If you naturally stay up late and struggle with early mornings, you may be among the roughly 8% of adults classified as having an “evening chronotype.” New research published in the Journal of the American Heart Association suggests this preference for late nights comes with a notable downside: a 16% higher risk of cardiovascular disease compared to people with intermediate sleep timing preferences. However, the study also delivers an encouraging message: most of this elevated risk appears to stem from modifiable lifestyle factors rather than the chronotype itself.
What the Research Showed
Researchers from Brigham and Women’s Hospital, Harvard Medical School, and collaborating institutions analyzed data from 322,777 participants in the UK Biobank, a large population study of adults aged 39 to 74 who were free of cardiovascular disease at enrollment. Participants were followed for a median of nearly 14 years, during which time 17,584 experienced a heart attack or stroke.
The study examined how chronotype relates to the American Heart Association’s Life’s Essential 8, a comprehensive measure of cardiovascular health that includes four health behaviors (diet, physical activity, nicotine exposure, and sleep duration) and four health factors (body weight, blood lipids, blood glucose, and blood pressure). Each component is scored from 0 to 100, with higher scores indicating better cardiovascular health.
Participants who identified as “definite evening” types had substantially worse cardiovascular health profiles across nearly all measures. They were 79% more likely to have poor overall cardiovascular health compared to those with intermediate chronotypes. The strongest associations appeared for nicotine exposure, where evening types were 54% more likely to have poor scores, and inadequate sleep duration, where they were 42% more likely to fall short of recommendations.
The Critical Finding: Lifestyle Explains Most of the Risk
Perhaps the most clinically significant finding was that 75% of the association between evening chronotype and cardiovascular disease was explained by the Life’s Essential 8 factors. When researchers conducted mediation analyses to determine how much of the increased heart disease risk could be attributed to these modifiable factors, nicotine exposure emerged as the single strongest contributor, accounting for 34% of the association. Sleep quality contributed 14%, blood glucose 12%, body weight 11%, and diet 11%.
After accounting for all eight cardiovascular health components, no direct effect of evening chronotype on cardiovascular disease remained. This suggests that the chronotype itself may not directly damage the heart and blood vessels. Rather, being a night owl appears to set the stage for behaviors and metabolic patterns that accumulate over time to increase cardiovascular risk.
Why Night Owls May Struggle with Healthy Habits
The researchers propose several mechanisms to explain why evening chronotypes tend to have worse cardiovascular health. People whose internal clocks run late often experience what scientists call circadian misalignment, a mismatch between their biological preferences and the demands of work schedules and social obligations that typically favor early risers.
This misalignment can disrupt behavioral rhythms, affecting eating patterns, physical activity levels, and sleep regularity. Evening types may eat meals at irregular times, be less physically active during conventional hours, and accumulate sleep debt when forced to wake early for work despite going to bed late. Extended late-night light exposure can further delay melatonin secretion, compounding these disruptions.
Research has also linked circadian disruption to higher rates of depression and anxiety, which are themselves independent risk factors for cardiovascular disease. At the molecular level, misalignment can affect clock genes that regulate metabolic pathways in the liver, pancreas, and cardiovascular system, potentially contributing to inflammation, insulin resistance, and dysregulation of blood pressure.
What This Means for Night Owls
The study’s authors emphasize that their findings should not be interpreted as a reason for evening types to feel helpless about their cardiovascular health. To the contrary, the results highlight that interventions targeting the specific risk factors measured by Life’s Essential 8 may be particularly beneficial for this population.
For night owls concerned about heart health, the data suggest focusing on the factors that showed the strongest associations with chronotype: avoiding tobacco and secondhand smoke, maintaining adequate sleep duration despite schedule challenges, managing blood glucose through diet and activity, maintaining a healthy weight, and eating a nutritious diet. Blood pressure and cholesterol showed weaker associations with chronotype, suggesting these may be less influenced by sleep timing preferences.
The association between evening chronotype and poor cardiovascular health was notably stronger among women than among men in this study, with women showing a 96% higher prevalence of poor overall scores than men did (67%). This suggests that interventions may need to account for sex differences in how chronotype affects health behaviors.
Study Strengths and Limitations
The research benefits from its large sample size, long follow-up period, and use of objective measurements for several health factors, including blood pressure, blood lipids, and blood glucose. The prospective design, following participants forward in time from baseline, strengthens the ability to draw conclusions about temporal relationships between chronotype and subsequent disease.
However, the study has limitations. Chronotype was assessed with a single question rather than a comprehensive questionnaire, though this measure has been validated against longer instruments. The UK Biobank population is predominantly White and healthier than the general population, which may limit generalizability. Additionally, because both chronotype and the Life’s Essential 8 components were measured at the same time point, the study cannot definitively establish that chronotype preceded the development of poor health behaviors.
The Bottom Line
This research adds to growing evidence that when we sleep matters for health, not just how long we sleep. For the millions of adults who naturally gravitate toward late nights, the findings offer both a warning and a reassurance. Evening chronotype does appear to be associated with increased cardiovascular risk, but this risk is not inevitable. By paying particular attention to smoking avoidance, sleep adequacy, weight management, and other components of cardiovascular health, night owls may be able to substantially reduce or eliminate the excess risk associated with their sleep timing preferences.
The study’s authors conclude that evening chronotype should be considered a clinically relevant factor when developing cardiovascular disease prevention strategies, with targeted promotion of healthy behaviors among people who identify as night owls.
