The conversation about sleep and health has long been centered on the brain but a new study tracking nearly 500,000 people suggests the rest of the body is keeping score too. A study of nearly 500,000 adults in the UK Biobank has found that sleeping either too little or too much is associated with accelerated biological ageing across multiple organ systems not just the brain with the lowest estimated ageing burden falling between roughly 6.4 and 7.8 hours of sleep, depending on the organ and sex.
Sleep’s link to health has been studied for decades, but most prior work focused on single outcomes or relied on simple clinical measures. Biological ageing clocks tools that estimate how old a person’s organs and tissues are, based on imaging, proteins, or metabolites have opened a more granular way to track health. Researchers wanted to know whether the pattern of sleep affecting biological age extends consistently across the body, and whether it can be seen at the molecular level.
Earlier studies had already noted a U-shaped relationship between sleep duration and a few phenotype-based ageing clocks, meaning both very short and very long sleepers appeared older biologically than those sleeping a moderate amount. What had not been established was whether this pattern holds across multiple organ systems simultaneously — in brain, liver, lungs, skin, and elsewhere — or across multiple types of biological measurement in the same large sample.
The study, published in Nature in May 2026 by researchers from the MULTI Consortium and led by Junhao Wen at the New York Genome Center, used data from the UK Biobank, a population cohort of approximately 500,000 UK adults between the ages of 37 and 84. Sleep duration was measured at enrollment via self-reported questionnaire. Participants were asked how many hours of sleep they got in every 24 hours, including naps.
The researchers worked with 23 “biological age gap” (BAG) clocks — measures of how much older or younger a person’s biology appears relative to their chronological age. Seven were derived from multi-organ MRI data (structural imaging of the brain, heart, liver, pancreas, spleen, adipose tissue, kidney, and eye). Eleven came from plasma proteomics — the profile of proteins circulating in blood — and five from plasma metabolomics. To model the relationship between sleep and each clock, the team used generalized additive models, a method that can detect curved relationships without assuming in advance what the curve looks like.
For 9 of the 23 biological age clocks, a statistically significant U-shaped pattern emerged: both short sleep (under 6 hours) and long sleep (over 8 hours) were associated with higher biological age gaps compared to moderate sleep. The pattern appeared across organ systems and measurement types. Among the protein-based clocks, the brain showed the strongest signal. Significant U-shaped associations were also found for the lungs, liver, immune system, and skin. In the imaging-based clocks, significant associations appeared for the brain, adipose tissue, and pancreas. The endocrine metabolomics clock also showed a significant U-shaped pattern.
The sleep duration associated with the lowest biological age gap varied by organ and sex, falling between 6.4 and 7.7 hours for men and 6.5 to 7.8 hours for women across the nine significant clocks. For example, the brain protein-based clock showed its lowest values around 7.7–7.8 hours, while the brain imaging-based clock reached its lowest point near 6.4–6.5 hours. The researchers note that this discrepancy might reflect the different biological processes each measurement type captures, or could partly reflect reverse causality — where brain ageing causes longer sleep rather than the reverse.
The team also examined whether short and long sleep were associated with future disease and death. Using ICD-10 coded diagnoses and survival data in the UK Biobank, they found 153 significant associations between abnormal sleep duration and incident disease across organ systems. Short sleep showed a wider range of associations — spanning cardiovascular conditions, metabolic disorders including type 2 diabetes, musculoskeletal problems, respiratory conditions, and psychiatric diagnoses including depression and anxiety. Long sleep’s associations were more concentrated in brain-related and psychiatric conditions. Both short and long sleep were associated with increased risk of all-cause mortality: short sleep carried a hazard ratio of 1.50 (95% CI: 1.44–1.55) and long sleep a hazard ratio of 1.40 (95% CI: 1.36–1.44), each compared to the 6–8 hour reference group.
The study also examined how sleep might connect to late-life depression specifically. Using structural equation models, the researchers found that short sleep’s link to late-life depression was mostly direct — not substantially mediated through biological age clocks. Long sleep’s link, however, was largely indirect, running through accelerated brain and adipose tissue ageing. The authors suggest this distinction may mean short sleep acts through more immediate physiological stress pathways, while long sleep may reflect or accompany underlying subclinical disease processes.
To assess whether disease might cause disrupted sleep rather than the other way around, the researchers performed Mendelian randomization analyses — a method that uses genetic variants as proxies to test causal direction. These analyses did not provide strong evidence that disease causally drives sleep duration, but the researchers explicitly state they cannot rule out reverse causality entirely. They write that their study “cannot completely exclude such reverse causality.”
The researchers describe the study as, to their knowledge, the first to map the U-shaped relationship between sleep duration and ageing clocks across multiple organ systems and multiple omics data types simultaneously, and to connect this pattern to disease outcomes and mortality.
Several limitations apply. Sleep duration was self-reported, which introduces potential recall bias and does not capture sleep quality, timing, fragmentation, or circadian alignment. The primary design is cross-sectional for the biological age clock analyses — the imaging data were collected at a follow-up visit, while sleep was measured at baseline, but the study cannot establish temporal sequence definitively. Protein and metabolite measurements were taken at single time points, which may not accurately represent stable biological states. Nearly all participants were of European ancestry, limiting how broadly the findings apply. The replication attempted in two independent datasets was limited by small sample sizes (n = 385 and n = 573) in older populations. And while Mendelian randomization was used to probe causality, the paper acknowledges that evidence “cannot completely exclude such reverse causality.”
Reference:
The MULTI Consortium et al., “Sleep chart of biological ageing clocks in middle and late life,” Nature, published 13 May 2026. DOI: 10.1038/s41586-026-10524-5. Lead corresponding author: Junhao Wen, New York Genome Center (NYGC), New York, USA.
SUMMARY
Scientists pinpoint the sleep sweet spot—and your biological age appears to depend on it.
The number of hours you sleep each night is not just a lifestyle habit; it acts as a powerful regulator of how quickly nearly every organ system in your body grows old.
In one of the largest sleep analyses ever conducted, researchers examined data from more than 500,000 participants in the UK Biobank and compared sleep duration with 23 biological ageing clocks derived from brain imaging, plasma proteomics, and metabolomics. Findings reveal a startling U-shaped pattern: both short sleep (under six hours) and long sleep (over eight hours) were linked to accelerated ageing across the brain, heart, immune system, and metabolic networks. The lowest biological age gaps consistently appeared between 6.4 and 7.8 hours of sleep, indicating that the body operates with extraordinary resilience within this narrow restorative threshold. Research also demonstrated that abnormal sleep was associated with a higher risk of depression, diabetes, systemic disease, and all-cause mortality.
Junhao Wen and the MULTI Consortium leveraged multi-omics tools to show that sleep exerts a profound influence on the integrity of ageing pathways throughout the body. Wen noted that genetic analyses found surprisingly few strong inherited determinants, reinforcing that sleep is a modifiable behavior rather than a fixed predisposition. This insight is critical because it redefines sleep as an active mechanism for mitigating stressors and fostering long-term physiological agility. Experts at Columbia University argue that optimizing sleep may strengthen both mental and physical capacity in ways that extend far beyond simple fatigue reduction.
As we continue to navigate an era focused on longevity, this discovery proves that the most potent anti-ageing intervention may begin each night. Sleep is not passive downtime; it is a dominant biological process that coordinates repair, resilience, and systemic evolution. In a world searching for sophisticated tools to slow ageing, science is demonstrating that one of the most holistic interventions has been available all along—roughly seven hours of high-quality sleep.
