Getting roughly 6 to 8 hours of sleep each day has been linked with a longer life — at least in humans.Credit: Justin Paget/Getty
A sweeping analysis of sleep duration and signs of ageing in half a million adults has pinpointed a sweet spot — about six to eight hours of sleep each day — that is linked to a lower risk of early death and disease.
Getting either more or less sleep than that was associated with accelerated ageing, which was measured by nearly two dozen different biological ageing ‘clocks’ that aim to assess ageing’s impact on the body.
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The results, published1 in Nature on 13 May, do not mean that six to eight hours is the optimum amount of sleep for every person, nor do they prove that achieving that ‘Goldilocks’ range of sleep each day directly improves health or slows ageing. But the study does provide one of the most comprehensive snapshots of the interplay between sleep and ageing throughout the body.
The results bolster a hopeful hypothesis: that improving sleep duration might offer a tractable way to reduce the risk of age-related disease, says Abigail Dove, a neuroepidemiologist at the Karolinska Institute in Stockholm who was not associated with the study. “Sleep affects every organ of the body,” she says. “And sleep is somewhat modifiable. This is a tool that could help.”
Light sleeper
Previous research also examined the relationship between sleep duration and a person’s ‘biological’ age, as assessed by clocks based on data such as biomarker levels. One such study2 found a U-shaped relationship between sleep and ageing, in which the difference between a person’s biological age and their chronological age was lowest for study participants who slept about 7 hours per day. Ageing seemed to accelerate in people who slept much more or less than this.
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Junhao Wen, a computational neuroscientist at Columbia University in New York City, and a light sleeper who frequently wakes up in the night, wanted to learn more about the effect of sleep duration on specific organs and systems in the body. So, Wen and his colleagues turned to the UK Biobank, a long-term study of more than 500,000 people that includes health data such as lifestyle questionnaires, brain imaging and blood samples.
The team looked for genetic links to abnormal sleeping patterns, and found surprisingly few. “Sleep might be more environmental,” Wen says. “It’s a strong message for the public that this can be modifiable.”
Organ variation
Studies3 using biological ageing clocks have suggested that different organs in the body can age at different rates. Wen and his colleagues looked for links between sleep duration and 23 such clocks, representing ageing in 17 organs. The clocks were based on levels of proteins or metabolites, or on features of medical images.
