Archive · 27 Aug 2026
Experts Say Eight Hours May Not Suit Every Adult
Many adults have heard that they must sleep exactly eight hours every night.
Experts now say that one number may not work for everyone.
Some studies found that people in certain pre-industrial societies slept fewer than eight hours.
Another study estimated that the best amount may be between 6.4 and 7.8 hours for different people.
When a person sleeps may matter as much as how long they sleep.
Going to bed and waking up at similar times can help the body’s natural clock.
Bright lights and night work can make that clock less regular.
Sleeping longer on weekends may help with short-term tiredness, but a steady schedule is considered better overall.
A review in Brain Medicine says the eight-hour sleep rule is overly simplistic for adults.
Research cited in the review found some pre-industrial populations slept 5.7 to 7.1 hours nightly.
A Nature study estimated an ideal sleep range of 6.4 to 7.8 hours, depending on sex and the organ examined.
Researchers say sleep timing and consistency matter alongside total hours.
Artificial light, urbanisation and night-shift work can disrupt natural sleep patterns and circadian rhythms.
- Who
- Researchers studying adult sleep and circadian rhythms.
- What
- A review argues that eight hours is not a universal sleep requirement and that duration, timing and consistency all matter.
- When
- The review was recently published; the cited studies examined sleep patterns in pre-industrial societies and modern adults.
- Where
- The review cites research involving populations in Tanzania, Namibia and Bolivia, as well as studies published in Brain Medicine, Current Biology and Nature.
- Why
- Modern lighting, urbanisation and night-shift work can disrupt natural light-dark cycles, while individual sleep needs vary.
- Review publication
- Brain Medicine
- Sleep range in cited populations
- 5.7 to 7.1 hours per night in studies of people in Tanzania, Namibia and Bolivia
- Pre-industrial average
- Royal Society Publishing estimated an average of 6.4 hours per night
- Estimated individual range
- A Nature study estimated 6.4 to 7.8 hours, depending on sex and the organ examined
- Key sleep factors
- Duration, timing and consistency
- Potential disruptors
- Artificial illumination, urbanisation and night-shift work
- Weekend catch-up sleep
- May reduce short-term exhaustion, but regular sleep throughout the week is presented as preferable