New research connects being a “night owl” with weaker heart health and a slightly higher chance of heart attack or stroke, based on a long-term look at chronotypes and cardiovascular markers. The study tracked people’s natural sleep-wake preferences and measured heart health using an established scoring system. Findings point to behavior and biological timing as important pieces of the puzzle.
The paper analyzed roughly 14 years of health data from a large UK cohort to explore how morning versus evening tendencies relate to heart risk. Researchers grouped adults by their self-identified chronotype and then compared cardiovascular metrics across those groups. The approach leaned on repeated measures and clinical markers rather than a single snapshot.
About 300,000 adults were included, with an average age in the late 50s, giving the analysis plenty of statistical power. Participants reported their own sleep habits, which the team used to classify people as morning, evening, or intermediate types. The investigators treated these self-reports carefully but noted their limits.
In the sample, roughly 8 percent called themselves “definitely evening people,” while about 24 percent said they were “definitely morning people.” The remaining two-thirds fell in the middle, identifying as neither extreme. Those splits let the researchers compare extremes against a large middle group.
Heart health in the study was scored using the American Heart Association’s metric known as Life’s Essential 8. “Life’s Essential 8 is a comprehensive assessment that includes activity levels, diet, blood pressure, cholesterol, use of nicotine, sleep patterns, weight management and blood sugar,” the study cited to explain the measure. That composite aims to capture both behaviors and physiological risk factors.
The core result was stark: people identifying as evening types had much worse cardiovascular scores and a modestly higher event risk. Night owls showed a 79% greater chance of landing in the poor cardiovascular health category versus the intermediate group, and a 16% higher risk of a heart attack or stroke during follow-up. Morning types tended to score a bit better, and the association appeared stronger among women.
“‘Evening people’ often experience circadian misalignment, meaning their internal body clock may not match the natural day-to-night light cycle or their typical daily schedules,” said lead study author Sina Kianersi, Ph.D., noting biological timing can clash with social demands. “Evening people may be more likely to have behaviors that can affect cardiovascular health, such as poorer diet quality, smoking, and inadequate or irregular sleep.” Those lifestyle differences likely contribute to the patterns seen.
Independent clinicians emphasized that habits matter alongside biology. “Cardiovascular disease has multiple contributing causes,” said one cardiologist who commented on the research, pointing out that sleep quality is one variable among many. “While quality sleep is important, further studies are required to show exactly what sort of impact sleep alone has on cardiovascular health.”
The authors and outside experts both stressed limits: the study found association, not proof of cause. It relied on participants’ self-reported schedules and behaviors, which can introduce bias or error. The cohort was also disproportionately White and generally healthier than average, which restricts how broadly the results can be applied.
Despite those caveats, the work suggests clinicians might consider chronotype when advising patients about lifestyle changes and risk reduction. Targeted counseling on diet, smoking cessation, and sleep regularity could help people whose internal clocks run late. Longer and more diverse studies will be needed to sharpen recommendations and guide practical interventions.
