Research Highlights:
- Middle-aged and older adults — particularly women — who are naturally more active in the evenings may have worse cardiovascular health, as measured by the American Heart Association's Life's Essential 8 metric, in comparison to peers without a strong morning or evening preference.
- Unhealthy behaviors among the night owls, such as poor diet quality, insufficient sleep and smoking, may account for their lower cardiovascular health profile, according to the analysis of data from the UK Biobank.
- Helping night owls improve their lifestyle habits may lower their risk for heart attack and stroke, researchers said.
DALLAS, Jan. 28, 2026 — Middle-aged and older adults who were more active in the evenings had poorer cardiovascular health compared to their peers who were more active during the day. This may be especially true among women, according to new research published today in the Journal of the American Heart Association, an open-access, peer-reviewed journal of the American Heart Association.
Researchers reviewed health data for more than 300,000 adults (average age of about 57 years) participating in the UK Biobank to assess how chronotypes—an individual's natural preference for sleep-wake timing—impacted their cardiovascular health.
About 8% of participants said they were "definitely evening people," which was characterized by having a late-night bedtime (for example 2 a.m.) and peak activity later in the day. Self-reported "definitely morning people," who were more active earlier in the day and had earlier bedtimes (for example 9 p.m.), made up about 24% of participants. About 67% of participants were classified as "intermediate" chronotype if they said they were unsure, or if said they were neither a morning person nor an evening person.
Cardiovascular health was measured according to the American Heart Association's Life's Essential 8™ metrics, which note health behaviors and health factors associated with optimal cardiovascular health. The metrics include a healthy diet, regular physical activity, not smoking, good sleep quality, as well as healthy levels for weight, cholesterol, blood sugar and blood pressure.
The analysis found:
- Compared to intermediate chronotypes, "evening people" or night owls had a 79% higher prevalence of having an overall poor cardiovascular health score.
- Night owls had a 16% higher risk of having a heart attack or stroke over a median of about 14 years follow-up, compared to people within the intermediate category.
- Evening chronotype was more strongly related to low cardiovascular health scores in women than in men.
- Much of the increased risk of heart disease among evening people was due to poor heart health habits and factors, especially nicotine use and inadequate sleep.
- In contrast, "morning people," or early birds, had a 5% lower prevalence of low heart health scores compared with those without a strong morning or evening chronotype.
"'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., D.V.M.; a research fellow in the division of sleep and circadian disorders at Brigham and Women's Hospital and Harvard Medical School, both in Boston. "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."
The study finding are not all bad news for night owls, according to Kristen Knutson, Ph.D., FAHA, volunteer chair of the 2025 American Heart Association statement, Role of Circadian Health in Cardiometabolic Health and Disease Risk. Knutson was not involved in this research.
"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," she said. "Evening types aren't inherently less healthy, but they face challenges that make it particularly important for them to maintain a healthy lifestyle."
The American Heart Association scientific statement Knutson led suggests that individual chronotype should be considered in guiding the timing of interventions or treatment.
"Some medications or therapies work best when they align with a specific time of relevant circadian rhythms, and this time will vary depending on whether you are a morning, intermediate, or evening chronotype," she said. "Targeted programs for people who naturally stay up late could help them improve their lifestyle behaviors and reduce their risk of cardiovascular disease."
Main limitations of the study include that most UK Biobank participants were white people and generally healthier than the broader population, which may limit how well the findings apply to other groups. In addition, evening vs. morning preference was measured only once and was self-reported.
Co-authors, disclosures and funding sources are listed in the manuscript. The study was partially funded by the American Heart Association.
