For years, sleep experts have cautioned against getting too much sleep, linking it to heart disease, depression, and even premature death. However, new findings from the largest study of its kind suggest the real issue may not be the amount of sleep but how inaccurately we report it.
Why most people are wrong about how much they sleep
Researchers equipped nearly 90,000 adults with fitness trackers to objectively measure sleep patterns and followed their health outcomes over seven years. The study published in the journal Health Data Science on June 3, 2025, found that many participants who claimed to sleep more than eight hours were actually getting six hours or less. These “false long sleepers” were likely skewing previous studies that relied on self-reported sleep, inflating the perceived health risks of long sleep.
The research reveals a major flaw in decades of sleep research, people often misjudge how much they sleep. When scientists looked specifically at people who both reported and objectively had long sleep durations, the associated health risks nearly vanished.
Disrupted sleep rhythms linked to hundreds of diseases
Led by Dr. Qing Chen from China’s Third Military Medical University, the research used accelerometers from the UK Biobank to go beyond self-reporting. These wrist-worn trackers offered detailed insights not only into how long participants slept but also when they slept, how fragmented their sleep was, and how consistent their sleep patterns remained across days.
This granular data revealed that disrupted sleep rhythms, irregular schedules, poor consistency, and fragmented rest were linked to 172 diseases, including major chronic conditions. For example, individuals with highly disrupted sleep rhythms had three times the risk of age-related frailty and double the risk of developing gangrene.
Even more strikingly, disrupted sleep rhythms were tied to:
- 37% of Parkinson’s risk
- 36% of Type 2 diabetes risk
- 22% of acute kidney failure risk
Researchers calculated that for 92 diseases, over 20% of cases could theoretically be prevented with optimal sleep.
Sleep consistency matters more than duration
While most health advice focuses on getting 7–9 hours of sleep, this study found that when and how consistently you sleep might be even more critical.
Disrupted sleep rhythms were linked to 83 diseases not previously connected to sleep duration, conditions like COPD, kidney failure, and Type 2 diabetes. Validation through U.S.-based NHANES data confirmed these surprising associations, especially the strong link between irregular sleep and COPD.
Researchers also identified biological markers, like elevated white blood cells and C-reactive protein, that may explain how disrupted sleep leads to disease through chronic inflammation. Despite its strengths, the study had limitations: it focused on a largely White, healthy group and measured only one week of sleep data.
