance, assessed by a psychomotor vigilance test (PVT), and serial 24-hour plasma measures of IL-6, TNF-a, and cortisol.

After one week of sleep restriction, these subjects exhibited a significant increase of daytime sleepiness. The average sleep latency on MSLT was significantly decreased post-deprivation compared to baseline (p<0.05). The subjects also exhibited a significant deterioration of performance in four parameters of the PVT (p<0.05).

Following one week of sleep restriction, IL-6 secretion lost its normal bimodal secretion, which consists of a major peak at night and a secondary peak at approximately 7:00 to 8:00 p.m. Instead, the IL-6 secretion pattern consisted of a progressive rise from morning to evening, in parallel to the increasing sleep propensity. After the week of sleep restriction, TNF-a appeared to be elevated overall, although not at a level approaching statistical significance.

Although there was no difference in the amount of cortisol secreted or in the general 24-hour secretory pattern of cortisol, the late-evening cortisol zenith was moderately lower for men after sleep restriction than at baseline. There was no difference in the nadir. For women, there was no difference in the cortisol amount or pattern.

These findings "suggest that modest sleep loss appears to be a significant risk in terms of public safety, such as traffic accidents," the investigators reported. They expressed concern that, through the stimulation and alteration of IL-6, and the modest increase in TNF-a secretion, people with modest sleep debt may be at increased risk of major health hazards such as cardiovascular disease and osteoporosis.

"These data show that the difference between six and eight hours of sleep is not optional," said Alexandros N Vgontzas, MD, a professor of psychiatry at Penn State College of Medicine in Hershey, PA. "Two hours of sleep deprivation per night for one week is associated with increased somnolence, decreased performance, and activation of the inflammatory system, which is associated with several disorders, including atherosclerosis and cardiovascular disease."

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