Catching the common cold could be a sign you are not getting enough sleep. Credit: bikeriderlondon/Shutterstock

It’s no surprise that getting a good night’s sleep helps us avoid getting sick. Still, you might be surprised at just how much difference it makes. A new study finds that people who don’t get enough rest are four times more likely to come down with colds than those who do.

"Short sleep was more important than any other factor in predicting subjects' likelihood of catching [a] cold," Aric Prather, lead author of the study, said in a statement. The findings were published in the journal Sleep

The National Sleep Foundation's “International Bedroom Poll” reported in 2013 that 21% of Americans average less than six hours of sleep on week nights, and while for some people that may be sufficient, for many the consequences are disturbing.

The Centers for Disease Control and Prevention worry about the contribution lack of sleep is making to car accidents, industrial disasters, and medical and other occupational errors, while it has also been linked to an increased risk of cardiovascular disease. Prather’s research suggests we need to consider the contribution it makes to the spread of infectious diseases. "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,” Prather said. “With all those things taken into account, statistically sleep still carried the day."

While the spread of the common cold may make a substantial contribution to human misery the more worrying aspect of what Prather has found is how applicable it may be to more deadly conditions. Prather has previously reported that vaccines are less effective when given to people suffering sleep deprivation. In combination the studies suggest that inadequate sleep affects the immune system more than we have recognized.

The study was conducted in the laboratory of co-author Dr Sheldon Cohen of Carnegie Mellon University, where 164 healthy volunteers were monitored. Their sleeping patterns were recorded by wrist actigraphy for seven consecutive days before they were quarantined and administered nasal drops containing rhinovirus, which causes the common cold. The team then waited to see who got sick.

Those getting less than six hours' sleep in the previous week were 4.2 times more likely to succumb than those getting more than seven.

The problem may be exacerbated in the real world. People working long hours are likely to have colleagues doing the same, raising the risk that they will be exposed to infectious diseases in the first place. Worse still a person sufficiently dedicated to their job to be losing sleep for it may well also be inclined to show up when sick, thus infecting their workmates.

“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.”

Prather is currently undertaking a study of how sleep loss may explain the link between chronic stress and heart disease.