New research finds that people who sleep less than seven hours a night or toss and turn frequently may be more susceptible to the common cold.

New research finds that people who get less than seven hours of sleep per night may be more susceptible to the common cold.

The preliminary findings come from a study at Carnegie Mellon University, where researchers recruited about 150 healthy men and women to participate.

The volunteers agreed to keep track of how many hours they slept each night for two weeks. They also estimated how much time they spent tossing and turning.

Then researchers purposely infected the volunteers with a common cold virus called rhinovirus and watched to see who got sick.

They found that the people who had slept less than seven hours a night in the weeks before being exposed to the virus were about three times more likely to develop a full-fledged cold than those who had slept more.

What surprised researchers the most was a fairly strong association between interrupted sleep and the onset of cold symptons. It turned out that people who tossed and turned a lot or spent a lot of time in bed trying to fall asleep were also much more likely to get sick.

"We were surprised by the magnitude of the effect," says researcher Dr. Sheldon Cohen of Carnegie Mellon. Cohen's previous research has shown a strong association between stress and susceptibility to the common cold.

One weakness of the study is that it relied on volunteers to estimate their own sleep. Experts say more objective measures are needed to validate the findings.

"Clearly, it would be better to have a formal sleep study to verify that people are accurately reporting the amount of sleep they get," says Dr. Ron Turner of the University of Virginia, who collaborated with the Carnegie Mellon researchers.

Formal sleep studies are expensive. But scientists say they do plan follow-up research. One option is to use movement-sensing technology that tracks people's movements in bed.

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