- A large UK study found that people who naturally go to bed late and wake late had a modestly higher risk of heart attack or stroke over time.
- Much of that extra risk appeared to be explained by overall cardiovascular health behaviours and factors such as smoking, sleep, weight, diet, and blood glucose.
- The takeaway is not that being a “night owl” dooms you, but that improving modifiable habits could offset most of the risk.
Cardiovascular disease remains a leading cause of death worldwide.
Alongside diet, activity, and smoking, sleep is now recognised as a key part of heart health.
One way to think about sleep timing is “chronotype”. Chronotype describes whether you naturally function best earlier in the day (morning type) or later (evening type).
Evening chronotypes may experience more “circadian misalignment”. That means their internal body clock can be out of sync with work schedules and social routines.
Circadian disruption is linked to changes in hormones, the nervous system, and metabolism.
It can also influence behaviours like smoking, alcohol intake, and diet quality.
Researchers explored this using UK Biobank, following adults aged 39 to 74 with no prior history of heart attack or stroke at baseline.
Chronotype was self-reported, and overall cardiovascular health was measured using the American Heart Association’s Life’s Essential 8 (LE8) score.
LE8 combines several components of heart health, including:
- diet
- physical activity
- nicotine exposure
- sleep
- body weight
- blood lipids
- blood glucose
- blood pressure
Higher scores indicate better cardiovascular health.
Participants were followed for a median of 13.8 years.
During that time, many people experienced a first cardiovascular event, defined as a heart attack or stroke.
Most participants described themselves as an “intermediate” chronotype.
A smaller group identified as “definitely evening”.
People with a definite evening chronotype tended to have slightly lower LE8 scores on average.
Poorer LE8 scores were especially linked to nicotine use and insufficient sleep.
Compared with intermediate chronotypes, evening chronotypes had a higher risk of cardiovascular disease over the follow-up period.
The increase was about 16% in the study’s adjusted models.
The researchers then looked at how much of this association could be explained by LE8.
They estimated that around three-quarters of the evening chronotype’s increased risk was mediated through LE8 factors.
Smoking appeared to be the single largest mediator. In the modelling, nicotine use accounted for roughly a third of the association.
Other factors such as sleep, blood glucose, body weight, and diet each contributed a meaningful share.
In simple terms, late sleepers were more likely to have a cluster of risk factors that raise cardiovascular risk.
This does not prove that being an evening chronotype causes heart disease.
It does, however, support the idea that chronotype can be a useful flag for where extra prevention effort might help.
The study has limitations worth taking seriously.
- Sleeping under 7 hours is strongly linked to shorter life expectancy
- Sleep apnoea risk may be linked with poorer mental health in adults over 45
- High intensity yoga shows strongest link for better sleep
Chronotype was measured using a single question, and both chronotype and LE8 were assessed at one point in time.
The UK Biobank population is also not fully representative of the whole UK.
It is, on average, healthier and less diverse than the general population, which can limit generalisability.
Still, the practical implication is clear.
If you are a late sleeper, focusing on the basics – quitting smoking, protecting sleep duration and regularity, improving metabolic health, and maintaining a healthy weight – could reduce much of the added risk.
Study reference: Journal of the American Heart Association (2026), “Chronotype, Life’s Essential 8, and Risk of Cardiovascular Disease: A Prospective Cohort Study in UK Biobank”, DOI: 10.1161/JAHA.125.044189.
