Middle-aged and older adults who naturally stay up late show a 79% higher prevalence of poor cardiovascular health and a 16% higher risk of heart attack or stroke than people with intermediate sleep timing, according to a new analysis of UK Biobank data published in the Journal of the American Heart Association.
What the study measured
Researchers drew on health records from more than 300,000 adults, with an average age of about 57, who had taken part in the long-running UK Biobank study. Each participant self-identified as a “definitely morning” person, a “definitely evening” person, or “intermediate.” Roughly 8% described themselves as definite evening types, about 24% as definite morning people, and around 67% as intermediate.
Cardiovascular health was scored using the American Heart Association’s Life’s Essential 8 framework, which covers diet, physical activity, smoking status, sleep quality, body weight, cholesterol, blood sugar, and blood pressure.
Key findings on heart health and chronotype
Compared with intermediate chronotypes, evening types had a 79% higher prevalence of poor overall cardiovascular health scores. Over a median follow-up of about 14 years, night owls also showed a 16% higher risk of heart attack or stroke. The link between evening preference and poorer heart outcomes was stronger in women than in men.
Definite morning types showed the opposite pattern, with a 5% lower prevalence of poor cardiovascular health scores compared with intermediate participants.
Why evening chronotypes carry higher risk
Much of the extra risk tracked back to modifiable behaviors, especially higher rates of smoking, inadequate sleep, and poorer diet. Researchers described the pattern as “circadian misalignment,” meaning that an evening person’s internal clock often does not line up with the daylight cycle or typical daily schedules.
Higher risk comes from modifiable behaviors, not from being a night owl.
What the researchers recommend
The study’s lead author, a research fellow in sleep and circadian disorders at Brigham and Women’s Hospital and Harvard Medical School, noted that evening people tend to have behaviors that can affect cardiovascular health, such as poorer diet quality, smoking, and inadequate or irregular sleep.
A separate sleep and circadian scientist who chairs the 2025 American Heart Association statement on circadian health and cardiometabolic risk, and was not involved in the research, added that evening types face challenges that make a healthy lifestyle especially important for them. Some medications and therapies work best when aligned with a person’s natural rhythms, so timing can matter depending on whether someone is a morning, intermediate, or evening chronotype.
The practical message is that targeted programs for people who naturally stay up late, along with attention to diet, smoking cessation, and consistent sleep, could help reduce cardiovascular risk in this group.
The bottom line for night owls
Being an evening person is not, on its own, a health verdict. The UK Biobank data point to behavior, especially sleep regularity, smoking, and diet, as the main levers for protecting heart health. Aligning daily routines, meals, and any time-sensitive medications with a person’s natural chronotype offers a practical path to lowering cardiovascular risk.
FAQ
What did the night owl heart study find?
An analysis of more than 300,000 UK Biobank participants, published in the Journal of the American Heart Association, found that evening chronotypes had a 79% higher prevalence of poor cardiovascular health and a 16% higher risk of heart attack or stroke over about 14 years, compared with intermediate chronotypes.
How many people were in the study?
The study used data from more than 300,000 middle-aged and older adults, with an average age of about 57, participating in the UK Biobank.
Can night owls reduce their cardiovascular risk?
Researchers said most of the excess risk among evening types was tied to modifiable behaviors such as smoking, poor diet, and inadequate or irregular sleep. Improving these habits and timing medications or interventions to match a person’s natural chronotype can help lower cardiovascular risk.
