People who get too little sleep are more likely to catch a cold, according to US scientists who suspect that a good night’s sleep is crucial for the body’s immune defences.
Those who slept six hours a night or less were four times more likely to catch a cold when they were exposed to the virus than people who spent more than seven hours a night asleep, their study found.
The findings, reported in the journal Sleep, build on previous studies that suggest that the sleep-deprived are more susceptible to infectious diseases and recover more slowly when they do fall ill.
“It goes beyond feeling groggy or irritable,” said Aric Prather, a health psychologist at the University of California in San Francisco. “Not getting enough sleep affects your physical health.”
The scientists recruited 94 men and 70 women, with an average age of 30, for the study and subjected them to two months of health screening, interviews and questionnaires to establish their baseline stress levels, temperament and usage of alcohol and tobacco. The volunteers then spent a week wearing a wrist-mounted sleep sensor that tracked the duration and quality of their sleep each night.
To see how well they fought off infections, the participants were taken to a hotel and given nasal drops containing the cold virus. Doctors monitored them closely for a week after, collecting mucus samples to work out if and when the virus took hold.
The researchers found that the less sleep people got, the more likely they were to develop a cold. Those who got less than six hours of sleep a night were 4.2 times more likely to fall victim to the bug than those who slept more than seven hours. Those who slept less than five hours had a 4.5 times greater risk.
Prather said that when it came to defending against the cold virus, sleep was more important than any other factor they looked at, such as people’s stress levels, age, education, income, or whether they smoked. “With all those things taken into account, statistically sleep still carried the day and was an overwhelmingly strong predictor for susceptibility to the cold virus.”
He added that more studies into sleep and health were needed to drive home the message that sleep is critical for wellbeing, especially in a culture where some people pride themselves in not having to sleep and working late into the night.
The latest study could not say categorically that a lack of sleep made people more susceptible to viruses. It could be that another condition that makes people more likely to catch colds also disrupts their sleep. “Whether sleep interventions aimed at increasing sleep duration would protect individuals from cold incidence remains an open question,” the authors write.
Derk-Jan Dijk, professor of sleep physiology at the University of Surrey, said that sleep restriction has been shown to affect the immune system. “It is very plausible that a causal relationship exists,” he said. “The study is not conclusive but it adds to the growing evidence for the importance of adequate sleep duration in maintaining health.”
