People with evening chronotype may have poorer heart health

Middle aged or older people with an evening chronotype are at increased risk of cardiovascular disease (CVD), owing to their unfavourable cardiovascular health profile, according to a study.

In a large cohort of UK Biobank participants followed over a median of 13.8 years, the risk of incident CVD (ie, first myocardial infarction [MI] or stroke) was 16-percent higher for those who considered themselves to be a “definitely evening” person (evening chronotype) vs those who fell somewhere in between the “definitely evening” and “definitely morning” categories (intermediate chronotype) (hazard ratio [HR], 1.16, 95 percent confidence interval [CI], 1.10–1.22). [J Am Heart Assoc 2026;doi:10.1161/JAHA.125.044189]

On the other hand, the risk did not significantly differ between participants who reported being a “definitely morning” person (morning chronotype) and those with an intermediate chronotype (HR, 1.03, 95 percent CI, 0.99–1.07).

“Similar findings were observed for MI and stroke individually or when alternative chronotype groupings were used, excluding ‘Don’t know’ responses,” said first study author Dr Sina Kianersi from Brigham and Women’s Hospital and Harvard Medical School in Boston, Massachusetts, US.

Kianersi noted that the observed association between evening chronotype and elevated CVD risk was largely driven by lower attainment of Life’s Essential 8 (LE8) cardiovascular health metrics.

In mediation analysis, a poor overall LE8 score explained 75 percent of the association between evening chronotype and CVD (HR, 1.11, 95 percent CI, 1.09–1.13). When each LE8 component was assessed individually, nicotine exposure emerged as the strongest mediator, accounting for 34 percent of the association, followed by sleep (14 percent), blood glucose (12 percent), body weight (11 percent), and diet (11 percent).

Poor cardiovascular health

Formulated by the American Heart Association (AHA) to provide a checklist for cardiovascular health, LE8 include sleep duration, dietary quality, participation in physical activity, exposure to nicotine/cigarette smoking, and measures of BMI, fasting blood glucose, total cholesterol, and blood pressure (BP) levels. LE8 scores ranged from 0 to 100, with higher scores indicating better cardiovascular health. [Circulation 2022;doi:10.1161/CIR.0000000000001078]

The mean LE8 score in the cohort was 67, and 7 percent of the participants had a score of <50, indicating poor cardiovascular health. The prevalence of a poor cardiovascular health profile was 79-percent higher among participants with an evening chronotype (prevalence ratio, 1.79, 95 percent CI, 1.72–1.85) and 5-percent lower among those with a morning chronotype (prevalence ratio, 0.95, 95 percent CI, 0.93–0.98) relative to participants with an intermediate chronotype.

Compared with intermediate, evening chronotype was associated with a higher likelihood of having poor scores in six of the LE8 components, except for BP and total cholesterol. The strongest associations were seen for nicotine exposure (prevalence ratio, 1.54, 95 percent CI, 1.50–1.58) and inadequate sleep (prevalence ratio, 1.42, 95 percent CI, 1.36–1.48).

Looking at sex-related difference, evening chronotype was more strongly associated with poor cardiovascular health profile in women (prevalence ratio, 1.96, 95 percent CI, 1.85–2.08) than in men (prevalence ratio, 1.67, 95 percent CI, 1.60–1.75; p=0.0005 for interaction).

Kianersi noted that some of these cardiovascular health measures in LE8 are influenced by the universal circadian timing system.

“‘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,” Kianersi said. He explained that individuals with an evening chronotype may therefore experience irregular eating schedules, lower levels of physical activity, and inadequate or irregular sleep. 

Circadian disruptions can also trigger inflammation, endothelial dysfunction, and disruption in heart rate. Additionally, it increases the likelihood of mental illness, which in turn raises the risk of CVD. [Nat Rev Cardiol 2019;16:437-447; Circ Res 2024;134:770-790; Curr Psychiatry Rep 2018;20:59; Mol Psychiatry 2025;30:1-13]

Opportunity for improvement

In an AHA press statement, Dr Kristen Knutson, volunteer chair of the 2025 AHA statement “Role of Circadian Health in Cardiometabolic Health and Disease Risk,” pointed out that the factors driving the CVD risk among participants with an evening chronotype are modifiable.

“Therefore, evening types have options to improve their cardiovascular health. [They] aren’t inherently less healthy, but they face challenges that make it particularly important for them to maintain a healthy lifestyle,” said Knutson, who was not involved in the study.

She emphasized that individual chronotype should guide the timing of interventions or treatment.

“Some medications or therapies work best when they align with a specific time of relevant circadian rhythms, and this time will vary depending on whether you are a morning, intermediate, or evening chronotype,” Knutson said. “Targeted programs for people who naturally stay up late could help them improve their lifestyle behaviours and reduce their risk of CVD.”

The study included 322,777 UK Biobank participants (mean age 57 years, 47 percent male, 96 percent White, 58 percent had a family history of CVD). Of these, 8.3 percent had an evening chronotype, 24.2 percent had a morning chronotype, and 67.5 had an intermediate chronotype.

Compared with participants with an intermediate chronotype, those with an evening chronotype were younger, had lower socioeconomic status, were more likely to hold a college or university degree (43 percent vs 37 percent), more frequently engaged in shift work (12 percent vs 9 percent), and had a lower overall LE8 score (65 vs 68).