January 20, 2009
CHICAGO (AP) – Preventing the common cold may be as easy as getting more sleep.
Researchers paid healthy adults $800 to have cold viruses sprayed up their noses and then wait five days in a hotel to see if they got sick. Habitual eight-hour sleepers were much less likely to get sick than those who slept less than seven hours or slept fitfully.
“The longer you sleep, the better off you are, the less susceptible you are to colds,” said lead researcher Sheldon Cohen, who studies the effects of stress on health at Pittsburgh’s Carnegie Mellon University.
Earlier research has suggested that sleep boosts the immune system at the cell level. But Cohen’s is the first study to show that small sleep disturbances increase the risk of getting sick, said Dr. Michael Irwin, who researches immune response at the University of California at Los Angeles and was not involved in the study.
“The message is to maintain regular sleep habits because those are really critical for health,” Irwin said.
During cold season, staying out of range of sneezing relatives and co-workers may be impossible. The study, whose findings appear in Monday’s edition of the Archives of Internal Medicine, mimicked those conditions by exposing participants to a common cold virus – rhinovirus – and most of them became infected with it.
But not everyone suffered cold symptoms.
The people who slept less than seven hours a night in the weeks before they were exposed to the virus were three times more likely to catch a cold than those who slept eight hours or more.
To find willing cold victims, researchers placed ads and recruited 78 men and 75 women, all healthy and willing to go one-on-one against the virus. They ranged in age from 21 to 55.
First, their sleep habits were recorded for two weeks. Every evening, researchers interviewed them by phone about their sleep the night before. Subjects were asked what time they went to bed, what time they got up, how much time they spent awake during the night and whether they felt rested in the morning.
Then the participants checked into a hotel, and the virus was squirted up their noses. After five days, the virus had done its work, infecting 135 of the 153 volunteers. But only 54 people got sick.
Researchers measured the volunteers’ runny noses by weighing their used tissues. Congestion was tested by squirting dye in the subjects’ noses to see how long it took to get to the back of their throats.
Sleeping fitfully also was tied to a greater risk of catching a cold. Those who tossed and turned more than 8 percent of the time in bed were five times more likely to get sick than those who were sleepless only 2 percent of the time.
Surprisingly, feeling rested was not linked to staying well. Cohen said he wasn’t sure why that is, other than feeling rested is more subjective than recalling bedtime and wake-up time.
Cold symptoms like congestion and sore throat are caused by the body’s fight against a virus, rather than the virus itself, Cohen said. People whose bodies make the perfect amount of infection-fighting proteins called cytokines will not even know they are fighting a virus. But if their bodies make too many, they feel sick.
Sleep may fine-tune the body’s immune response, Cohen said, helping regulate the perfect response.
