The quality of your sleep, rather than the quantity, is more important for your immune system.
That's according to new research from Liverpool John Moores University in the UK.
The US-based National Sleep Foundation advises that healthy adults need between seven and nine hours of sleep per night
But the British researchers found 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.
Lead researcher Professor Neil Walsh explained it to Moncrieff.
"We showed for the first time that if you restrict sleep by more than two hours, which many of us do in the working week, you are more likely to get respiratory infections like the cold, COVID, and flu.
"But there was a really important twist: what we showed when we looked much closer at the data, was that the increase in respiratory infections with sleep restriction were restricted to those who had poor sleep quality.
"Those young adults who had sleep restriction, but that had good quality sleep, were not at any increase risk of suffering infection at all".
'Individual sleep needs'
Prof Walsh said they used a simple comparative tool.
"We asked these young adults to rate their sleep quality on a 1 to 4 scale that's regularly used - from 'very poor' to 'very good'.
"We used a very simple questionnaire in lots and lots of people - over 1,000.
"And we showed that when somebody says they had good sleep, even if they had short sleep, that good sleep seems to protect them against common colds, flu, COVID and the like.
"Sleep is quite individual and we all have individual sleep needs.
"So I think our research sort of sheds light on that: that it's not just about quantity, the quality's important."
'Catching up' on sleep
However he said trying to play 'catch up' on lost sleep is not always effective.
"We do sleep short in the week, maybe we restrict by a couple of hours - we have to get up early in the morning for work, etc.
"Can we catch up at the weekend? There are now really good studies showing that's not very good for you in the long-term.
"That you think you can actually catch up, and you feel better after a bit more sleep at the weekend.
"But actually, systems like your immune system... they don't seem to work so well after many weeks of doing that".
Prof Walsh said there are five things people can do to ensure good sleep quality:
- Keep bedtime and waking times consistent, including on weekends
- Avoid eating large meals or drinking alcohol or caffeine close to bedtime
- Ensure your bed, pillow and surroundings are comfortable (keep your room cool and dark)
- Get into a relaxing bedtime routine (switch off mobile phones about 30 minutes before bed)
- Exercise during the day can help you fall asleep quicker
