Adults who identify as “night owls” may face significantly higher risks to their heart health, according to a major new study that links late sleep schedules to poorer cardiovascular outcomes. Researchers found that people who are more active in the evening had substantially worse heart health scores and a higher likelihood of heart attack or stroke compared to those with earlier or more balanced sleep patterns.
The study, published Wednesday in the Journal of the American Heart Association, analyzed nearly 14 years of health data from approximately 300,000 adults enrolled in the UK Biobank. Participants averaged 57 years old at the start of the study and were categorized based on their self-identified chronotype, or natural preference for morning or evening activity.
About 8 percent of participants described themselves as “definitely evening people,” meaning they regularly stayed up very late, while 24 percent identified as “definitely morning people.” The majority, roughly 67 percent, fell into an intermediate category, reporting no strong preference for either early or late schedules.
Researchers assessed cardiovascular health using the American Heart Association’s “Life’s Essential 8” score, which evaluates physical activity, diet, blood pressure, cholesterol levels, nicotine use, sleep duration, body weight, and blood sugar. Over the study period, individuals classified as evening types had a 79 percent higher risk of poor cardiovascular health compared to the intermediate group and a 16 percent higher risk of experiencing a heart attack or stroke.
Those who identified as morning-oriented tended to score slightly better on overall heart health measures. The association between late chronotype and cardiovascular risk was especially pronounced among women, according to the findings.
Lead author Sina Kianersi, a research fellow at Brigham and Women’s Hospital and Harvard Medical School, said evening-oriented individuals often experience “circadian misalignment,” meaning their internal body clocks do not align well with natural light cycles or typical work and social schedules. This misalignment, she noted, may contribute to unhealthy behaviors such as irregular sleep, poorer diet quality, and higher rates of smoking.
Dr. Bradley Serwer, an interventional cardiologist not involved in the study, emphasized that lifestyle habits likely play a major role in the observed risks. He said the findings could help physicians better tailor lifestyle recommendations and preventive strategies for patients who naturally prefer later schedules.
Researchers cautioned that the study does not prove that staying up late directly causes heart disease, only that an association exists. The analysis also relied on self-reported data, which may introduce bias, and the UK Biobank population is predominantly White and generally healthier than the broader population, limiting how widely the results can be applied.
Still, the findings add to growing evidence that sleep timing, not just sleep duration, may be an important factor in long-term cardiovascular health.
