Researchers Gaining More Understanding Of Sleep, Sleep Loss, Daytime Sleepiness And Fatigue In Healthy Adults

"Our previous research demonstrated that patients with excessive daytime sleepiness such as obese subjects and those with sleep problems, such as sleep apnea, had higher levels of interleukin-6 (IL-6) in the blood during the day. This new research shows that in young, healthy people who had no sleep problems, that IL-6 was elevated the next day when they were denied sleep," explains Alexandros Vgontzas, M.D., associate professor of psychiatry and a psychiatrist The Milton S. Hershey Medical Center. "We also know that excessive daytime sleepiness occurs in about 5 percent of the population, so a better understanding of the mechanisms of sleep could help millions of people."

Il-6 is a cytokine. Cytokines are proteins that act as regulators in immune function, metabolism and sleep.

Vgontzas and his colleagues' paper titled, "Circadian Interleukin-6 Secretion and Quantity and Depth of Sleep," is published in the August issue of The Journal of Clinical Endocrinology and Metabolism.

Vgontzas and his team studied eight healthy young men between the ages of 20 and 29. They were all in general good health, physically active but not excessively, had no sleep complaints and were not taking any medications. Each subject took part in the experiment that lasted seven days. Each subject spent four consecutive nights in the sleep lab and was able to have a normal night of sleep. Blood was taken every half-hour for 24 hours to measure IL-6. On the fifth night subjects were made to stay up and not sleep at all. They were allowed to sleep again on nights six and seven.

"As we had thought, the amount of IL-6 in the blood was greatly increased during the day following the missed night of sleep. Subjects secreted the IL-6 during the day rather than at night. Their bodies wanted to sleep so they experienced daytime fatigue," explains Vgontzas.

Another finding of the study was that light sleep was associated with increased amount of IL-6 during the day while a good night's sleep was associated with decreased day time secretion of IL-6 and a good sense of well being. This finding means that good sleep is associated with decreased exposure of tissues to the potentially harmful actions of IL-6 on the cardiovascular system and bones. In addition, this study demonstrated that healthy people with greater amounts of deep sleep are inherently more capable of tolerating sleep loss, possibly avoiding exposure to the potentially harmful effects of increased IL-6 secretion.

The National Institutes of Health and Penn State's College of Medicine sponsored this work.

Vgontzas and his team plan further sleep studies into IL-6, including testing agents that might neutralize the secretion of IL-6.