Night Owls Face Higher Cardiovascular Risk, Particularly Women, Study Finds

Middle-aged and older adults who are naturally more active in the evenings may have worse cardiovascular health compared to peers without a strong morning or evening preference, with this association being particularly pronounced among women. The research, published in the Journal of the American Heart Association, analyzed data from over 300,000 adults in the UK Biobank, finding that unhealthy behaviors among night owls—such as poor diet quality, insufficient sleep, and smoking—largely account for their lower cardiovascular health profile. Cardiovascular health was measured using the American Heart Association’s Life’s Essential 8 metrics, which assess health behaviors and factors like diet, physical activity, smoking status, sleep quality, weight, cholesterol, blood sugar, and blood pressure.

The analysis revealed that compared to intermediate chronotypes, "evening people" had a 79% higher prevalence of poor overall cardiovascular health scores and a 16% higher risk of heart attack or stroke over a median follow-up of about 14 years. Evening chronotype was more strongly related to low cardiovascular health scores in women than in men. In contrast, "morning people" had a 5% lower prevalence of low heart health scores compared to those without a strong chronotype preference. Lead author Sina Kianersi, Ph.D., D.V.M., a research fellow at Brigham and Women’s Hospital and Harvard Medical School, explained that "evening people" often experience circadian misalignment, where their internal body clock may not match natural light cycles or daily schedules, leading to behaviors that can negatively impact cardiovascular health.

However, the findings offer a pathway for improvement, as much of the increased risk was attributed to modifiable factors like nicotine use and inadequate sleep. Kristen Knutson, Ph.D., FAHA, volunteer chair of the 2025 American Heart Association statement on circadian health, noted that evening types have options to improve their cardiovascular health through lifestyle changes. She emphasized that individual chronotype should be considered in medical interventions, as some treatments work best when aligned with specific circadian rhythms. The American Heart Association provides resources such as the Life’s Essential 8 My Life Check Calculator to help individuals assess and improve their health. Study limitations include the UK Biobank’s predominantly white and generally healthier participant pool, which may limit generalizability, and the reliance on self-reported chronotype data measured only once. The research was partially funded by the American Heart Association, with additional details available in the manuscript.