Sleeping too few or too many hours each night may speed up ageing in the brain, heart, lungs, and immune system, a new study suggests. The research was published in Nature on May 13. It found that both short sleep and long sleep are tied to faster ageing in nearly every organ. The lowest risk was seen in people who slept between 6.4 and 7.8 hours per day.
Junhao Wen, assistant professor of radiology at Columbia University, led the study. "Our study shows that too little and too much sleep are associated with faster ageing in nearly every organ," he said. "This supports the idea that sleep is important in keeping the brain and body healthy."
To measure ageing, the team used machine learning to build 23 biological clocks for 17 organ systems. The clocks used data from medical scans, blood tests, and proteins to estimate how fast each organ was ageing compared to a person's real age.
The researchers analysed health data from half a million people in the UK Biobank. They found a U-shaped pattern. Both short sleep, under six hours, and long sleep, over eight hours, were linked to faster ageing. The healthiest range was around seven hours.
Short sleep was linked to depression, anxiety, obesity, type 2 diabetes, high blood pressure, and heart disease. Both short and long sleep were linked to lung problems like COPD and asthma, as well as stomach issues such as acid reflux.
Wen said the results show sleep is deeply connected to the whole body. "Sleep duration is part of our entire physiology, with far-reaching effects across the body," he said.
The team also looked at depression in older adults. Their analysis suggests short sleep may act directly on depression, while long sleep may affect it through changes in the brain and body fat. Wen said this means short and long sleepers may need different types of care.
The study does not prove that sleep alone causes faster ageing. But it suggests sleep habits could be an important target for protecting health as people get older.
