We’ve all wondered how much sleep we should be getting each night. Last May, a review of unprecedented scale was published in Nature that has shined some new light on the subject. The review was conducted as part of the MULTI consortium – an ongoing project that aims to consolidate health data from several UK populations to study biological ageing and identify risk factors for disease.
In the study, the researchers assessed the relationship between sleep duration and biological ageing in a cohort of 500,000 middle-aged and older adults across the UK. Ageing was measured using 23 different biological ageing “clocks” covering 17 different organs, including medical imaging results (e.g., MRI) as well as the levels of specific proteins and metabolic biomarkers. For several of these biological clocks, a U-shaped relationship was observed between sleep duration and biological age gaps (i.e., the difference between a person’s chronological age and the biological age of their organs). Overall, the researchers found that 6-8 hours of sleep per day was associated with the lowest biological age gaps, which in turn was associated with reduced risk of disease and early death. Conversely, sleep durations below and above this “sweet spot” were associated with increased disease risk and accelerated ageing.
One of the other interesting findings of this review was that the ideal amount of sleep was not always the same for each of the body’s organs. For example, they found that protein markers in the heart suggested that 6 hours of sleep was associated with better cardiac health outcomes. Meanwhile, protein markers in the brain suggested that 8 hours of sleep was associated with better neurological and mental health outcomes. This supports the notion from previous studies on biological clocks that different organs can age at different rates. It also implies that you may be able to tailor your sleep to improve health outcomes for specific organs that are at the highest risk of disease. For example, people with genetic predispositions to heart disease may benefit more from a shorter sleep closer to 6 hours whilst those with predispositions to dementia may benefit more from a longer sleep closer to 8 hours.
It is important to note that although this study shows a correlational link between sleep duration and health outcomes, it does not prove a direct causational effect of sleep duration on health and biological ageing (i.e., does getting the right amount of sleep directly improve your health or do health conditions and ageing negatively impact your sleep?). Like many things in life, it is plausible that there is a bidirectional relationship between sleep and health, with both sleep influencing health and health influencing sleep. Further, the study does not necessarily prove that 6-8 hours of sleep is the optimum amount of sleep for every person as there are many factors that can influence how much sleep you need, including age and sex. Another limitation of the study is that sleep duration was self-reported via questionnaire rather than being objectively quantified via wearable sleep trackers or polysomnography sleep studies, thus the estimates of sleep duration may be skewed due to individual differences in sleep perception.
The key take-home message from this review seems to be that modifying sleeping patterns could be an effective way to improve overall health and longevity. Whilst it might not be easy to completely change your sleep overnight, there are some simple habits that can help improve your sleep hygiene. This includes maintaining consistent bed- and wake-times, reducing screen time before bed, and limiting time spent in bed without attempting sleep.
References
The MULTI Consortium., et al. (2026). Sleep chart of biological ageing clocks in middle and late life. Nature, Advance online publication. https://doi.org/10.1038/s41586-026-10524-5
The MULTI Consortium., et al. (2026). MRI-based multi-organ clocks for healthy aging and disease assessment. Nat. Med., 32, 82–92 https://doi.org/10.1038/s41591-025-03999-8
The MULTI Consortium., et al. (2025) Multi-organ metabolome biological age implicates cardiometabolic conditions and mortality risk. Nat. Commun., 16, 4871 https://doi.org/10.1038/s41467-025-59964-z
Wen J. (2025). Refining the generation, interpretation and application of multi-organ, multi-omics biological aging clocks. Nat. Aging, 5, 1897–1913. https://doi.org/10.1038/s43587-025-00928-9
