The relationship between sleep and cardiovascular health

A new study published in the Journal of the American Heart Association analyzed data from more than 322,000 adults in the United Kingdom, Scotland and Wales. Participants self-identified their chronotype—an individual’s natural circadian preference for sleep and wake times—and were grouped into morning-active, intermediate, and evening-active categories based on self-assessment.

“Chronotype reflects each person’s natural tendency regarding sleep timing and daily activity,” said Sina Kianersi, the study’s lead author and a postdoctoral researcher at Brigham and Women’s Hospital and Harvard Medical School. This includes people who are “early birds,” “night owls,” or those in between.

Evening chronotypes linked with worse cardiovascular health

Kianersi said the evening-active group—and even some early birds—may face a higher risk of cardiovascular disease when their internal clock is not aligned with work schedules and other external factors.

Using the American Heart Association’s Life’s Essential 8 framework, the study assessed eight cardiovascular health components: healthy eating, regular physical activity, no smoking, adequate sleep, and maintaining healthy weight, cholesterol, blood sugar, and blood pressure. Each component is scored from 0 to 100, with higher scores indicating better cardiovascular health, and the results are combined into an overall index.

The study’s most notable finding was a clear association between being a “night owl” and poorer overall cardiovascular health. Kianersi noted that night owls may be more likely to maintain unhealthy habits or carry cardiovascular risk factors such as poor diet, low activity or smoking, and that the association appeared stronger in women.

Compared with the intermediate group, those in the evening-active group were about 79% more likely to have poorer cardiovascular health, and faced a higher risk of heart attack or stroke, according to Kianersi.

Follow-up results and role of lifestyle factors

Sabra Abbott, Associate Professor of Neurology at Northwestern University’s Feinberg School of Medicine and not involved in the study, said evening chronotypes are often accompanied by factors that increase cardiovascular risk, including irregular sleep timing, diet, and inconsistent exposure to light.

Over a follow-up period of nearly 14 years, Abbott said the study found that night owls had a 16% higher risk of cardiovascular events such as heart attack or stroke than the intermediate group.

In contrast, people who described themselves as “early birds” were about 5% less likely to have poor cardiovascular health or unhealthy habits compared with the intermediate group.

Expert guidance: focus on modifiable behaviors

Kristen Knutson, Associate Professor of Neurology at Northwestern University’s Center for Chronobiology and Sleep Medicine, said the findings include positive signals for those with late-night routines, emphasizing that cardiovascular disease is not inevitable for night owls. She encouraged prioritizing sleep and avoiding smoking.

The study also suggested that interventions targeting modifiable risk factors—such as improving sleep quality, quitting smoking, and sustaining a healthy lifestyle—can help reduce cardiovascular risk in this group. Abbott agreed that night owls should not feel compelled to force their circadian rhythms, but should focus on controllable factors.

Kianersi’s advice was to “Start with the basics: get enough sleep, keep a consistent bedtime and wake time as much as possible, and try to get morning light exposure.”

Related evidence on lifestyle changes

Another study in the European Journal of Preventive Cardiology found that adopting similar healthy habits could reduce cardiovascular events such as heart attack and stroke by up to 57%.

The article also highlighted a lifestyle model associated with benefits, including 7–8 hours of sleep, at least 42 minutes of moderate-intensity physical activity, and a healthy diet with a nutrition score ranging from 57.5 to 72.5. It noted that even smaller adjustments—such as adding 5 minutes of sleep, about 1.9 more minutes of activity, and half a serving of vegetables—were associated with extending life expectancy by roughly one year.

Overall, the findings reinforce the role of lifestyle in cardiovascular health and longevity, particularly through changes that are sustainable over time.