Irregular sleep is linked with a higher risk of death. In a Frontiers in Medicine study of 7,604 US adults, published 29 September 2026, people whose bedtime varied by more than 90 minutes from night to night had a 29% higher risk of dying during about seven years of follow-up. It is an association, not proof of cause.
Key takeaways
- A prospective cohort study in Frontiers in Medicine (Bai, Chen, Cui and Yang, published 29 September 2026) tracked 7,604 US adults who wore a wrist accelerometer for 4 to 7 days in the National Health and Nutrition Examination Survey (NHANES) 2011–2014; 714 died over a median of 81 months.
- Adults whose bedtime varied by more than 90 minutes across nights had a 29% higher risk of death than those whose bedtime varied by 90 minutes or less.
- Each extra hour of night-to-night variation in the middle of sleep was linked with a 22% higher risk of death, after adjusting for age, smoking, weight, blood pressure, diabetes and more.
- The one change: give sleep a fixed window on the plan, with the same bedtime and wake time on workdays and days off.
What did the 2026 study on irregular sleep find?
The more a person’s sleep timing moved around from night to night, the higher their risk of dying during follow-up. The link held for night-to-night variation in bedtime, in the middle of sleep and in how long people slept.
The team, from Taiyuan Central Hospital in China, used minute-by-minute wrist-device data from adults aged 20 and older in NHANES, a nationally representative US survey, with deaths tracked to the end of 2019.
| Measure of irregular sleep | Linked risk of death from any cause |
|---|---|
| Bedtime varying by more than 90 minutes (vs 90 minutes or less) | 29% higher |
| Each extra hour of variation in the middle of sleep | 22% higher |
| Each extra hour of variation in bedtime | 19% higher |
| Each extra hour of variation in sleep length | 17% higher |
| Each 10 points lower on the Sleep Regularity Index | 29% higher |
The same pattern appeared for deaths from cardiovascular disease: each extra hour of variation in the middle of sleep was linked with a 21% higher risk.
How irregular is the average adult’s sleep?
More than most people guess. Bedtime varied by about 1.6 hours among survivors and 1.85 hours among those who died.
The Sleep Regularity Index scores how often you are asleep or awake at the same minute on consecutive days; 100 is perfectly regular. Survivors averaged about 63, those who died about 53, and only 8.9% of adults scored 80 or higher.
Does a regular schedule matter more than sleep length?
In this study, regularity was more closely linked with risk than length: irregular timing was linked with higher risk of death, while average sleep length was not linearly linked with it.
That echoes earlier work. In a 2024 Sleep study of 60,977 UK Biobank participants (Windred and colleagues, Monash University), people in the top four groups for sleep regularity had a 20% to 48% lower risk of death than the least regular group, and regularity predicted death better than sleep duration. Length still matters: the American Academy of Sleep Medicine and the Sleep Research Society advise adults to sleep 7 or more hours a night on a regular basis.
Why would irregular sleep affect the heart?
The leading idea: the body clock keeps blood pressure, heart rate, blood sugar and inflammation on a roughly 24-hour schedule set by sleep and wake times. When that timing shifts nightly, those rhythms drift out of step.
In a small lab test in the same paper, blood vessel cells given an irregular timing signal showed weaker clock-gene activity and more inflammation markers. Cells in a dish are not people, so this is a clue, not proof.
In a 2020 Journal of the American College of Cardiology study of 1,992 adults (Huang, Mariani and Redline), bedtimes varying by more than 90 minutes were linked with about 2.1 times the risk of a cardiovascular event over 4.9 years, compared with 30 minutes or less.
What are the limits of the study?
It shows a link, not a cause. Sleep was measured once, over 4 to 7 days, and illness, pain, caregiving or shift work can make sleep irregular and raise risk at the same time.
The authors adjusted for many of these factors, and older age, high blood pressure and diabetes were more strongly linked with death than any sleep measure. In 2023, a National Sleep Foundation expert panel (Sletten and colleagues, Sleep Health) reached consensus that consistent sleep timing is important for health, safety and performance.
What is the one change to make?
Pick a sleep window and keep it within about half an hour, every night of the week. A fixed wake time is the anchor; bedtime follows from it.
