Staying up late is tied to a 10% higher chance of dying young

Self-described night owls faced a 10% higher risk of dying during a roughly 6.5-year tracking period than early risers, according to a study of more than 433,000 UK adults published in the journal Chronobiology International. Death certificates were checked an average of 6.5 years after participants reported their own sleep chronotype at the start of the study. The gap held up even after researchers accounted for existing health conditions participants had when they enrolled.

A 10% mortality gap across 6.5 years

Researchers Kristen Knutson of Northwestern University and Malcolm von Schantz of the University of Surrey classified each participant as a definite morning type, moderate morning type, moderate evening type or definite evening type, based on a self-reported chronotype questionnaire. They then tracked which participants had died by the time official death records were checked, roughly 6.5 years later on average, and compared mortality rates across the four groups. Participants had been recruited between the ages of 38 and 73, old enough that the study captured a meaningful number of deaths from natural causes without needing an especially long follow-up window to do it.

“Night owls trying to live in a morning lark world may have health consequences for their bodies,” said Knutson, describing the mismatch between a late internal clock and a schedule built around early mornings, in comments distributed through Northwestern University. Von Schantz put it more bluntly: “This is a public health issue that can no longer be ignored,” he said.

The underlying idea, sometimes called social jetlag, is that a person’s internal circadian clock can run later than the schedule imposed by work, school or family life, forcing evening types to wake earlier than their biology prefers on most days. Researchers in sleep medicine have described that chronic mismatch, rather than late nights on their own, as the more plausible driver of the health differences the study found between morning and evening types.

433,000 UK Biobank records, sorted by chronotype

The data came from UK Biobank, a research resource that has enrolled roughly half a million volunteers recruited between 2006 and 2010 to track long-term health outcomes, according to UK Biobank’s own description of the project. Knutson and von Schantz’s analysis used 433,268 of those volunteers who had answered the chronotype questions and had complete follow-up data available, making it one of the largest sleep-and-mortality analyses of its kind at the time.

The study appeared in Chronobiology International in April 2018, and its size is part of why the 10% mortality figure still gets cited in health coverage years later — few sleep studies track outcomes across hundreds of thousands of people for years at a stretch.

Diabetes and psychiatric diagnoses cluster among night owls

Beyond the mortality gap, the research, corroborated by a summary distributed through EurekAlert, found evening types were diagnosed with diabetes, neurological disorders and psychological disorders more often than morning types over the same period. Those associations do not prove that staying up late causes any single disease, but they track with a pattern researchers have long noticed in shift workers and others whose sleep schedules run against a typical daytime routine.

Von Schantz pointed to a smaller, related signal as evidence the mismatch has measurable physical effects: reports of a higher rate of heart attacks in the days immediately after clocks shift forward each spring, when most people abruptly lose an hour of morning light at once.

Two researchers, one open question about causation

As Smithsonian magazine noted when covering the findings, the higher risk does not mean every night owl is destined for an early death: a self-reported chronotype is only loosely tied to actual behavior, and the study measured association rather than cause. Shift work, alcohol use and untreated sleep disorders are all more common among people who identify as evening types, and any one of them could explain part of the gap on its own. That is also why the researchers stopped short of recommending night owls simply force themselves into an earlier bedtime, since shifting sleep timing without addressing the underlying mismatch between someone’s biological clock and an imposed schedule has not been shown to erase the risk on its own.

Knutson has said the mismatch between an internal body clock and an externally imposed schedule, not the late bedtime by itself, is the more likely mechanism worth studying further, a distinction that matters for anyone whose work or family schedule already runs late rather than by choice.

Neither Knutson nor von Schantz has published a follow-up UK Biobank analysis updating the 10% figure since 2018, so the number still circulating in health coverage today is the same one their original 433,268-person sample produced nearly a decade ago.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.

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