A major new study has found that both too little and too much sleep are associated with faster biological ageing across multiple organs, highlighting the potential importance of healthy sleep duration for maintaining overall health.

Published in the journal Nature, the study was led by Junhao Wen, assistant professor of radiology at Columbia University Vagelos College of Physicians and Surgeons. Researchers analysed data from nearly 500,000 participants in the UK Biobank and used machine learning to develop 23 biological “ageing clocks” covering 17 organ systems.

The researchers found a U-shaped relationship between sleep duration and biological ageing. Both very short and very long sleep were associated with faster ageing, while the lowest levels of biological ageing were observed among people who reported sleeping between 6.4 and 7.8 hours a day.

Key findings included:

• Fewer than 6 hours of sleep was associated with faster biological ageing.
• More than 8 hours of sleep was also associated with faster ageing.
• The lowest level of biological ageing was observed among those sleeping 6.4 to 7.8 hours.
• The associations were observed across multiple organs and biological systems.

The researchers said the findings do not mean that sleep duration alone determines how quickly a person's organs age. Instead, unusual sleep patterns may also serve as markers of underlying health problems.

Sleep linked to several health conditions

The study found that shorter sleep was associated with a range of health conditions, including depression, anxiety, obesity, type 2 diabetes, hypertension, ischemic heart disease and heart arrhythmias.

Both short and long sleep were associated with respiratory conditions such as chronic obstructive pulmonary disease and asthma, as well as digestive problems including gastritis and gastroesophageal reflux disease.

Looking at depression and biological ageing

The researchers also examined the relationship between sleep and late-life depression. Their analysis suggested that biological ageing in certain organs could play a role in the relationship between sleep duration and depression. However, the study could not establish whether abnormal sleep contributes to depression or whether depression affects sleep patterns.

What the study does-and does not-show

The study was observational, meaning it can identify associations but cannot prove that sleeping too little or too much directly causes faster ageing or disease. Other underlying health and lifestyle factors may contribute to both sleep patterns and biological ageing.

The researchers said the broad associations across the body suggest that sleep is closely connected with the coordinated functioning of the brain, immune system and metabolism. The findings could help guide future research into how sleep management may influence healthy ageing and disease risk.

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