In the first study of its kind, researchers from Carnegie Mellon University report that lack of sleep can increase your odds of catching a cold. In the study, people who slept less than seven hours a night were nearly three times as likely to catch a cold as people who slept eight hours a night or more. What’s more, people with low “sleep efficiency” – who reported spending less than 92 percent of their time in bed actually asleep – were more than five times as likely to come down with a cold as those whose sleep efficiency was 98 percent or more.

The study lends credence to the idea that sleep deprivation can impair the immune system, making it harder for people to fight off infection. Other studies have suggested that lack of sleep can increase the risk of heart disease, weight gain, high blood pressure, stroke, and diabetes.

In the study, researchers tracked 153 healthy volunteers with an average age of 37 for two weeks, calling them daily to ask about the amount and quality of sleep they had gotten the night before. Then, the volunteers had samples containing the rhinovirus, one of the more common causes of colds, squirted inside their nose and each checked into a hotel room for five days. Afterwards, the researchers tested them for infection with the virus and for symptoms of the common cold including sneezing, sore throat, runny nose, and congestion.

While nearly 90 percent of the volunteers became infected with the virus, only 35 percent got sick. Those who had slept fitfully or for fewer hours each night were much more likely to show symptoms than those who slept soundly for eight hours or more.

Cold symptoms are caused by the reaction of the body’s immune system to infection with a cold-causing virus, not by the infection itself. If a person’s immune system mounts a defense that is equal to the infection, it can fight off the virus that person even realizing they are fighting an infection. However, when the immune system is not able to control the infection early, it must mount a much larger response to rid the body of the virus, leading to the symptoms of a cold.

The researchers suggest that sleep may “fine tune” the immune system, allowing it to mount an appropriate immune response using signaling molecules called cytokines and histamines. Lack of sleep may hamper the immune system by interfering with these molecular signals.

According to the researchers, seven to eight hours of quality sleep each night is a reasonable goal to help people maintain a healthy immune system. One important finding of the study was that tossing-and-turning had an even greater impact on the ability to fight off a cold than sleep time. You can also improve the restfulness of your sleep by practicing good sleep hygiene such as setting a regular bedtime, not watching TV in bed, and getting out of bed when for a while when you can’t seem to sleep. Engage in something relaxing for a few minutes, and then get back in bed when you feel tired.

For more information on sleep hygiene, join the Healia Health Community on Sleep Disorders, and for more about the common cold, join the Healia Health Community for Cold and Flu.


_{Photo: deeleea, Flickr, Creative Commons}