How regular is your sleep?

A one-week check of your own sleep timing, what the most regular sleepers did, and what a study of 60,977 adults found about regular sleep and the risk of dying. Sources are linked throughout.

The short version

• On most days, the most regular group of sleepers fell asleep and woke up within about a 1-hour window. The least regular group did so within about a 3-hour window.
• For a rough check of your own, note when you fall asleep and wake up for 7 days, weekend included, and see whether most days fall within an hour.
• Compared with the least regular group, the most regular group had a 30% lower risk of dying over about 6 years.
• How regular people's sleep was told more about their risk of dying than how long they slept.
• This is one follow-up study, so it can't show that irregular sleep causes early death.

Check your sleep timing in a week

In the study, people with the most regular sleep went to sleep and woke up within about 1-hour windows on most of their 7 tracked days. People with the least regular sleep did so within about 3-hour windows (Windred, 2024).

1. For 7 days in a row, including a weekend, note roughly when you fall asleep and when you wake up.
2. Look at your times for falling asleep. If most of them fall within about an hour of each other, that's like the most regular group in the study. If they spread over about 3 hours, that's like the least regular group.
3. Do the same for your waking times.

This is a rough check. The study measured regularity with a wrist device and a score that also counts naps and waking in the night, so a diary can't place you in one of its groups or tell you your risk.

For people who have one main sleep a day, the authors suggest that aiming to fall asleep within a 1-hour window, and wake up within another, may be a practical way to make sleep more regular. They add that waking up during the night and broken sleep also count against regularity (Windred, 2024). The study didn't test whether changing your sleep times changes your risk.

The study of 60,977 adults

Researchers used UK Biobank, a large study of UK adults. 60,977 people, average age 63, wore a wrist device for 7 days between 2013 and 2016 that tracked when they were asleep or awake. The researchers scored how alike each day's pattern of sleep and waking was to the next day's, split them into 5 equal groups from least to most regular, and followed people for about 6 years, during which 1,859 died (Windred, 2024).

The fullest analysis used the 46,721 people with complete data. After allowing for age, sex, ethnicity, physical activity, income and deprivation, social contact, smoking, where people lived, shift work and medicine for cholesterol or blood pressure, the risk of dying compared with the least regular group was:

• 20% lower in group 2
• 25% lower in group 3
• 28% lower in group 4
• 30% lower in group 5, the most regular

These compare the rate of death during the study between groups. A 30% lower rate isn't 30 fewer deaths in every 100, and it doesn't show that changing your sleep would change your risk (Windred, 2024, table 2).

Allowing only for age, sex and ethnicity, the most regular group had a 48% lower risk. The authors say the true size of the link likely lies between the two, because some factors in the fuller model, like smoking, could either muddy the comparison or sit on a path from sleep to health, if such a path exists.

Regularity and sleep length

The researchers also split people into 5 equal groups by how long they slept. Sleep regularity predicted the risk of dying better than sleep length did. With both in the same analysis, the most regular group had a 26% lower risk of dying than the least regular group, and the longest sleepers a 16% lower risk than the shortest sleepers (Windred, 2024).

Other sleep habits linked to heart disease and stroke

A separate UK Biobank study followed 385,292 adults without heart disease or stroke for a median of 8.5 years. It scored five sleep habits: being a morning person, sleeping 7 to 8 hours, rarely having insomnia, not snoring and not often feeling very sleepy in the day. People with all five had a 35% lower risk of getting heart disease or a stroke, counted together, than people with none or one (Fan, 2020). Sleep regularity wasn't one of the five.

How far to trust these numbers

• Both studies watched people as they were. Nobody was asked to change their sleep, so neither can show that sleep habits cause the differences. Only the study of 60,977 adults looked at sleep regularity and deaths.
• Its authors say irregular sleep may be both a cause of a higher risk of dying and a marker of it, and the study can't tell which.
• In that study, sleep was tracked for one week only, which is a snapshot of each person's habits.
• Its people were UK adults aged about 43 to 79, almost all of them white, so the results may not hold for everyone.

Sources

• Windred et al. Sleep regularity is a stronger predictor of mortality risk than sleep duration: a prospective cohort study. Sleep, 2024.
• Fan et al. Sleep patterns, genetic susceptibility, and incident cardiovascular disease: a prospective study of 385 292 UK biobank participants. Eur Heart J, 2020.