Being a night owl, like middle-aged and older adults – particularly women – means having worse cardiovascular health compared to a person who is more diurnal and active during the day, according to a study published in the Journal of the American Heart Association, the journal of the American Heart Association.
For the study, researchers reviewed health data from more than 300,000 adults (average age 57) from the UK Biobank (one of the most comprehensive biometric databases in the world) to analyze how chronotypes-an individual’s natural preference for sleep schedule-affect cardiovascular health.About 8% of participants said they were “definitely evening people,” a night owl profile, going to bed late (e.g., 2 a.m.) and being more active ultimately.
People who described themselves as “definitely morning people,” were more active earlier in the day and went to bed earlier (e.g., 9 pm), and represented almost a quarter of the participants.About 67% of the participants were classified as having “intermediate” chronotype as they could not tell whether they were daytime or night owls.
the study measured participants’ cardiovascular health using metrics such as diet, physical activity, tobacco use, sleep quality, and levels of weight, cholesterol, blood sugar, and blood pressure.
The analysis found that compared to intermediate chronotypes, “evening people” or nocturnal people had a 79% higher prevalence of having a poor overall cardiovascular health score.Additionally, night owls had a 16% higher risk of heart attack or stroke over a median of about 14 years of follow-up, compared wiht people in the intermediate category.
The study also linked evening or night-time chronotype with worse cardiovascular health scores in women than in men.
Much of the increased cardiovascular risk among night owls is due to these people having poor habits and heart health factors, especially nicotine use and inadequate sleep.
In contrast, “day people,” or early risers, showed a 5% lower prevalence of low heart health scores compared to others.
“‘Evening people’ often experience circadian misalignment, meaning their internal body clock may not match the natural day-night light cycle or their typical daily schedules,” explains the study’s lead author, Sina Kianersi, a research associate in the division of sleep and circadian disorders at Brigham and Women’s hospital and Harvard Medical school, both in Boston.
“evening people are more likely to engage in behaviors that may affect cardiovascular health, such as a poorer quality diet, smoking, and inadequate or irregular sleep.”
It’s not all bad news for the night owl
However, the study’s findings aren’t all bad news for the night owl, says kristen Knutson, president of the American Heart Association’s 2025 statement, who was not involved in the research.
“These findings show that the increased risks of heart disease among evening chronotypes are partly due to modifiable behaviors such as smoking and sleep. Therefore, these people have options to improve their cardiovascular health,” he comments.
In fact,the American Heart Association scientific statement that Knutson led suggests that individual chronotype should be taken into account when choosing interventions or treatments: “Some medications or therapies work best when aligned with a specific timing of the relevant circadian rhythms,and this timing will vary depending on whether you are a morning,intermediate,or evening chronotype.”
Among the main limitations of the study, the authors note that the majority of biobank participants were white and generally healthier than the general