A growing body of research links being a “night owl” – someone who naturally stays up late and wakes up late – to an increased risk of heart disease. A recent large-scale study from the UK Biobank, following over 322,000 adults for nearly 14 years, confirms this trend: individuals with a strong preference for evening sleep schedules face a significantly higher chance of cardiovascular problems.
The Study’s Findings: A Clear Correlation
Researchers categorized participants by chronotype (morning, intermediate, or evening) and assessed their heart health using the American Heart Association’s “Life’s Essential 8” score, a measure of cardiovascular well-being. The results were stark. “Definite evening” types were 79% more likely to have poor overall heart health scores and had a 16% higher risk of heart attack or stroke compared to intermediate sleepers. Conversely, those who naturally wake up early (“definite morning” types) had slightly better cardiovascular health.
Lifestyle vs. Biology: What Drives the Risk?
The question isn’t if there’s a link, but why. The UK Biobank data suggests that lifestyle factors play a major role. Night owls in the study exhibited 54% higher nicotine exposure, 42% poorer sleep quality, 19% lower physical activity, and 8% poorer diet compared to intermediate sleepers. When these behaviors are accounted for, approximately 75% of the increased risk among night owls appears to be attributable to modifiable habits, rather than their chronotype itself.
Smoking contributes the most (34%), followed by poor sleep (14%), high blood sugar (12%), and diet and body weight (11% each). This emphasizes that, while being a night owl may not directly cause heart disease, it’s often associated with behaviors that do.
The Role of Circadian Rhythms and Genetics
The link between chronotype and health isn’t purely behavioral. Night owls have genetically determined delayed circadian rhythms, meaning their internal biological clock is shifted later. This can lead to:
- Delayed melatonin release: Causing later sleep onset.
- Delayed cortisol release: Affecting wakefulness and stress response.
- Increased inflammation and oxidative stress: Contributing to blood vessel damage.
- Disrupted metabolic processes: Leading to elevated blood sugar, cholesterol, and insulin resistance.
Hundreds of genetic variants have been linked to chronotype, many of which regulate the body’s 24-hour clock. This isn’t just a matter of preference; it’s encoded in people’s biology.
Gender Differences and Future Research
Interestingly, the study revealed that the link between night owls and poorer heart health may be stronger in women than in men. Female night owls were 96% more likely to have poor cardiovascular health scores compared to intermediate sleepers, while male night owls were 67% more likely. Researchers suggest this discrepancy warrants further investigation, potentially involving social pressures, hormonal differences, or biological factors.
The study emphasizes the need for more research that establishes cause-and-effect relationships, potentially through genetic studies and intervention trials.
Conclusion
The findings underscore that while being a night owl isn’t a death sentence for your heart, it’s a clear signal to prioritize healthy habits. Improving sleep routines, exercising regularly, eating a balanced diet, and avoiding smoking are crucial steps toward mitigating cardiovascular risk. For those genetically predisposed to late sleep, proactive lifestyle management is particularly essential.
