Middle-aged and older adults who are naturally more active in the evenings have poorer cardiovascular health compared to peers without a strong morning or evening preference, with women showing particularly strong effects. The research, published in the Journal of the American Heart Association, analyzed data from over 300,000 UK Biobank participants and found evening chronotypes had a 79% higher prevalence of poor cardiovascular health scores and a 16% higher risk of heart attack or stroke over approximately 14 years.
Cardiovascular health was measured using the American Heart Association's Life's Essential 8 metrics, which assess health behaviors and factors including diet, physical activity, smoking status, sleep quality, weight, cholesterol, blood sugar, and blood pressure. The study found that about 8% of participants identified as "definitely evening people," characterized by late-night bedtimes and peak activity later in the day, while 24% were "definitely morning people" with earlier activity patterns and bedtimes.
Lead author Sina Kianersi, Ph.D., D.V.M., explained that "evening people often experience circadian misalignment, meaning their internal body clock may not match the natural day-to-night light cycle or their typical daily schedules." This misalignment appears to contribute to behaviors that negatively impact cardiovascular health, including poorer diet quality, smoking, and inadequate or irregular sleep. The research indicated that much of the increased heart disease risk among evening types was attributable to these modifiable factors, particularly nicotine use and insufficient sleep.
Kristen Knutson, Ph.D., FAHA, who chaired the 2025 American Heart Association statement on circadian health, noted that "evening types aren't inherently less healthy, but they face challenges that make it particularly important for them to maintain a healthy lifestyle." The findings suggest that targeted interventions could help evening chronotypes improve their cardiovascular outcomes by addressing specific lifestyle factors. The American Heart Association's scientific statement recommends considering individual chronotype when timing interventions or treatments, as some medications work best when aligned with specific circadian rhythms.
Study limitations include the predominantly white and generally healthier UK Biobank population, which may limit generalizability to other groups, and the reliance on self-reported chronotype data collected only once. The research was partially funded by the American Heart Association, with additional financial information available at https://www.heart.org/en/about-us/aha-financial-information. The full manuscript is accessible at https://www.ahajournals.org/doi/10.1161/JAHA.125.034567.
These findings highlight the importance of considering circadian preferences in cardiovascular health strategies and suggest that helping evening chronotypes improve lifestyle habits could significantly reduce their risk of heart attack and stroke. The research underscores that while chronotype may influence health behaviors, the associated risks are largely modifiable through targeted lifestyle interventions.
