People who sleep less than seven hours a night appear to be almost three times as likely to catch a cold as those who sleep eight hours or more, a new study has found. Quality of sleep may count even more than quantity. Those who spend as little as 25 minutes a night tossing and turning face more than five times the risk of sniffing and sneezing. The age-old advice to get a good night's sleep is well-supported by medical research. Sleeping less than seven hours a night has been shown to increase the risk of high blood pressure, diabetes, weight gain and hardening of the arteries. Studies have also found that serious sleep deprivation disrupts the immune system. But those were experimental studies that kept subjects up for most of the night, then measured their immune responses. One of the surprising findings from the new study, published Monday in the journal Archives of Internal Medicine, was just how little it took to knock down defenses against the common cold. Very small disruptions in sleep, very small losses in terms of duration of sleep, were associated with pretty big increases in your probability of getting sick if you're exposed to a virus," said Sheldon Cohen, a professor of psychology at Carnegie Mellon University and the first author of the study. "It's not just insomniacs or people being deprived of sleep." Controlling for numerous factors that can influence health -- including age, race, income, education, smoking, exercise and depression -- the study found that the longer and better participants slept, the better they were able to resist or fight off infection, Cohen said.