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Eight Hours a Night Keeps the Doctor Out of Sight

It's common wisdom that sleep is protective and restorative in battling illness, but research now under way may eventually show just how that process actually works. "We don't understand the mechanism," says Dr. Janet Mullington, a research fellow in the Department of Psychiatry, who is teasing out the relationship between sleep and the immune system in a series of experiments. "If we understand how this works, we can intervene."
To test the relationship between slow-wave sleep -- the early, restorative sleep phase -- and illness, Mullington and her colleagues set up an experiment to trick their subjects' immune systems and record their reactions. Right before bed, at 11 P.M., the subjects of the study were injected with endotoxins -- harmless lippopolysaccharides that trigger the body's immune system. The white blood cells, or macrophages, identify the endotoxins as bacteria and set off "all the bells" to fight the invaders. As the subjects go to sleep, those who received the lowest dose of endotoxins experience an increase in the slow-wave sleep, which Mullington describes as "the most powerful, most core sleep." The subjects who received higher doses of endotoxins, however, experience sleep disturbance, as well as a slight rise in temperature and sometimes other symptoms ranging from headaches to body aches and shivers. The "whole response is over in six hours," notes Mullington.
Not enough is yet known to understand why only the lower doses increase slow-wave sleep, but Mullington thinks that the timing of sleep and the onset of illness may be important. Perhaps, she speculates, "if you're coming down with something, sleep will have a preventative effect. Maybe you should have gotten your sleep at the beginning, when you get run down. Maybe you can head it off at the pass."
To further test her hypothesis and the complex relationship between sleep and sickness, Mullington is now investigating the relationship between sleep deprivation and the endotoxin challenge. Subjects are given the injection at 11 P.M. and then are not allowed to sleep all night. (Friends stay with them to help keep them awake.) Some subjects will be kept awake for two nights -- one before the injection and one the night after -- to test the effects of a sleep deficit before the onset of an illness. Results of the latest series of experiments should be available in a few months, Mullington says.

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