Consistency Beats Sleep Duration: The Key to Healthy Sleep

Koalas sleep 20 hours a day. For humans, duration is less important — anything over six hours is already fine according to a new study. What matters most is that sleep is regular.

Even small changes to your sleep habits can significantly reduce the risk of many diseases in a short time. A new UK Biobank study, analyzing objective sleep data from over 88,000 people, has shown that regular sleep is a much stronger predictor for health outcomes and mortality than mere duration.

For the latter, six hours is considered the lower limit for most adults, with the “sweet spot” at seven to eight hours. Good news for long sleepers: the study disproved earlier observations that more than nine hours of sleep is harmful. The study found that only one disease showed an association with objectively measured long sleep. Roughly 20% of self-reported “long sleepers” in fact slept less than six hours, but simply spent a long time in bed.

Regular Bedtimes – Even on Weekends

With more than six hours of sleep, we are already in the healthy range. More important than sleep duration, however, is when the journey to dreamland begins. According to the study, those with fixed bedtimes and wake‑up times live healthier lives and reduce the risk of over 90 diseases such as diabetes, depression, liver cirrhosis, cardiovascular disease, and metabolic disorders — and also have a generally lower mortality risk..

Consistency must be maintained every day, including weekends. So if you go to bed at 11 p.m. from Monday to Friday but at 2 a.m. on weekends, you're not doing your body any favors and would be considered an “irregular sleeper”.

Shift Bedtime by No More Than 30 Minutes

Bedtime should always fall within your personal “time zone” — give or take 30 minutes. If you usually fall asleep at 11 p.m., your personal sleep-time can vary from 10:30 p.m. toa 11:30 p.m. Based on the research, experts recommend finding and sticking to a regular sleep rhythm that fits your personal chronotype. The data clearly shows that a routine beginning before midnight is more beneficial than one starting significantly later. Falling asleep after 12:30 a.m. significantly increases the risk of many diseases.

Those who sleep regularly should also wake up regularly, keeping sleep duration consistent — even on weekends. For many, off days are the time to “catch up” on missed sleep. However, research shows that you can only make up for lost sleep within a 24-hour window — meaning a sleep deficit from Thursday can’t be made up on Saturday.

Power Nap Instead of Sleeping In on Weekends

If you want a little extra rest on your days off, it’s better to plan a midday nap. A maximum 20‑minute power nap is recommended. Longer naps can lead into the next sleep phase, and waking after 30 or 40 minutes can leave you feeling more tired than before. A 20‑minute nap, on the other hand, boosts recovery, lifts mood, and even reduces the risk of cardiovascular disease.

If power naps aren’t your thing, you can occasionally plan a long siesta — a full 90‑minute sleep cycle — but before 3 p.m., otherwise your regular bedtime in the evening may be disrupted.