Not getting enough sleep dramatically increases the chances of catching a cold, research has shown.
eople who sleep six hours a night are four times more susceptible to colds than those who sleep more than seven hours.
Scientists exposed 164 volunteers to the common cold virus to test their ability to fight off the infection.
They found that poor sleep in the previous week was associated with a 4.2 times increased risk of developing cold symptoms.
Those who slept for less than five hours a night were 4.5 times more likely to start sneezing.
"It goes beyond feeling groggy or irritable. Not getting sleep fundamentally affects your physical health," said lead researcher Dr Aric Prather, from the University of California at San Francisco.
Participants in the study had their normal sleep habits assessed during the week before the scientists attempted to make them catch a cold.
Nasal drops were used to administer the cold virus, after which the volunteers were monitored for another week.
"Short sleep was more important than any other factor in predicting subjects' likelihood of catching cold," said Dr Prather.
"It didn't matter how old people were, their stress levels or education. It didn't matter if they were a smoker. With all those things taken into account, sleep still carried the day."
The findings appear in the latest online edition of the journal Sleep.