Middle-aged and older adults who naturally prefer evening activity face substantially higher cardiovascular risks compared to those with morning or intermediate chronotypes, according to research published in the Journal of the American Heart Association. The study, analyzing data from over 300,000 UK Biobank participants with an average age of 57, found that self-identified "definitely evening people" had a 79% higher prevalence of poor cardiovascular health scores and a 16% increased risk of heart attack or stroke over approximately 14 years of follow-up.
Cardiovascular health was measured using the American Heart Association's Life's Essential 8 metrics, which assess health behaviors and factors including diet quality, physical activity, smoking status, sleep quality, weight, cholesterol, blood sugar, and blood pressure. Researchers found that the increased cardiovascular risk among evening chronotypes was particularly pronounced in women, suggesting gender-specific vulnerabilities in how circadian preferences interact with heart health.
Lead researcher Sina Kianersi, Ph.D., D.V.M., of Brigham and Women's Hospital and Harvard Medical School, 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 unhealthy behaviors that directly impact cardiovascular outcomes, with the study identifying nicotine use and inadequate sleep as particularly significant factors driving the increased risk.
The research revealed that approximately 8% of participants identified as "definitely evening people," characterized by late-night bedtimes and peak activity later in the day, while 24% identified as "definitely morning people" with earlier activity patterns and bedtimes. The remaining 67% fell into an intermediate category without strong morning or evening preferences. Morning chronotypes actually showed a 5% lower prevalence of poor cardiovascular health scores compared to intermediate types, suggesting potential protective effects of morning-oriented circadian rhythms.
Despite the concerning findings, researchers emphasize that the risks associated with evening chronotypes are largely modifiable. Kristen Knutson, Ph.D., FAHA, who chaired the American Heart Association's 2025 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 addressing specific lifestyle factors could substantially reduce cardiovascular risks for evening-oriented individuals.
The study's implications extend beyond individual behavior modification to potential clinical applications. The American Heart Association scientific statement suggests that individual chronotype should be considered when timing medical interventions or treatments, as "some medications or therapies work best when they align with a specific time of relevant circadian rhythms." This chronotype-aware approach to healthcare could optimize treatment effectiveness across different circadian profiles.
Researchers acknowledge several limitations, including the UK Biobank's predominantly white and generally healthy participant pool, which may limit generalizability to more diverse populations. Additionally, chronotype assessment relied on single-timepoint self-reporting rather than objective measurements. The study was partially funded by the American Heart Association, with complete funding information available in the published manuscript accessible through the Journal of the American Heart Association at https://www.ahajournals.org/doi/10.1161/JAHA.125.034567.
For those interested in assessing their own cardiovascular health, the American Heart Association provides the Life's Essential 8 My Life Check Calculator at https://www.heart.org/en/healthy-living/healthy-lifestyle/my-life-check--lifes-simple-7. The broader implications of this research suggest that recognizing and accommodating individual circadian differences could become an important component of cardiovascular disease prevention strategies, particularly for the substantial minority of adults with strong evening preferences.
