Night Owls May Have a Higher Risk of Heart Disease, New Study Finds

If you naturally stay up late and consider yourself a night owl, you may be putting yourself at risk.

According to a study published in the Journal of the American Heart Association, middle-aged and older adults, especially women, who are more active in the evenings showed worse heart health than early birds.

The study analyzed data from more than 322,000 adults who participated in the UK Biobank, a longitudinal study that included participants from England, Scotland, and Wales. The participants ranged in age from 39 to 74 years old and did not have cardiovascular disease.

The participants self-identified their chronotype—their natural preference for when they go to bed and when they wake up—and were categorized as morning, intermediate, or evening types. The evening chronotype was characterized by a late bedtime and peak activity later in the day, while a morning chronotype had an earlier bedtime and was most active in the morning. The rest fell somewhere in between.

Adults with an evening chronotype were associated with a higher risk of circadian misalignment due to the mismatch between their internal circadian rhythms and the external natural and social environment, such as work schedules. According to the study, circadian misalignment can potentially promote unhealthy lifestyle behaviors such as irregular sleep patterns, poor diet, heavy alcohol drinking, and smoking.

To measure the participants' health, the researchers used the American Heart Association’s Life’s Essential 8. The eight factors are healthy eating, being active, not smoking, getting high sleep quality, and managing weight, cholesterol, blood sugar, and blood pressure. Each component is scored from 0 to 100, with higher scores indicating better cardiovascular health.

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Participants with a "definite evening" chronotype were 79 percent more likely to have overall poor cardiovascular health as compared to the "intermediate" types. Meanwhile, early birds had a five percent lower prevalence. Night owls also had a higher risk of heart attack or stroke after an almost 14-year follow-up, the study reports.

It should be noted that because this was an observational study, the findings cannot prove that chronotype directly causes poorer cardiovascular health or increased cardiovascular risk.

"'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," lead study author Sina Kianersi, Ph.D., D.V.M., a research fellow in the division of sleep and circadian disorders at Brigham and Women's Hospital and Harvard Medical School, said in a release.

"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," she added. This misalignment may make it harder for night owls to maintain habits that support long-term heart health.

Kristen Knutson, Ph.D., FAHA, volunteer chair of the 2025 American Heart Association, said in the same release that "these findings show that the higher heart disease risks among evening types are partly due to modifiable behaviors such as smoking and sleep. Therefore, evening types have options to improve their cardiovascular health. Evening types aren't inherently less healthy, but they face challenges that make it particularly important for them to maintain a healthy lifestyle." Knutson was not involved in the study.