Regularly staying up late may increase the risk of heart attack or stroke, according to a new study published in the Journal of the American Heart Association. Researchers found that people who are active late at night, often referred to as “night owls,” are more likely to experience poor cardiovascular health compared to early risers.
The study, led by Sina Kianersi of Brigham and Women’s Hospital and Harvard Medical School, analysed data from more than 300,000 adults, with an average age of 57, to assess how sleeping patterns impact heart health. About eight percent of participants identified themselves as “definitely evening people,” typically going to bed late and reaching peak activity levels later in the day.
Night owls were found to have a 16 percent higher risk of heart attack or stroke compared to early risers. The research also showed that late sleepers had a 79 percent higher prevalence of poor cardiovascular health. Cardiovascular health was assessed by measuring blood pressure, cholesterol, blood sugar, and weight, as well as lifestyle factors including diet, exercise, smoking, and sleep quality.
“Evening people often experience circadian misalignment, meaning their internal body clock may not match the natural day-to-night cycle or their typical daily schedules,” Kianersi said. He added that night owls are more likely to engage in behaviours that can negatively affect heart health, such as poor diet, smoking, and insufficient sleep.
The study also found that the link between late sleeping and poor cardiovascular health was stronger among women. However, the researchers noted limitations, including the fact that chronotype—whether someone is a morning or evening person—was based on a single self-reported question, which may not capture changes over time or could lead to misclassification.
Health experts say the findings highlight the importance of modifiable behaviours in reducing heart risks. “The higher heart disease risks among evening types are partly due to behaviours such as smoking and sleep. Evening types have options to improve their cardiovascular health,” said Kristen Knutson, professor at Northwestern University in Chicago, who was not involved in the research. She added that night owls are not inherently less healthy and that maintaining a balanced lifestyle is crucial.
Targeted programs for individuals who naturally stay up late could help encourage healthier routines and reduce cardiovascular risk. Experts also emphasise the importance of strong circadian rhythms, which regulate sleep, activity, and key body functions. Disruptions to these rhythms—caused by irregular sleep schedules, late-night light exposure, shift work, or jet lag—have been linked to higher risks of obesity, type 2 diabetes, high blood pressure, and heart disease.
The study adds to growing evidence that aligning daily schedules with natural sleep patterns, along with adopting healthy lifestyle habits, can play an important role in protecting heart health, even for those who naturally prefer late nights.
