U. S. researchers reported on Monday that people who get less than seven hours of sleep a night three times more likely to catch a cold than those who sleep their complete quota.

The study conducted by Sheldon Cohen and colleagues at Carnegie Mellon University in Pittsburgh was the first to show that less than seven to eight hours of sleep in a night can lower your resistance to the common cold virus.

"Although sleep's relationship with the immune system is well-documented, this is the first evidence that even relatively minor sleep disturbances can influence the body's reaction to cold viruses," study lead author Sheldon Cohen, a psychology professor at Carnegie Mellon University in Pittsburgh said in a statement.

"It provides yet another reason why people should make time in their schedules to get a complete night of rest."

The study reported in the Archives of Internal Medicine said that patients who slept longer and more soundly were better able to resist infections than those who slept less or were more apt to toss and turn while in bed.

"Regular sleep habits may play an important role in your immune system's ability to fight off infectious disease," said Cohen. "Longer sleep duration and better sleep efficiency are both associated with greater resistance to the common cold."

The researchers tested 153 healthy participants who were asked there sleep patterns and how rested they felt. They were infected with a cold virus via nose drops and then locked in a hotel for five days. They were tested for cold symptoms and 28 days later underwent blood tests for antibodies to the virus and the researchers also collected mucus samples to test for the virus.

The participants who slept less than seven hours a night were found to be 2.94 times more likely to develop sneezing, sore throat and other cold symptoms than those who reported getting eight or more hours of sleep each night. "And those who lose more than 8 percent of sleep on an average night because they have trouble getting to sleep or wake up in the middle of the night are more than five times more likely to get a cold when exposed to a virus," Cohen said.

Dr. David L. Katz, director of the Yale University School of Medicine Prevention Research Center said, "Getting good sleep should count among the priorities of health-conscious people. Time invested in sleep will almost certainly be paid back in dividends of better health -- fewer colds and greater productivity."

The researchers feel the reason could be that disturbed sleep could affect immune system signaling chemicals called cytokines or histamines.

"Experiments that explore the relationship between sleep and immune function often involve sleep deprivation or study subjects with sleep disorders, which are often rooted in psychiatric conditions that influence other aspects of health," Cohen added. "This research points to the role played by ordinary, real-life sleep habits in healthy persons."