A study led by University of Warwick Professor Jianfeng Feng has found that regularly sleeping too little is associated with depression and brain loss in emotion areas, while sleeping too long is associated with cognitive decline and degenerative diseases.

Sleeping the right amount is crucial for long term health. 7 hours has recently been proposed as the average amount of sleep to aim for as an adult, yet some people regularly get too little, while others get more than they need.

‘How many hours of sleep do you have in every 24 hours?’

This question was asked to almost half a million 38–73 years aged adults from the UK Biobank database. The researchers in this study then classified them into those who slept fewer than 7 hours, a.k.a ‘short sleepers’, and those who slept more than 7 hours, a.k.a ‘long sleepers’. Their sleeping habits were then examined alongside data on their health outcomes, their genetic information and brain imaging data.

Professor Jianfeng Feng, School of Computer Science, The University of Warwick said: “Is short sleep and long sleep part of the same biological process, or are they distinct pathways with different effects on health? Answering these questions is crucial for developing targeted strategies to improve sleep health among aging populations.”

Their analysis found that regularly sleeping short durations is linked to psychological problems, such as low mood and fatigue, and poorer muscle and skeletal health (reduced vitamin D and IGF-1). Brain scans showed that short sleepers have reduced brain matter in brain areas involved in emotion, a biological consequence of cutting sleep short. Sleeping short durations was found to be a risk factor for a variety of conditions such as depression, heart disease and obesity.

Sleeping long hours, on the other hand, was associated with cognitive decline, higher inflammation and poorer metabolic health (lower ‘good’ cholesterol). Brain scans showed brain matter loss in areas associated with memory and known risk areas for degenerative disease. Long sleep was associated with diseases such as Alzheimer's and schizophrenia. However, sleeping long durations appears to be a symptom, rather than a cause, of these conditions.

Ultimately, genetic analysis showed long sleep and short sleep to be biologically distinct, with their own genetic associations, as opposed to viewing short sleep and long sleep as two extremes of the same process, which is more intuitive.

On the significance of this work, Professor Feng added: “This study represents a paradigm shift in how we understand the relationship between sleep and health. Short sleep is often an underlying cause of health issues, whereas long sleep tends to reflect pre-existing conditions. These findings highlight the importance of personalised interventions to address the unique biological pathways of short and long sleepers.

“Our ultimate goal is to construct a comprehensive sleep health profile across the human lifespan, providing actionable insights for individuals at every stage of life.”

This work will be important for establishing meaningful sleep management strategies for aging populations. Future work will expand this research out to more life stages and diverse populations.

The full Nature Mental Health paper can be accessed here: https://doi.org/10.1038/s44220-025-00395-6

ENDS

For more information, please contact:

Matt Higgs, Media & Communications Officer (Sciences)

Matt.Higgs@Warwick.ac.uk/+44 7880175403

Notes to Editors

The Study and Authors

The study was led by Professor Jianfeng Feng, Professor of Computer Science at The University of Warwick & Professor of Mathematics and Director of Computational Systems Biology Centre, Fudan University, Shanghai, China.

Significant contributions to this study were made from researchers from the Institute of Science and Technology for Brain-Inspired Intelligence, Fudan University. Specifically, from Professor Wei Cheng and Professors Tianye Jia, and postdoctoral researcher and first author Yuzhu Li.

This study was supported by the National Natural Science Foundation of China, the National Key R&D Program of China, and the Shanghai Municipal Science and Technology Major Project. The funders had no role in study design, data collection and analysis, decision to publish or preparation of the manuscript.

The University of Warwick

The University of Warwick is one of the UK’s leading universities, marking its 60th anniversary in 2025. With over twenty-eight thousand students from 147 countries, it's currently ranked 9th in the UK by The Guardian University Guide. It has an acknowledged reputation for excellence in research and teaching, for innovation, and for links with business and industry. The recent Research Excellence Framework classed 92% of its research as ‘world leading’ or ‘internationally excellent’. The University of Warwick was awarded Midlands University of the Year by The Times and Sunday Times.

The UK Biobank

The UK Biobank is a large-scale biomedical database and research resource containing de-identified genetic, lifestyle and health information and biological samples from half a million UK participants. It is the most comprehensive and widely used dataset of its kind and is globally accessible. This project corresponds to UK Biobank application ID 19542