Late bedtimes are linked to higher heart disease risk, reports research

Late-Night Activity Tied to Poorer Heart Health

Adults in middle age and later life who tend to be more active in the evening were found to have worse cardiovascular health than those who are active earlier in the day. The association appeared to be stronger 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.

The findings suggest that when people are most active during the day may play an important role in long-term heart health.

Study Tracks Sleep Timing in More Than 300,000 Adults

Researchers examined health data from more than 300,000 adults (average age of about 57 years) enrolled in the UK Biobank. The analysis focused on chronotypes, which describe a person's natural preference for sleep and wake timing, and how those preferences relate to cardiovascular health.

Participants were grouped based on their self-identified daily patterns. About 8% described themselves as "definitely evening people," meaning they typically went to bed very late (for example 2 a.m.) and reached peak activity later in the day. Around 24% reported being "definitely morning people," who tended to wake up earlier, go to bed earlier (for example 9 p.m.), and be most active earlier in the day. The remaining 67% were categorized as having an "intermediate" chronotype if they were unsure or said they were neither clearly a morning nor evening person.

Cardiovascular health was evaluated using the American Heart Association's Life's Essential 8™ metrics. This framework looks at behaviors and health factors known to support heart health, including eating a healthy diet, staying physically active, not smoking, and getting good-quality sleep. It also includes maintaining healthy levels of body weight, cholesterol, blood sugar, and blood pressure.

Key Differences Between Night Owls and Early Birds

The researchers identified several notable patterns when comparing chronotype groups:

Compared with people in the intermediate category, those classified as "evening people," often called night owls, were 79% more likely to have an overall poor cardiovascular health score.

Night owls also had a 16% higher risk of experiencing a heart attack or stroke during a median follow-up period of about 14 years.

The link between evening chronotype and lower heart health scores was stronger among women than among men.

Much of the increased heart disease risk seen in evening types was linked to lifestyle habits, particularly nicotine use and insufficient sleep.

In contrast, "morning people," also known as early birds, showed a 5% lower prevalence of poor cardiovascular health scores compared with individuals without a strong morning or evening preference.

Why Evening Types May Face Added 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," 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."

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

Lifestyle Changes Could Reduce Risk

The findings are not entirely discouraging for people who prefer late nights, 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 the study.

"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."

Tailoring Treatment to Body Clocks

The American Heart Association scientific statement led by Knutson also recommends taking chronotype into account when planning treatment or lifestyle interventions.

"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."

Study Limitations

The researchers noted that most UK Biobank participants were white people and generally healthier than the overall population, which may limit how broadly the findings apply to other groups. In addition, chronotype was assessed only once and was based on self-reported information rather than repeated measurements.

Reference:

Sina Kianersi, Kaitlin S. Potts, Heming Wang, Tamar Sofer, Raymond Noordam, Martin K Rutter, Kathryn Rexrode, Susan Redline, Tianyi Huang. Chronotype, Life’s Essential 8, and Risk of Cardiovascular Disease: A Prospective Cohort Study in UK Biobank. Journal of the American Heart Association, 2026; DOI: 10.1161/JAHA.125.044189