Adults who fell asleep between 10 and 11 p.m. had the lowest rate of new heart disease in a UK Biobank study of more than 88,000 people. Both earlier and later bedtimes were tied to a higher rate of cardiovascular events.
The observational study, published in November 2021 in European Heart Journal - Digital Health, used wrist-worn accelerometers to record sleep for seven days in participants aged 43 to 79. The team then followed them for an average of 5.7 years.
Compared with the 10 p.m. to 11 p.m. window, sleep onset after midnight carried a 25 percent higher risk of new cardiovascular disease. Falling asleep before 10 p.m. was linked to a 24 percent higher risk, and the 11 p.m. to midnight slot to a 12 percent higher risk. The relationship formed a U-shape and held up after adjusting for sleep duration and irregular sleep patterns. The signal was stronger in women than in men.
Why timing matters, not just hours
Sleep onset time may line up more closely with the body's 24-hour clock than sleep duration alone. When bedtime drifts too far outside that window, the hormonal and metabolic recovery that normally happens overnight can misfire. The UK Biobank authors describe their finding as suggestive, not conclusive, and note the association was particularly clear for women.
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Because this was an observational study, it cannot prove that a late bedtime causes heart disease. It can only show the two travel together.
How your body clock shifts with age
The internal clock is not fixed. According to the Sleep Foundation, circadian rhythms peak in lateness during adolescence, which is why teenagers naturally resist early bedtimes. The pattern then reverses in later life. Starting around age 60 to 65, rhythms shift earlier, a change researchers call phase advance.
That is why many older adults get sleepy in the early evening and wake before dawn even when they try to stay up later.
Practical bedtime by age
The table below combines the National Sleep Foundation's sleep duration guidance with typical wake times to give a rough bedtime target. It is a starting point, not a prescription.
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Age group | Recommended sleep | Typical bedtime window |
|---|---|---|
Teens (14-17) Also read: The best time of day to exercise based on your sex | 8-10 hours | 10 to 11 p.m. for a 7 a.m. wake, though biology pulls later |
Young and middle-aged adults (18-64) | 7-9 hours Also read: If you drink alcohol, the type you choose may affect your heart risk | 10 to 11 p.m. for a 6 to 7 a.m. wake |
Older adults (65+) | 7-8 hours | 9 to 10 p.m. as rhythms shift earlier Also read: 8 in 10 young cancer patients found it themselves. Doctors missed the signs |
Teenagers are the group most out of sync with school schedules. The Sleep Foundation notes that fewer than two in ten meet the recommended range on school nights, in part because their circadian rhythms start to shift later after childhood, pushing natural sleep onset toward midnight.
Finding your chronotype
Not every adult fits the 10 to 11 p.m. window. Chronotype, a person's natural preference for early or late sleep, varies widely. Sleep researcher Michael Breus groups people into four types, with the majority sitting somewhere in the middle and smaller groups leaning strongly early or strongly late. Two validated questionnaires, the Morningness-Eveningness Questionnaire and the Munich ChronoType Questionnaire, can help you find where you sit.
Nudging bedtime earlier
Jumping your bedtime forward by a full hour rarely works. Sleep clinicians advise moving it in 15-minute steps every few nights while keeping the wake time steady. Bright morning light, dim evenings and cutting screen use in the last hour before bed all help pull the internal clock earlier.
For most working-age adults, aiming to be asleep between 10 and 11 p.m. lines up with both the UK Biobank finding and standard adult sleep guidance of seven to nine hours a night. Anyone with persistent trouble falling asleep or staying asleep should raise it with their doctor.
This article is made and published by Jesper Bengtson, who may have used AI in the preparation.