July 30, 2025, 10:55 am | Read time: 6 minutes
How long we sleep is important—but when and how regularly we sleep seems even more crucial. A large-scale study involving nearly 90,000 adults shows: Irregular sleep is linked to numerous diseases—from diabetes to depression. Particularly interesting: Many risks were not identified in earlier studies because they relied solely on subjective sleep reports. The new findings demonstrate how significantly objectively measured sleep can impact our health.
Connection Between Objectively Measured Sleep Patterns and Health
Sleep is vital. It affects nearly all processes in the body, such as the immune system, metabolism, and brain regeneration. However, most previous studies are based on what people report about their own sleep—that is, on subjective assessments, such as from questionnaires. The problem: These reports are often inaccurate or distorted.
Researchers at Peking University wanted to find out how the connection between objectively measured sleep patterns and our health looks—specifically, how long, when, and how regularly people actually sleep, regardless of what they believe or report.
For the study, data from 88,461 adults from the UK Biobank were analyzed. All participants wore a small movement sensor (accelerometer) on their wrist for a week. This allowed researchers to track when they fell asleep, how long they slept, how often they woke up during the night, and how much their sleep varied from day to day.
The goal was to determine which diseases these sleep patterns are associated with—and whether previous studies that relied only on self-reports might have drawn incorrect conclusions.1
Study Design: Approach Taken
In the study, six objective sleep characteristics were evaluated:
- Sleep duration
- Time of falling asleep
- Relative amplitude (the difference between daytime and nighttime activity—the greater, the healthier the sleep-wake rhythm)
- Interdaily stability (how regularly one sleeps at the same time)
- Sleep efficiency (how much time in bed is actually spent sleeping)
- Nighttime awakenings (how often someone wakes up during the night)
The researchers tracked which new diseases were diagnosed in participants over 6.8 years. The basis for this was medical diagnostic codes (ICD-10 codes)—an internationally used classification system that clearly names and statistically records diseases.
A total of 363 different diseases from 13 medical fields were examined, including cardiovascular diseases, mental disorders, metabolic diseases, and many more.
To determine how sleep and disease are related, the researchers used a statistical method called the Cox model. It calculates the relative risk of developing a specific disease—depending on the expression of a particular factor, in this case, sleep behavior. Many other influences were considered, such as age, gender, weight, diet, exercise, or smoking.
Result: Sleep Rhythm Is Linked to Many Diseases
The analysis shows: 172 diseases were linked to sleep behavior—almost half of all diagnoses examined. Particularly with severely disrupted sleep patterns, the risk was significantly increased.
Examples:
- People with very irregular sleep rhythms had nearly three times the risk of Parkinson’s.
- Those who regularly fell asleep after 12:30 a.m. had more than double the risk of liver cirrhosis.
- An unstable sleep rhythm significantly increased the risk of vascular diseases like gangrene.
- For type 2 diabetes, the risk increased by 60 percent when sleep times were particularly irregular.
Particularly striking: Almost half of all discovered connections (48.3 percent) involved the sleep rhythm, meaning the regularity and structure of sleep—not just the sleep duration. Previous studies often ignored this aspect.
Subjective Sleep Reports Often Led to Misconceptions
The researchers also reviewed several connections that had been established in previous studies based on subjective reports—such as the claim that “long sleep duration” (over nine hours) supposedly increased the risk of heart disease or depression.
The researchers of the current study could not confirm these connections when they objectively measured actual sleep times. About 22 percent of people who claimed to sleep long actually slept less than six hours. Their self-assessment was significantly off. And this misjudgment can lead to false positive results—that is, to supposed risks that do not actually exist.
Confirmation of Results with NHANES Data
To ensure that the newly discovered connections were not coincidental, the researchers conducted an additional analysis within the same study—this time with data from the U.S. NHANES health study, a large population survey with over 8,500 adults. These data came from national surveys conducted from 2011 to 2014, where participants—like in the UK Biobank—provided objectively measured sleep and movement data via accelerometers.
The investigation revealed four clear connections: COPD (chronic obstructive pulmonary disease), acute kidney failure, diabetes, and depression, each of which appeared in a clearly traceable connection to one another. Furthermore, it was shown that even in this independent sample, a disrupted sleep rhythm was clearly associated with an increased risk of disease.
Also interesting: Is the Clock the Enemy of Our Sleep?
Why These Findings Are So Important
The study shows: Our sleep behavior—especially the rhythm—has a significant impact on the development of many diseases. And: Many previous studies may have misjudged risks or overlooked important connections because they relied only on surveys.
Almost 58 percent of the found disease relationships involved only a single sleep characteristic—such as just the time of falling asleep or the regularity. This is precisely why it is not enough to focus only on sleep duration. To truly stay healthy, one must also pay attention to a stable sleep rhythm.
The good news: The sleep rhythm is changeable. Regular sleep times, less screen use before sleeping, and a structured daily routine can help. Additionally, the study showed that disrupted sleep is associated with increased inflammation levels in the blood (such as C-reactive protein)—a possible biological mechanism explaining why poor sleep can make one sick.
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Assessment: Strengths and Weaknesses of the Study
The investigation is one of the most comprehensive worldwide on the topic of sleep and diseases.
Strengths:
- A very large number of participants
- Long follow-up period
- Objective sleep measurement with modern sensors
Limitations:
- Participants in the UK Biobank are not fully representative of the general population (mostly healthier, older, better educated).
- The research team only captured sleep at one point in time and ignored developments over time.
- Observational data do not allow definitive statements about cause and effect.
Conclusion
The investigation suggests that objective sleep measurements could play a more important role in researching disease causes in the future. The study indicates that certain health connections may have been underestimated so far—especially if they were based on subjective self-reports. Further studies will need to show to what extent such measurement methods can also contribute to disease prevention in practice.