When it comes to sleep, is eight hours really the magic number?
While adequate rest is undoubtedly an important component of human health, how much sleep we need isn’t necessarily the same for everyone.
A new review from Brain Medicine challenges the notion that all adults require eight hours of sleep per night to be healthy.
“Human sleep patterns in pre-industrial societies exhibit substantial flexibility, suggesting that contemporary norms of consolidated nocturnal sleep are not evolutionarily fixed,” according to the authors.
In other words, healthy sleep patterns can vary from person to person — and history supports this idea.
Ancestral sleep patterns vs. modern shut-eye
Humans, of course, have always required sleep.
Long before the implementation of the 40-hour workweek, the invention of alarm clocks and the use of cell phones, people relied on a more natural sleep cycle — one that often didn’t amount to eight hours a night.
Per The Conversation, researchers have studied hunter-gatherer communities — whose lifestyles share more similarities with those of our ancestors and who have limited or no exposure to artificial light — to better understand natural sleep duration in humans.
The publication then cites a study published in Current Biology, which found that people in Tanzania, Namibia and Bolivia slept for between 5.7 and 7.1 hours a night.
“The short nights also seemed to be enough: people did not make up for them with long daytime naps. Without an alarm clock, they tended to wake close to dawn, regardless of the day of the week,” the outlet states.
Additionally, an analysis published by the Royal Society Publishing estimates that people slept an average of 6.4 hours per night in pre-industrial societies. The journal also acknowledges that modern sleep patterns “are delayed relative to the natural light-dark cycle,” per The Conversation.
“Most of us do not wake naturally before dawn. Many of us have short sleep during the working week and longer catch-up sleep on work-free days,” the outlet states.
Artificial light — from lamps, computers and smartphones — is considered a major culprit behind this delayed pattern.
Citing an article from Nature, The Conversation points out that artificial light “changes our sleep habits and delays our body clock, which controls the timing of sleep and wakefulness.”
Individual sleep needs
Individual factors — such as health status and biological sex — also play a role in determining a person’s sleep requirements.
According to The Conversation, “If we define optimal sleep as the amount linked to the best health, many large studies suggest the sweet spot may be less than eight hours.”
Another study published in Nature used brain and body scans, along with molecular measures, to examine how sleep relates to the aging of different organs. It estimated that the ideal amount of sleep is between 6.4 and 7.8 hours, depending on the individual’s sex and the specific organ observed.
How much sleep should I be getting?
Based on the above information, it’s safe to say that eight hours isn’t necessarily the golden rule of sleep — though that doesn’t mean eight hours is too much or too little for you.
Eight hours may work well for your spouse, but it may leave you still feeling tired. Nine hours may suit you best, but could feel like overkill for your friend.
As The Conversation states, “The eight-hour rule is clearly too simple. People need different amounts of sleep, and when we sleep matters too.”
According to the National Sleep Foundation, adults between the ages of 26 and 64 should get between seven and nine hours of sleep per day, though some adults may require between six and 10 hours.
Therefore, the sleep “sweet spot” varies from person to person, and eight hours certainly isn’t a concrete answer.
