Staying up late increases heart risk

Middle-aged and older adults who are more active at night are more likely to have poorer cardiovascular health than those who are more active during the day. This could be especially true among women, according to new research published in the Journal of the American Heart Associationopen access journal of the American Heart Association.

The researchers reviewed health data from more than 300,000 adults (average age 57 years) participating in the UK Biobank to assess how chronotypes (an individual’s natural preference for sleep-wake schedule) affect their cardiovascular health.

Around the 8% of participants declared themselves “definitely night people,” which was characterized by going to bed late (e.g., at 2.00 early morning) and reach their peak of activity later in the day.

People who reported themselves as “definitely early risers”—that is, more active earlier in the day and going to bed earlier (e.g., at 09.00 of the night) represented approximately 24% of the participants. Around the 67% of participants were classified as having “intermediate” chronotype if they were unsure or if they indicated that they were neither early risers nor evening risers.

Cardiovascular health was measured according to the metrics Life’s Essential 8 from the American Heart Association, which identify health habits and factors associated with optimal cardiovascular health. These metrics include a healthy diet, regular physical activity, not smoking, good quality sleep, as well as healthy levels of weight, cholesterol, blood sugar, and blood pressure.

The analysis confirmed that, compared to intermediate chronotypes, “evening” or night owls had a prevalence 79% greater than having an overall score of poor cardiovascular health. Night owls were at risk 16% greater risk of having a heart attack or stroke over an average follow-up of about 14 years, compared with people in the intermediate category.

Especially in women

Evening chronotype was more strongly related to low cardiovascular health scores in women than in men.

Much of the increased risk of heart disease among nocturnal people was due to poor habits and factors related to heart health, especially nicotine use and lack of sleep. On the contrary, early risers had a prevalence of 5% lower heart health scores compared to those who did not have a strong morning or evening chronotype.

“Nocturnal people often experience circadian imbalances, which means that their internal biological clock may not coincide with the natural day-night light cycle or with their usual daily schedules,” says the study’s lead author, Dr. Sina Kianersiresearcher in the division of sleep and circadian disorders at Brigham and Women’s Hospital and Harvard Medical School (United States)–. “Nocturnal people may be more likely to engage in behaviors that affect cardiovascular health, such as poor diet, smoking, and inadequate or irregular sleep.”

“Not everything is bad”

However, the study’s findings aren’t all bad for night owls, he points out. Kristen Knutsonvolunteer chair of the American Heart Association’s 2025 statement ‘The Role of Circadian Health in Cardiometabolic Health and Disease Risk’, who was not involved in this research.

“These findings show that the increased risk of heart disease among nocturnal people is due in part to modifiable behaviors such as smoking and sleep. Therefore, nocturnal people have options to improve their cardiovascular health,” he explains. “Nocturnal people are not inherently less healthy, but face challenges that make it especially important for them to maintain a healthy lifestyle.

The American Heart Association scientific statement that led Knutson suggests that individual chronotype should be taken into account to determine the timing of interventions or treatment.

“Some medications or therapies work best when aligned with a specific schedule of relevant circadian rhythms, and this schedule will vary depending on morning, middle or evening chronotype,” he notes. “Specific programs for people who frequently stay up late could help them improve their lifestyle habits and reduce the risk of cardiovascular disease.”