A new large-scale study suggests that when people prefer to sleep and wake up may play a significant role in their long-term heart health.
Researchers report that adults who identify as “night owls” – those who naturally stay up late and wake later in the day – tend to have poorer cardiovascular health and a higher risk of heart attack and stroke compared to people with earlier or more balanced sleep schedules.
The findings, published in the Journal of the American Heart Association, are based on an analysis of health and lifestyle data collected over 14 years from the UK Biobank, a major research database that includes information on hundreds of thousands of participants.
The study examined roughly 300,000 to 320,000 adults aged between 39 and 74, with an average age of about 57.
Participants were asked to categorize themselves as “definite morning types,” “definite evening types,” or “intermediate,” meaning they did not strongly identify with either group.
About 8% of participants described themselves as clear evening types, while nearly a quarter said they were morning types. The majority, around two-thirds, fell into the intermediate category.
To measure heart health, researchers used the American Heart Association’s Life’s Essential 8 (LE8) score.
This comprehensive assessment evaluates four health behaviors – diet quality, physical activity, sleep duration, and nicotine exposure – along with four biological health factors, including blood pressure, cholesterol or blood fat levels, blood sugar, and body mass index.
The results showed a notable gap between sleep preference groups. Evening-type participants were 79% more likely to have poor overall cardiovascular health compared with those in the intermediate group.
They also faced a 16% higher risk of experiencing a heart attack or stroke during the follow-up period.
In contrast, morning-type participants had slightly better heart health scores and a modestly lower risk of poor cardiovascular outcomes.
Researchers emphasized that the increased risk among night owls does not appear to stem from sleep timing alone.
Instead, much of the elevated risk was linked to lifestyle habits that tend to accompany late schedules.
Nicotine use accounted for the largest share of the additional risk, explaining about one-third of the association.
Shorter sleep duration, elevated blood sugar levels, higher body weight, and poorer diet quality also contributed substantially.
Lead author Sina Kianersi, a research fellow specializing in sleep and circadian disorders, explained that many evening-type individuals experience “circadian misalignment.”
This occurs when a person’s internal biological clock does not match the demands of daily life, such as early work or school start times.
The resulting mismatch can disrupt sleep patterns and increase the likelihood of unhealthy behaviors, including irregular eating habits, reduced physical activity, and smoking.
Independent cardiology experts say the findings highlight how sleep interacts with broader lifestyle factors.
Dr. Bradley Serwer, an interventional cardiologist not involved in the study, noted that cardiovascular disease has many contributing causes and that sleep is only one piece of the puzzle.
However, he stressed that high-quality, restorative sleep should not be overlooked as part of overall heart health.
The study also revealed notable gender differences. While both men and women who identified as evening types showed poorer heart health scores, the association was stronger in women.
Researchers suggested that added social and caregiving responsibilities may intensify the strain of late-night schedules for many women, potentially worsening health outcomes.
Despite its scale, the study has limitations. Because the data relied on self-reported sleep habits and lifestyle behaviors, there is potential for reporting bias.
Additionally, the research establishesan association rather than direct causation, meaning it cannot definitively prove that staying up late causes heart disease.
The participant pool was also predominantly White and generally healthier than the broader population, which may limit how widely the results apply.
Still, experts believe the findings offer practical guidance. Improving sleep regularity, reducing smoking, maintaining a balanced diet, and incorporating physical activity – even in small amounts – could help offset some of the risks associated with late-night lifestyles.
As heart disease remains the leading cause of death in many countries, researchers say targeted prevention strategies that account for individual sleep patterns may become an important tool in reducing future cardiovascular events.