- Choose a wake time that works on workdays, then count back 7 to 8 hours for lights-out.
- Keep both times on days off. Sleeping in by two hours on Saturday is a two-hour swing.
- Get outdoor daylight soon after waking; it helps the body clock hold that wake time. More in How to Fix Your Sleep Schedule: Anchor, Light, 15 Min.
- Start a wind-down 30 minutes before lights-out, with screens and work put away; see Working Before Bed and Sleep: What a 2026 Study Found.
- When the clocks change in spring and fall, move bedtime in 15-minute steps; see When Does Daylight Saving Time End in 2026?
Weekday-to-weekend swings are called social jetlag; for students, see Regular Wake Times for Midterms. Persistent trouble sleeping is a reason to see a doctor. Curious whether your body clock runs early or late? Take the Body Clock Type quiz.
Your day on My BodyClock
The day above on My BodyClock shows a regular workday built around one fixed sleep window: lights out at 10:30 PM, up at 6:30 AM, 8 hours, the same on Saturday and Sunday. A daylight walk and breakfast start the morning, a lunchtime walk and an early-evening workout break up the day, and dinner lands at 6:30 PM, followed by family time, guitar, a wind-down and reading under a lamp.
Build your own day around a fixed sleep window, and save it as a template to reuse, in Owaves: My BodyClock on the App Store, or join the Android waitlist.
FAQ
Is it bad to go to bed at different times every night?
It may be. In a 2026 study of 7,604 US adults, bedtimes that varied by more than 90 minutes were linked with a 29% higher risk of death over about seven years, an association rather than proof of cause.
Is a regular sleep schedule more important than sleeping 8 hours?
Both matter. In a 2024 UK Biobank study of 60,977 adults, sleep regularity predicted death better than sleep length, and in the 2026 NHANES study irregular timing, not average sleep length, was linked with higher risk. Adults are still advised to sleep 7 or more hours a night.
How consistent should my bedtime be?
In the 2026 study and a 2020 heart study, higher risks were seen when bedtime varied by more than 90 minutes from night to night. Keeping bedtime and wake time within about 30 minutes leaves a wide margin.
Does sleeping in on weekends count as an irregular schedule?
Yes, a two-hour lie-in on days off adds variation. A 2023 National Sleep Foundation panel noted that weekend catch-up sleep may help when weekday sleep is too short, but a consistent schedule is the goal.
Sources
- Bai J, Chen P, Cui C, Yang L. Night-to-night sleep variability and all-cause and cardiovascular mortality: a prospective cohort study with a complementary in vitro circadian-disruption experiment. Frontiers in Medicine, 29 September 2026;13:1917205. doi:10.3389/fmed.2026.1917205. https://www.frontiersin.org/journals/medicine/articles/10.3389/fmed.2026.1917205/full
- Windred DP, Burns AC, Lane JM, Saxena R, Rutter MK, Cain SW, Phillips AJK. Sleep regularity is a stronger predictor of mortality risk than sleep duration: A prospective cohort study. Sleep, 2024;47(1):zsad253. doi:10.1093/sleep/zsad253. https://pmc.ncbi.nlm.nih.gov/articles/PMC10782501/
- Huang T, Mariani S, Redline S. Sleep Irregularity and Risk of Cardiovascular Events: The Multi-Ethnic Study of Atherosclerosis. Journal of the American College of Cardiology, 2020;75(9):991-999. doi:10.1016/j.jacc.2019.12.054. https://pmc.ncbi.nlm.nih.gov/articles/PMC7237955/
- Sletten TL, Weaver MD, Foster RG, et al. The importance of sleep regularity: a consensus statement of the National Sleep Foundation sleep timing and variability panel. Sleep Health, 2023;9(6):801-820. doi:10.1016/j.sleh.2023.07.016. https://pubmed.ncbi.nlm.nih.gov/37684151/
- Watson NF, Badr MS, Belenky G, et al. Recommended Amount of Sleep for a Healthy Adult: A Joint Consensus Statement of the American Academy of Sleep Medicine and Sleep Research Society. Sleep, 2015;38(6):843-844. doi:10.5665/sleep.4716. https://pmc.ncbi.nlm.nih.gov/articles/PMC4434546/
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