People can stay healthier by sleeping ‘well not long’, a new study in the UK suggests.

Researchers found that people who felt they hadn’t slept well and struggled to get the recommended eight hours were two-and-a-half times more likely to go down with viruses like flu, colds and coronavirus.

But they also discovered that people who slept less could enjoy normal health as long as they felt they got good quality shut-eye.

The study is the first of its kind on the impacts of sleep-restriction on our immune systems and supports anecdotal evidence of people surviving perfectly well on little sleep.

Quantity or quality?

Professor Neil Walsh, of Liverpool John Moores University and lead researcher, said: “The debate on what makes a good night’s sleep has for a long time been around quantity, or the number of hours.

“The key might well be more about quality and in that sense, these findings change the way we should think about sleep and health.”

Most of us restrict our sleep to make way for our busy lives, whether to rise early for the morning commute or for childcare or to pursue busy social lives.

According to this new study published today (Wednesday, September 21) in the journal Sleep, adults restricting sleep by two or more hours each night are more likely to suffer respiratory illnesses but only in those reporting poor sleep quality. Adults reporting good sleep quality were protected against respiratory illness during sleep restriction.

Military 'wake up' calls

To delineate the restricted sleep, the team followed new recruits to the military, tracking their sleep patterns and health in the weeks before training and after signing up when forced to follow strict ‘to bed’ and ‘wake-up’ routines.

"Restricted sleep patterns can result in more frequent illness" - Professor Neil Walsh

The researchers recruited 1,318 healthy adults (68% males) and asked them to report their sleep duration and quality during civilian life and at the start and end of 12 weeks training. They defined sleep restriction as an individualized reduction in sleep of 2 hours or more per night vs civilian life. Respiratory infections were diagnosed by a doctor during training.

On average, recruits slept two hours less during military training than civilian life. Despite this, over half of those with sleep restriction rated their sleep as good quality.

Recruits who experienced sleep restriction during training were three times as likely to suffer respiratory infection. This finding remained after accounting for factors that influence respiratory infection incidence, like season and smoking.

Living with little sleep

A deeper dive into the data revealed a striking finding — sleep restriction only increased respiratory infection in recruits reporting poor sleep quality. Good sleep quality protected against respiratory infection during sleep restriction.

Professor Walsh, of the School of Sport and Exercise Sciences, added: “There are two very key messages here: firstly that restricted sleep patterns can result in more frequent illness, and secondly and more surprisingly, that we can live with restricted sleep as long as it is quality sleep.

“That is an extremely useful message in our hectic world where sleep is too often sacrificed for other pursuits.”

- Good perceived sleep quality protects against the raised risk of respiratory infection during sleep restriction in young adults is authored by Neil P Walsh, Daniel S Kashi, Jason P Edwards, Claudia Richmond, Samuel J Oliver, Ross Roberts, Rachel M Izard, Sarah Jackson, and Julie P Greeves.