Recent research published in the Journal of the American Heart Association1 finds that people who tend to be active late into the evening, commonly referred to as “night owls” may face worse cardiovascular health and a higher risk of heart attack or stroke compared with individuals who sleep earlier. These associations appear particularly pronounced among women.
The analysis included data from 322777 adults participating in the UK Biobank, a large long-term health database encompassing adults aged around 57 years on average. Participants were grouped based on their chronotype, a self-reported measure of whether they are morning types, intermediate, or “definitely evening” types (night owls) who naturally stay up late and reach peak activity later in the day.
Researchers evaluated cardiovascular health using the American Heart Association’s Life’s Essential 8 metrics, a composite score derived from eight key factors:
Healthy diet
Physical activity
Smoking status
Sleep quality
Body weight
Blood pressure
Cholesterol levels
Blood sugar levels
A higher score indicates better overall cardiovascular health.
People classified as “definitely evening types” had a 79% higher prevalence of poor cardiovascular health compared with intermediate chronotypes.
Over a median follow-up period of about 14 years, night owls also had a **16% higher risk of experiencing a first heart attack or stroke compared with individuals without a strong morning or evening preference.
Several reports from this study note that the connection between evening chronotype and poorer heart health was more pronounced among women, though researchers highlight that lifestyle factors contributed significantly to the overall risk patterns observed.
Chronotypes reflect differences in individuals’ internal body clocks, which normally align with the 24-hour day-night cycle. When internal rhythms mismatch actual sleep and activity schedules — a situation known as circadian misalignment — key body functions including blood pressure, hormone release, metabolism, and heart rate regulation may be disrupted.
Night owls in the study also tended to exhibit behaviors linked to cardiovascular risk, including:
Poorer diet
Smoking or exposure to smokers
Inadequate or irregular sleep
These factors can influence heart health independently and collectively over time.
Because this is an observational study, it cannot definitively prove that being a night owl causes heart disease. Instead, it shows a statistically significant association between late sleep timing and poorer heart health outcomes. Other sleep research similarly reports that irregular sleep patterns and poor sleep quality are linked to increased cardiovascular risk.
Experts interpreting the results note that many contributors to heart risk — such as smoking, diet, and sleep habits — are modifiable. This suggests potential avenues for improving cardiovascular health even for individuals with evening chronotypes.
Prior research indicates that insufficient or irregular sleep is associated with heart disease risk factors including hypertension, metabolic dysfunction, and obesity, reinforcing the importance of sleep as part of overall heart health.
Several studies point out that women may experience unique cardiovascular risk patterns related to sleep disruption, though mechanisms remain under investigation and more research is needed to clarify these patterns across populations and age groups.
This large longitudinal study highlights a notable association between late bedtime preferences and increased cardiovascular risk, including heart attack and stroke outcomes, especially among women. While chronotype itself may not be inherently harmful, it correlates with behaviors and rhythms that can influence heart health over time. Awareness of sleep timing and related lifestyle habits may aid in heart disease prevention strategies.