Fudan University Research: Sleeping too much or too little affects health, 7 hours is just right | World Sleep Day

As one of the basic needs of human health, the importance of sleep is self-evident. With the acceleration of the pace of modern life, people's sleep habits are becoming increasingly diverse, and sleep duration is also showing a polarized trend. In recent years, more and more studies have pointed out that abnormal sleep duration is closely related to a variety of health problems, especially in the middle-aged and elderly population. Too much or too little sleep may lead to cardiovascular disease, mental disorders and neurodegenerative diseases.

In order to further explore the specific relationship between sleep duration and health, especially whether short sleep and long sleep affect health through different biological mechanisms, Professor Feng Jianfeng of Fudan University and his team published their latest research in the journal Nature Mental Health, revealing the different effects of short sleep and long sleep on health, and finding out the causal relationship, thereby providing the public with more scientific sleep advice.

Research process and methods

The study was based on data from the UK Biobank and included more than 600,000 participants aged 38 to 73. In order to ensure the accuracy and reliability of the study, the study used a variety of advanced research means and methods.

The researchers divided the participants into a short sleep group (≤7 h) and a long sleep group (≥7 h) based on their sleep duration, and recorded the average sleep time of the participants in each group in detail. In order to deeply analyze the relationship between sleep duration and various health indicators, they obtained blood test data, metabolomics data, and neuroimaging results from some participants, in order to reveal the impact of sleep duration on physical health from different levels.

In the full phenotype group association analysis, the researchers explored the relationship between short sleep and long sleep and 3,735 phenotypic variables. This large-scale analysis helps to fully reveal the complex association between sleep duration and health problems.

In addition, the study also used a variety of advanced research methods, including genetic analysis, immune metabolism testing and brain structure imaging. They conducted in-depth research on the differences between short-sleeping and long-sleeping groups in genetics, immune metabolism and brain structure, and tried to clarify the causal relationship between sleep duration and health problems through methods such as Mendelian randomization analysis. The entire research process is rigorous and meticulous, aiming to reveal the mechanism of the impact of sleep duration on health from multiple levels.

Research Findings

After rigorous data analysis and in-depth research, the Fudan team made a number of important discoveries:

1. Differences in health effects between short sleep and long sleep: There are significant differences between short sleep groups and long sleep groups in genetics, immune metabolism and brain structure, which supports the view that the length of sleep affects health through different biological mechanisms.

2. Short sleep is the "cause" of disease: Studies have found that short sleep is more often the "cause" of disease. It is associated with insomnia, difficulty sleeping, depression, body pain, and increased number of drug treatments. At the same time, short sleep is also significantly associated with markers related to bone health and aging , such as alkaline phosphatase, vitamin D, and insulin-like growth factor. Therefore, short sleep is not only a potential health risk factor, but also a direct cause of many diseases and health problems.

3. Long sleep is the "fruit" of disease: In contrast, long sleep is more of a "result" of disease. It is associated with a variety of physical and psychological symptoms, such as frequent naps during the day, difficulty getting up in the morning, slower walking speed, and increased body fat percentage. In blood tests, long sleep is closely associated with markers of the immune system and inflammatory response, as well as markers of cardiovascular disease risk. At the same time, brain structure analysis found that the volume of the hippocampus and thalamus of long sleepers was significantly reduced, and these brain areas are the key areas responsible for memory and cognitive function, which means that long sleep may be related to cognitive decline and memory problems. Therefore, long sleep is a warning sign of poor physical health.

4. Sleep duration is associated with a decrease in overall health scores and an increase in long-term illness rates: Both short and long sleep are associated with a decrease in overall health scores and an increase in long-term illness rates, which further emphasizes the importance of maintaining an appropriate sleep duration.

5. Differences in genetic background: People who sleep different lengths of time have obvious differences in genetic background, which provides a theoretical basis for future sleep interventions for specific populations.

The latest research from the Fudan University research team shows that sleep duration is closely linked to health. Short sleep may be a risk factor for disease, and is associated with symptoms such as insomnia, depression, and body pain; long sleep indicates health problems, and is associated with consequences such as decreased immunity, cardiovascular disease, and cognitive impairment.

Sleep Tips

1. Maintain an appropriate sleep duration: Adults should try to maintain 7 hours of sleep per night and avoid sleeping too short or too long.

2. Pay attention to sleep quality: In addition to sleep duration, sleep quality is equally important. Try to create a quiet, comfortable, and dark sleeping environment and avoid excessive use of electronic devices before going to bed.

3. Establish regular sleeping habits: Maintaining a regular schedule helps regulate your biological clock and improve sleep quality.

4. Pay attention to physical health signals: If you experience health problems such as insomnia, difficulty sleeping, depression, etc., you should seek medical attention in time, find out the cause and take appropriate measures.

5. Scientific intervention and treatment: If there are sleep problems, scientific intervention and treatment can be carried out under the guidance of a professional doctor, such as cognitive behavioral therapy, drug therapy, etc.

References: LiY, Gong W, Sahakian BJ, et al. Divergent biological pathways linking short and long sleep durations to mental and physical health. Nature Mental Health (2025).