At a Glance
- night owls are linked to higher prevalence of poor heart health and increased risk of heart attacks or strokes.
- Women show a stronger association between evening chronotype and heart health.
- Early birds have a slightly lower prevalence of poor heart health compared to the intermediate group.
Why it matters: Understanding how sleep timing affects cardiovascular risk can guide lifestyle changes and medical advice.
Study Design and Key Findings
The research, published Wednesday in the Journal of the American Heart Association, examined data from nearly 323,000 adults in the UK Biobank, a longitudinal study that recruited participants between 2006 and 2010. Participants, with an average age of 57, completed a questionnaire that asked them to identify as a morning person, evening person, or intermediate. About 24% said they were morning people, 8% were evening people, and the remaining 67% fell into the intermediate group.
Lead author Sina Kianersi, a research fellow at Brigham and Women’s Hospital and Harvard Medical School, explained that the study used the American Heart Association’s Life’s Essential 8 metrics to generate a heart-health score ranging from 0 to 100. The metrics include sleep quality, weight, nutrition, blood sugar, blood pressure, cholesterol, smoking status, and physical activity. The overall average score was 67.4. Women scored an average of 70, while men averaged 65.
When the researchers compared the groups, night owls had a 79% higher prevalence of poor heart health-defined as a score below 50-than the intermediate group. Early birds, in contrast, had a 5% lower prevalence. Over a median follow-up of 14 years, night owls faced a 16% higher risk of heart attacks or strokes, whereas early birds did not show an increased risk.
Night owls also had higher likelihood of poor scores in six of the eight Life’s Essential 8 categories, including sleep and nicotine exposure. The strongest associations were seen in sleep quality and smoking status.
Expert Perspectives
Sina Kianersi emphasized that the link is not solely due to chronotype itself but also the associated health profile. “It’s not just that chronotype alone has something that raises night owls’ risk for cardiovascular disease,” he said, “but it is through that profile, or that poor cardiovascular health, that it causes that increased risk.”
Dr. Maha Alattar, medical director of the VCU Health Center for Sleep Medicine, highlighted the physiological role of sleep. “When we go to sleep, we go into physiological processes that actually help us regenerate some of our tissues, brain neurotransmitters – we kind of reset ourselves,” she said. She added that chronic sleep deficits can raise stress hormones like cortisol, which contribute to heart disease.
Dr. Shady Abohashem, head of cardiac PET/CT imaging trials at Massachusetts General Hospital, noted that while the association is modest, it is not fatal. “Being a night owl is not going to doom your heart,” he said.
Dr. Phyllis Zee, director of the Center for Circadian and Sleep Medicine at Northwestern University, offered practical advice. “Get your seven to eight hours’ sleep, stop smoking, increase your physical activity levels during the day,” she said. “All of these things will help you maintain better-quality sleep.” She also recommended stopping eating by 8 o’clock and ensuring exposure to natural light in the morning and dim light in the evening.
Practical Tips for Night Owls
| Habit | Why It Helps |
|---|---|
| Aim for 7-8 hours of quality sleep | Meets AHA recommendation and supports heart-health metrics. |
| Limit caffeine 12 hours before bedtime | Reduces stimulatory effect on the circadian rhythm. |
| Avoid smoking | Smoking is a major risk factor for cardiovascular disease. |
| Increase daytime physical activity | Improves weight, blood pressure, and cholesterol. |
| Stop eating 3 hours before bed | Improves digestion and sleep quality. |
| Expose yourself to bright light in the morning | Helps reset the internal clock. |
| Dim lights 2-3 hours before bedtime | Encourages melatonin production. |
Limitations of the Study
The researchers acknowledged several constraints. The cohort was predominantly white, middle-aged, and older adults who self-reported their chronotype, which may limit generalizability. Heart-health metrics were measured at a single point in time, so changes over the follow-up period were not captured. The study also relied on self-reported data for sleep and lifestyle behaviors.
Future Directions
Kianersi is currently investigating the genetics behind chronotypes to understand why the link between evening chronotype and heart health appears stronger among women. Alattar believes that better understanding of delayed sleep-wake syndrome can reduce stigma and help individuals manage their rhythms more effectively.
Key Takeaways
- Night owls have a higher prevalence of poor heart health and a higher risk of cardiovascular events.
- Women exhibit a stronger association between evening chronotype and heart health.
- Early birds show a modest protective effect.
- Lifestyle changes-adequate sleep, reduced caffeine, smoking cessation, increased activity, and proper light exposure-can mitigate risk.
- Further research is needed to clarify the genetic and biological mechanisms.
