Modern fitness trackers and smart watches have made it easier than ever to track the amount and quality of sleep you are getting each night. Around one in three Britons struggle with poor sleep, with stress, smartphone use, and irregular schedules all blamed for the growing problem.
While the risks of insufficient sleep are well-documented, a new study has found that getting too much sleep could be equally harmful. Scientists discovered that people who slept fewer than six hours or more than eight hours exhibited signs of faster biological ageing. Moreover, the researchers suggest the ideal amount is approximately seven hours per night.
Individuals who reported sleeping between 6.4 and 7.8 hours per night showed fewer signs of ageing. Lead author Junhao Wen, assistant professor of radiology at Columbia University Vagelos College of Physicians, stated: "This does not mean that sleep duration alone causes organs to age faster or slower. But it does suggest that both insufficient and excessive sleep may be markers of poorer overall health across the body."
What Is Biological Ageing?
Unlike chronological age, biological ageing refers to the progressive decline in the body's physiological function, including the ability for cells to repair themselves, increasing the risk of disease and death. Biological age measures the functional age of tissues and organs influenced by genetics, environment, and lifestyle.
Using this metric, researchers from Columbia University Irving Medical Center in the United States collected data from half a million participants in the UK Biobank and employed artificial intelligence to determine signs of ageing in organs. The study, published in the journal Nature, utilised AI-powered "ageing clocks" to measure wear and tear in organs.
Researchers gathered data from medical images, organ-specific proteins, and molecules found in blood for each organ. "In the liver, for example, we have an ageing clock built with protein data, an ageing clock of metabolic data, and an ageing clock of imaging data," Wen explained. "This allows us to examine how sleep may affect ageing across different organs in the body."
The scientists then assessed the relationship between a person's sleep duration, as reported by each Biobank participant, and their biological ages from 23 ageing clocks across 17 organ systems.
Associations with Disease
Among brain-related disorders, short sleep was significantly associated with depressive episodes and anxiety disorders, consistent with other studies linking sleep and mental health. Short sleep was also associated with obesity, type 2 diabetes, hypertension, ischaemic heart disease, and heart arrhythmias. Both short and long sleep were linked to chronic obstructive pulmonary disease, asthma, and a cluster of digestive disorders, including gastritis and gastroesophageal reflux disease.
Wen noted: "The broad brain-body pattern is important because it tells us that sleep duration is a deeply embedded part of our entire physiology, with far-reaching implications across the body." Beyond predicting disease, the organ-specific ageing clocks are valuable for determining how sleep relates to specific conditions, as exemplified by Wen's examination of late-life depression. Researchers believe long sleep could influence depression through changes in the brain and body fat.
The findings add to growing evidence that sleep problems may silently damage the body long before symptoms appear. "Everyone is excited by these ageing clocks and their ability to predict disease and mortality risk," Wen said. "But to me, the more exciting question is, can we link ageing clocks to a lifestyle factor that can be modified in time to slow ageing?"
Previous studies have found that sleep is largely linked to ageing and the pathological burden of the brain. "Our study goes further and shows that too little and too much sleep are associated with faster ageing in nearly every organ, supporting the idea that sleep is important in maintaining organ health within a coordinated brain-body network, including metabolic balance and a healthy immune system," Wen added.
Recommendations for Better Sleep
Health experts recommend maintaining a regular sleep schedule, limiting screen time before bed, and avoiding caffeine late in the day to improve sleep quality. For adults, the National Health Service recommends getting between seven and nine hours of quality sleep per night. This amount is considered essential for maintaining good physical and mental health, allowing the body to rest, repair, and properly regulate mood and energy levels.
