People who sleep six hours a night or less are four times more likely to catch a cold when exposed to the virus, compared to those who spend more than seven hours a night in slumber land, according to a new study by researchers in the United States.
The study, published in the academic journal Sleep, is the first to use objective sleep measures to connect people’s natural sleep habits and their risk of getting sick, according to Aric Prather, PhD, assistant professor of Psychiatry at UCSF and lead author of the study. The findings add to the growing evidence of the importance of sleep for our health, he said.
“Short sleep was more important than any other factor in predicting someone’s likelihood of catching a cold,” Dr Prather said. “It didn’t matter how old people were, their stress levels, their race, education or income. It didn’t matter if they were a smoker. With all those things taken into account, statistically sleep still carried the day.”
Insufficient sleep has been called a public health epidemic with links between poor sleep and automobile accidents, industrial disasters and medical errors. Working adults in western countries often get as little as six hours sleep a night.
Scientists have long known that sleep is important for our health, with poor sleep linked to chronic illnesses, disease susceptibility and even premature death.
Prather’s previous studies have shown that people who sleep fewer hours are less protected against illness after receiving a vaccine. Other studies have confirmed that sleep is among the factors that regulate T-cell levels.
Researchers recruited 164 volunteers between 2007 and 2011. The recruits underwent two months of health screenings, interviews and questionnaires to establish baselines for factors such as stress, temperament, and alcohol and cigarette use. The researchers also measured participants’ normal sleep habits a week prior to administering the cold virus, using a watch-like sensor that measured the quality of sleep throughout the night.
The researchers then put the volunteers in a hotel, administered the cold virus via nasal drops and monitored them for a week, collecting daily mucus samples to see if the virus had taken hold.
They found that subjects who had slept less than six hours a night the week before were 4.2 times more likely to catch the cold compared to those who got more than seven hours of sleep, and those who slept less than five hours were 4.5 times more likely.
“It goes beyond feeling groggy or irritable,” Prather said. “Not getting sleep fundamentally affects your physical health.”
The study shows the risks of chronic sleep loss better than typical experiments in which researchers artificially deprive subjects of sleep, said Prather, because it is based on subjects’ normal sleep behavior. “This could be a typical week for someone during cold season,” he said.
The discovery is viewed as yet another piece of evidence that sleep should be treated as a crucial pillar of public health, along with diet and exercise, the researchers said. But it’s still a challenge to convince people to get more sleep.
“In our busy culture, there’s still a fair amount of pride about not having to sleep and getting a lot of work done,” Prather said. “We need more studies like this to begin to drive home that sleep is a critical piece to our wellbeing.
