Sleep and Longevity: What the Research Really Shows

Sleep and longevity are a popular topic, but the research behind it is more sober than many guides suggest. Large population studies do not measure «longevity» or healthy life years as a separate quantity; they measure mortality risk as a function of sleep duration and regularity. The term «longevity» is used in this article as a thematic framing for search purposes, not as a measure used in the cited studies themselves. What shows up across several large cohort studies and in the American Heart Association's scoring scheme is this: both short and long sleep are statistically associated with a higher mortality risk than a medium sleep duration — the relationship is U-shaped, not linear. All the studies named below are also observational studies: they show statistical associations, not proven cause-and-effect chains. According to this data, no bed, mattress or light fitting can lower mortality risk — the studies make no claim about that at all.

The largest and most-cited basis is a 2010 meta-analysis by Cappuccio and colleagues: 16 prospective cohort studies with 27 independent cohorts, 1'382'999 participants and 112'566 deaths, with observation periods of 4 to 25 years, sleep data drawn mostly from self-reported questionnaires. The study found that short sleep duration was associated with a 12% higher relative mortality risk (RR 1.12). Long sleep duration was associated with an even greater increase in risk, 30% (RR 1.30) — the authors themselves read this as a U-shaped relationship between sleep duration and mortality, not a linear «more sleep is always better».

A dose-response meta-analysis by Yin and colleagues (2017), which reviewed the literature up to December 2016 — also based mostly on self-reported sleep duration — finds the same pattern for all-cause mortality as well as for cardiovascular disease, coronary heart disease and stroke: a U-shaped relationship with the lowest observed risk at around 7 hours of sleep per day. Below 7 hours, the pooled relative mortality risk rose by 6% per hour of shorter sleep. Above 7 hours, the increase in risk per additional hour was even more pronounced than for short sleep: 13% higher mortality risk per hour, and for stroke as much as 18% per additional hour of sleep beyond 7 hours. The roughly 7 hours found in this study is the low point of the observed risk curve — a statistical reference point, not a recommendation from the authors.

The authors of the underlying studies explicitly point out this limitation. Cappuccio and colleagues note that the link between long sleep and mortality risk could also be explained by unmeasured confounding factors — such as depression, low socioeconomic status, low physical activity, undiagnosed illness or cancer-related fatigue — and call for further research to clarify whether sleep duration is a cause or merely a marker of poor health status. Yin and colleagues likewise stress that only long-term randomised controlled trials could demonstrate a causal effect of sleep duration on mortality — their own meta-analysis provides only observational evidence for this. Even the American Heart Association states in its advisory that there is little evidence that improving sleep duration or sleep quality reduces the incidence of cardiovascular disease. In practice, this means: the figures in this article describe statistical associations across large population groups, not an individual prediction, and not a proven effect of «more» or «more regular» sleep on one's own mortality.

A more recent study by Windred and colleagues (2024) shifts the focus from pure sleep duration to sleep regularity. It is based on a UK Biobank cohort with objective accelerometer data from 60'977 people with an average age of 62.8 years, more than 10 million hours measured, and a mortality follow-up of up to 7.8 years. The result: sleep regularity, measured using a regularity index, was a stronger predictor of all-cause mortality in this cohort than sleep duration alone. Participants in the four most regular sleep quintiles had a 20 to 48% lower risk of all-cause mortality than the least regular group, even after adjusting for age, sex, ethnicity, and sociodemographic, lifestyle and health factors. The same caveat applies here too: the authors themselves point out that their findings are purely correlational, and that sleep regularity could be either a cause or merely a marker of premature mortality. The sample also comes from a predominantly older, ethnically homogeneous population, with only one week of measurement per person — so it cannot readily be generalised to younger or more ethnically diverse groups.

At the level of professional bodies, this body of research has made its way into official scoring frameworks: in 2022 the American Heart Association added sleep duration as the eighth component of its definition of cardiovascular health («Life's Essential 8»), captured as self-reported average hours of sleep per night. In the scoring scheme, 7 to under 9 hours of sleep per night receives the full score of 100 possible points; both shorter and longer sleep duration — including 10 hours or more — scores lower, deliberately reflecting the U-shaped relationship. The basics of sleep needs, the immune system and Swiss figures are covered in our guide «Why Good Sleep Matters» — this article focuses on the mortality data and its limitations.

What remains for everyday life is sober guidance, not a promise: in the large population studies and in the American Heart Association's scoring scheme, a sleep duration of 7 to 9 hours per night fares best — markedly shorter as well as markedly longer sleep shows a higher statistical mortality risk in the same data. In addition, in the study by Windred and colleagues, the regularity of sleep timing was more closely linked statistically to all-cause mortality than the number of hours alone — an association drawn from observational data, not a proven effect. None of the cited studies shows any link between the quality of a mattress, bed or light fitting and these mortality figures; anyone who nonetheless wants to reconsider their own sleep environment will find space to try lying down at our premises at Nüschelerstrasse 30 in Zurich — as an aid to deciding how a bed feels to you personally, not as evidence for a research finding.