Fluff up the pillows and pull up the covers. 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, 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 author Sheldon Cohen, who studies the effects of stress on health at Pittsburgh's Carnegie Mellon University.
Prior research has suggested that sleep boosts the immune system at the cell level. This is the first study to show small sleep disturbances increasing the risk of getting sick, said Dr. Michael Irwin, who researches immune response at the University of California, 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.
Up against the virus
During cold season, staying out of range of sneezing relatives and co-workers may be impossible. The study, appearing Monday in the Archives of Internal Medicine, mimicked those conditions by exposing participants to a common cold virus — rhinovirus — and most became infected with it.
But not everyone suffered cold symptoms.
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 if they felt rested in the morning.
Then they checked into a hotel where 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.
Weight of tissues
Researchers measured their runny noses by weighing their used tissues. They tested for congestion 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 greater risk of catching a cold. Those who tossed and turned more than 8 percent of their 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's not 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.
Prior research has tied lack of sleep to greater risk of weight gain, heart disease, high blood pressure, stroke and diabetes.
Dr. Daniel Buysse, a sleep researcher at the University of Pittsburgh, said spending too much time in bed can lead to more interrupted sleep, which in this study "seems to be even worse than short sleep" for increasing the risk of catching a cold.
If it takes a long time to fall asleep or if you are restless during the night, "you would probably benefit from spending a little LESS time in bed," Buysse said in an e-mail. "If you fall asleep instantly, have no wakefulness during the night, and are sleepy during the day, you would probably benefit from spending a little MORE time in bed."
Buysse was not directly involved in the research, although he commented on an early draft of the study. The study was funded by grants from the National Institutes of Health and the MacArthur Foundation.
Harvard sleep researcher Sat Bir Khalsa said people do not need to turn to prescription sleep aids to improve their sleep. Setting a regular bedtime, moving computers and televisions out of the bedroom and, when restless, getting out of bed for a while and doing something soothing can help. His research focuses on treating insomnia with yoga.
As preventive measures, vitamin C and herbal supplements have not lived up to their reputation in rigorous studies. Cohen said research has shown people who get more exercise, drink moderately and have lower stress also get fewer colds.