If you usually stay up until midnight scrolling, watching TV, or finishing one last task, you may want to pay attention to the clock. Most sleep advice is about duration: get seven to nine hours, and you're doing reasonably well. However, researchers who tracked the sleeping habits of tens of thousands of adults found that one particular bedtime window was associated with the lowest risk of developing cardiovascular disease.
That window was surprisingly narrow: between 10:00 and 10:59 p.m.
That doesn't make 10:37 p.m. a magical bedtime. The study can't prove that moving your bedtime will prevent heart disease. But if you're regularly still scrolling, watching TV, or working after midnight, the findings give you another reason to look at your evening routine
What does research say?
The study, published in the European Heart Journal, examined 88,026 adults from the UK Biobank. Participants were between 43 and 79 years old when their sleep was measured.
Rather than simply asking people when they normally went to bed, researchers used wrist trackers to record their sleep and wake times for seven days. They then followed participants for an average of 5.7 years. During that period, 3,172 people developed cardiovascular disease.
People who fell asleep between 10:00 and 10:59 p.m. had the lowest incidence of cardiovascular disease in the study.
The differences became particularly interesting when researchers compared other bedtimes with that 10-to-11 window. After accounting for factors including age, sex, sleep duration, smoking, blood pressure, diabetes, cholesterol, and body mass index, people who fell asleep:
- between 11 p.m. and midnight had a 12% higher associated risk, and
- at midnight or later had a 25% higher associated risk.
Those figures describe relative differences in risk, not the chance that an individual person will develop heart disease. The researchers also found that the relationship between bedtime and cardiovascular disease appeared stronger in women than in men.
Another reason not to make too much of the early-bedtime result is that relatively few participants fell asleep before 10 p.m., so the evidence for that part of the curve is more limited.
Why does bedtime matter?
Researchers think the answer may involve your circadian rhythm, the roughly 24-hour internal timing system that helps regulate when you feel awake and when you feel sleepy.
Your body clock responds strongly to light and darkness. Experts agree that light reaching your eyes helps synchronize this internal clock with the outside world. Evening light can delay signals associated with sleep, while morning light helps your body prepare for the day. Very late sleep could interfere with this daily rhythm. For example, going to sleep well after midnight could change how much morning light you receive.
There is wider evidence that cardiovascular function follows daily rhythms, too. Research has found that events such as heart attacks and strokes tend to occur more frequently during the morning hours, although sleep, activity and many other factors are involved.
However, while sleep timing could matter, researchers still don't know whether changing your bedtime itself will change your cardiovascular risk.
Should everyone be asleep by 10 p.m.?
Not necessarily. The British Heart Foundation reviewed the research and warned against treating 10 p.m. as a prescription. As this was an observational study, researchers could identify an association but could not prove that changing your bedtime would change your heart-disease risk.
There are also plenty of reasons one person's ideal schedule may differ from another's. Work schedules, age, family responsibilities, medical conditions, and your natural preference for earlier or later sleep can all affect when you realistically go to bed.
The study population is an important factor too. These were UK Biobank participants who were mostly middle-aged or older adults. The findings, therefore, should not be treated as proof that the same one-hour window is ideal for every age group or population.
Don't ignore duration of sleep
The clock is only one piece of the sleep puzzle. The American Heart Association now describes healthy sleep as having several dimensions, including duration, timing, regularity, quality, and how well you function during the day. It also emphasizes that the strongest evidence still supports getting enough sleep in the first place.
For most adults, that generally means around seven to nine hours per night. The American Academy of Sleep Medicine recommends that adults regularly get at least seven hours of sleep to support good health. So, going to bed at 10:30 p.m. and waking at 4:30 a.m. may not be automatically healthier than going to bed later and getting adequate, good-quality sleep.
A more useful way to use the “golden hour”
Instead of treating 10 to 11 p.m. as a medical deadline, consider the study a reminder that when you sleep matters along with how long you sleep.
If a 10-to-11 bedtime fits naturally into your schedule, it is a reasonable window to aim for. More importantly, try to keep your bedtime and wake time fairly consistent. Most medical practitioners recommend going to bed and waking up at roughly the same time each day and limiting large differences between weekday and weekend schedules. Other recommendations include reducing bright artificial light before bed, keeping your bedroom cool, quiet, and dark, and avoiding caffeine late in the day if it interferes with your sleep.
So, yes, researchers did find an intriguing one-hour “sweet spot.” But the most useful takeaway isn't that everyone needs to be asleep at exactly 10 p.m.; it's that a regular sleep schedule, enough hours of sleep, and a bedtime that works with your body's normal rhythm may deserve as much attention as the alarm you set for the morning.