Approximately 75% of the association between evening chronotype and cardiovascular disease risk may be mediated by lower attainment of the American Heart Association’s Life’s Essential 8 cardiovascular health metrics, according to a recent study.
In a prospective analysis of UK Biobank participants, investigators found that adults with a definite evening chronotype had a 16% higher risk of cardiovascular disease, defined as first myocardial infarction or stroke, compared with those with an intermediate chronotype over a median follow-up of 13.8 years. Mediation analyses indicated that approximately 75% of this association was explained by poorer attainment of the American Heart Association’s (AHA) Life’s Essential 8 (LE8) scores, with nicotine exposure as the largest mediator, followed by sleep, blood glucose, body weight, and diet.
The prospective cohort included 322,777 adults aged 39 to 74 years who were free of myocardial infarction and stroke at baseline between 2006 and 2010. Chronotype was assessed at enrollment using a validated single-item question and categorized as definite morning, intermediate, or definite evening. Cardiovascular health was measured using LE8 scores, which comprise four health behaviors (diet, physical activity, nicotine exposure, and sleep) and four health factors (body weight, blood lipids, blood glucose, and blood pressure). Each component was scored from 0 to 100 and averaged to create a composite score, with scores below 50 indicating unfavorable cardiovascular health. Incident cardiovascualr disease events were identified through linkage with hospital admission and death registry records.
After adjustment for sociodemographic factors, shift work, and family history of cardiovascular disease, the participants who had a definite evening chronotype had a 79% higher prevalence of an unfavorable LE8 scores compared with those who had an intermediate chronotype. Poorer scores were observed across six of the eight LE8 components, with the strongest associations seen for nicotine exposure and inadequate sleep.
“Moreover, our prospective findings suggest that the association between evening chronotype and CVD risk is primarily mediated by a poor overall LE8 score,” noted lead study author Sina Kianersi, PhD, DVM, of the Division of Sleep and Circadian Disorders in the Department of Medicine at Brigham and Women’s Hospital and Harvard Medical School, and colleagues.
Several limitations warranted consideration. Chronotype was measured using a single self-reported item at baseline, which may have introduced misclassification despite evidence of validity and long-term stability. LE8 components were assessed concurrently with chronotype, limiting the ability to establish strict temporal sequencing between exposure and mediators, and some components may have changed during follow-up. The UK Biobank cohort consists predominantly of White and generally healthier participants, which may have limited generalizability. Residual confounding also couldn't be fully excluded, although extensive sensitivity analyses supported the robustness of the findings.
Co–study author Martin K. Rutter, MD, disclosed consulting compensation from Eli Lilly and limited stock holdings in GSK, which weren't related to the study. The study authors reported no additional conflicts of interest.