NEW DELHI: Adults who stay up late and are most active at night may face significantly poorer cardiovascular health than those who follow a morning-oriented routine, according to a large new study published in the Journal of the American Heart Association.
The prospective study, published online on January 28, analysed data from 322,777 participants in the UK Biobank aged between 39 and 74 years. Researchers found that individuals who identified as “definite evening” types—commonly known as night owls—had substantially worse scores on the American Heart Association’s “Life’s Essential 8” (LE8) cardiovascular health metrics compared to those with earlier sleep-wake preferences.
Night owls recorded 79% worse LE8 scores than people with intermediate chronotypes, while “definite morning” individuals showed a 5% lower prevalence of poor cardiovascular health scores.
The study revealed that nearly three-quarters of the increased cardiovascular disease (CVD) risk among evening types was linked to modifiable lifestyle factors captured in the LE8 framework. These include diet quality, physical activity, smoking, sleep duration and quality, body weight, cholesterol levels, blood glucose, and blood pressure.
“Individuals with an evening chronotype may particularly benefit from targeted interventions addressing cardiovascular risk factors,” the researchers noted.
ROLE OF THE CIRCADIAN CLOCK
Sleep patterns are regulated by the body’s internal circadian timing system. When daily behaviours—such as sleep, eating, and activity—are misaligned with this internal clock, it can negatively affect metabolic and cardiovascular health. Such circadian misalignment, the authors explained, relates to overall cardiovascular health using the LE8 scoring system.
Among the participants (mean age 57 years; 47% men; 96% White), 6% identified as “definite evening” types, 24% as “definite morning” types, and 67% fell into an intermediate category. None had diagnosed cardiovascular disease at the start of the study.
Evening chronotypes consistently showed poorer LE8 scores. The strongest associations were seen with smoking exposure and inadequate sleep. Night owls were 54% more likely to have high nicotine exposure and 42% more likely to experience insufficient sleep. Lower physical activity levels, higher blood glucose, increased body weight, and poorer diet quality were also more common among evening types. In contrast, differences in blood pressure and cholesterol levels were minimal.
LONG-TERM CARDIOVASCULAR OUTCOMES
Over a median follow-up period of 13.5 years, researchers recorded 15,305 cardiovascular events, including 11,036 heart attacks and 7,214 strokes.
Compared to individuals with intermediate chronotypes, those classified as “definite evening” types had a modest but significant increase in cardiovascular risk.
After adjusting for factors such as age, sex, socioeconomic status, shift work, and family history of heart disease, the hazard ratio for total CVD was 1.16 for evening types. Morning types showed no statistically significant increase in risk.
The findings suggest that while being a night owl does not automatically lead to heart disease, it is closely linked with lifestyle patterns that collectively raise cardiovascular risk. Researchers emphasised that improving sleep habits, physical activity, and other modifiable behaviours could help mitigate these risks for people with an evening chronotype.
