Early Birds, Night Owls, and Your Heart
It’s not just about how much sleep you get, but when you get it. According to research published on November 9 in the cardiology journal European Heart Journal, British scientists looking at the relationship between sleep onset time and cardiovascular risk have pinpointed a specific window that could be kind to your heart: falling asleep between 10 p.m. and 11 p.m.
The study, led by the University of Exeter, analyzed health data from over 88,000 UK adults aged 43 to 79, sourced from the UK Biobank (a large biomedical database). Participants wore a connected bracelet for a week, recording the precise time they fell asleep and woke up. They answered detailed lifestyle questionnaires—covering socio-economic status, sleep habits, smoking—plus information on their health and body (BMI, diabetes, cholesterol, and so on). Then, just to keep things suspenseful, their hearts were monitored for six years.
What Did They Find?
At the end of the follow-up, 3,172 people (or 3.6% of those involved) developed cardiovascular disease. The most striking result? It was the night owls who took the biggest hit. Falling asleep at midnight or later raised the risk of heart issues by 25%. But don’t get too smug, early sleepers: dozing off before 10 p.m. wasn’t much better, with risk hovering at 24%. The lucky few? Those who hit the hay between 10:00 and 10:59 p.m. saw the lowest rates.
Why Does Timing Matter?
So, what’s behind this sleep-time sweet spot? British researchers suspect that disrupting our internal body clock—by going to bed either too early or too late—throws things out of balance.
“These disruptions to behavior and our circadian clock increase inflammation and can affect glucose regulation, two factors that can raise the risk of cardiovascular disease,” explains David Plans, a neuroscience researcher and lead author of the study.
Sleep medicine doctor Philippe Beaulieu, who reviewed the research, wasn’t surprised by the findings. In his view, late bedtimes are the most damaging because they rob you of the regenerative effects of those precious first hours of sleep. As he puts it:
“During phases of light to deep sleep, the body carries out cardiovascular recovery: heart rate and blood pressure drop significantly. If sleep falls short in either quantity, quality, or both, these restorative processes just can’t do their job, leaving us more exposed to heart problems.”
And just so you’re not tempted to play catch-up the next morning: going to bed late doesn’t guarantee a lovely late lie-in. Quite the opposite. As Dr. Beaulieu notes:
“If the night owl also ends up cutting their sleep short, they’re setting themselves up for chronic self-inflicted sleep deprivation—and that, in turn, boosts cardiovascular risk.”
Extra Risk Factors and What You Can Do
There’s a twist: according to British researchers, women in the study seemed even more affected. No one is entirely sure why. As David Plans suggests:
“There may be a difference between the sexes in how the endocrine system responds to disruptions in circadian rhythm.”
And since the study subjects were all aged 43–79, age (and things like menopause) may play a role, too, as Dr. Beaulieu says. Still, while the findings are promising, they’re not a smoking gun. The results show a correlation between sleep onset time and cardiovascular risk, but they don’t prove cause and effect. The researchers are keen to keep digging, with plans for studies on sleep quality and with more representative samples. Keep in mind: everyone in this study was middle-aged or older.
In the meantime, Dr. Beaulieu suggests you avoid “extreme” sleep schedules—so no nodding off at 6 p.m. or pulling all-nighters until after 3 a.m. Instead, focus on your wake time and make it as regular as possible. Here’s his simple advice:
“Wake-up time should be consistent, and it ought to be marked each time by two powerful cues: some muscular activity (like a walk or stretching) and exposure to natural light as soon as you get up. If you stick to this, your bedtime should naturally fall into place.”
And as a tongue-in-cheek aside, there’s skepticism about the merits of shifting the clocks for daylight saving time (with the British, by the way, having side-stepped that particular headache).
John is a curious mind who loves to write about diverse topics. Passionate about sharing his thoughts and perspectives, he enjoys sparking conversations and encouraging discovery. For him, every subject is an invitation to discuss and learn.
