Poor sleep has long been linked to chronic illness and even premature death. The new study provides the first evidence connecting less sleep and the risk of infectious sickness, researchers said.
Aric Prather, assistant professor of psychiatry at the University of California-San Francisco said in an e-mail that he regularly hears friends or colleagues bragging about their ability to accomplish things on little sleep. "It is my hope," said Prather, the lead author of the study published online Monday and in the September issue of the journal Sleep, "that studies like this one will provide the necessary science to show conclusively that chronic short sleep has a health cost.”
Researchers found that lack of sleep was the most important factor in predicting the likelihood of someone catching a cold, more so than age, stress levels and whether someone was a smoker, factors that were previously associated with a cold risk.
The Centers for Disease Control and Prevention say insufficient sleep is a public health epidemic. One in five Americans gets less than six hours of sleep on the average work night, the least amount of sleep among six countries surveyed in 2013 by the National Sleep Foundation.
In the past, the few studies on sleep and infectious illness have relied on a person’s self-reported history of catching a cold, recollection of his or her sleep patterns, or both, Prather said.
In the new study, researchers recruited 164 volunteers and measured their normal sleep habits with a watch-like sensor for seven nights. Then they put the volunteers in a hotel and gave them a cold virus in nose drops for a week to see who got sick and who didn't. (The amount of virus was about the same as a natural exposure.)
They collected daily mucus samples to see if volunteers had been infected.
What they found was striking: Those who slept less than six hours a night the week before were 4.2 times more likely to catch the cold compared with those who got more than seven hours of sleep.
Prather said the study wasn’t designed to figure out the underlying biology between the lack of sleep and susceptibility to colds. Available data suggests insufficient sleep disrupts the immune system and makes it less able to fight off a virus, he said.
As for the six-hour threshold, he said the study’s findings are consistent with recent recommendations from the American Academy of Sleep Medicine and the Sleep Research Society that urge people to get at least seven hours of sleep for optimal health.