Chicago ? 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, of 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.

The study, appearing Monday in the Archives of Internal Medicine, exposed participants to a common cold virus — rhinovirus — and most became infected. 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.

Sleeping fitfully also was tied to greater risk of catching 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.

Prior research has tied lack of sleep to greater risk of weight gain, heart disease, high blood pressure, stroke and diabetes.