Early Birds vs. Night Owls: Which Sleep Pattern Is Riskier for the Heart

People who naturally tend to go to bed late and wake up late — so-called “night owls” — are more likely to have heart health problems compared to those with a more traditional sleep schedule. This link appears to be especially strong among women.

The findings of a new study were published in the Journal of the American Heart Association.

Researchers analyzed the health status and behavioral habits of nearly 323,000 adult participants from the UK Biobank project, one of the largest medical databases in the United Kingdom. The average age of participants was 57. All of them completed a questionnaire indicating their chronotype — the time of day when they feel most alert and active.

“Growing evidence suggests that misalignment between our internal biological clocks and daily life rhythms may negatively affect cardiometabolic health,” said lead author Sina Kianersi, a researcher in the Division of Sleep and Circadian Disorders at Brigham and Women’s Hospital at Harvard Medical School.

About 24% of participants identified as “early birds,” 8% as “night owls,” and the vast majority — 67% — fell somewhere in between.

To assess heart health, the team used the American Heart Association’s Life’s Essential 8 framework, assigning each participant a score from 0 to 100. The evaluation included sleep quality, body weight, diet, blood sugar levels, blood pressure, cholesterol, smoking status, and physical activity. The average heart health score was 67.4, with women scoring higher than men.

Compared with the intermediate group, night owls had a 79% higher likelihood of poor heart health — defined as a score below 50 — while early birds had a 5% lower risk. Over an average follow-up period of 14 years, night owls were also 16% more likely to experience heart attacks and strokes.

The authors emphasize that the increased risk is not due solely to chronotype itself, but rather to the combination of lifestyle and health factors associated with it — the overall cardiovascular health profile largely explains the elevated risk.

Sleep plays a crucial role in heart health. The American Heart Association recommends that adults get seven to nine hours of sleep per night. During sleep, the body repairs tissues, regulates hormones, and “resets” at the cellular level. Chronic sleep deprivation, irregular schedules, or poor sleep quality can gradually increase stress hormone levels and contribute to cardiovascular disease.

At the same time, experts stress that being a night owl is not a sentence. The link between an evening chronotype and heart risk is moderate. Many unhealthy habits more common among night owls are modifiable — quitting smoking, increasing physical activity, limiting late-night eating, managing light exposure, and avoiding caffeine several hours before bedtime can significantly improve outcomes.

The study has limitations: participants were mostly white and middle-aged or older, and chronotype was based on self-reporting. Still, the authors believe the findings help better understand biological differences between people and reduce the stigma around night owls.

“They are often labeled as lazy,” researchers note, “but it’s not about laziness — their internal rhythm simply works differently.”

Follow NEWS.am Medicine on Facebook and Twitter