For decades, it was believed that adults should sleep exactly 8 hours a day. This idea dates back to the 19th century, when “8 hours of work, 8 hours of rest, 8 hours of sleep” became something of a standard. However, a new scientific review published in the journal Brain Medicine shows that the 8-hour rule is far from ideal for everyone.
To determine how long people naturally sleep, scientists studied tribes and communities without access to artificial lighting, including populations in Tanzania, Namibia, and Bolivia. They found that people living in pre-industrial conditions sleep an average of 5.7 to 7.1 hours. Notably, this amount of sleep appears to be sufficient for them: they do not nap during the day and wake naturally at dawn without an alarm clock.
Large-scale medical studies conducted in modern societies have also confirmed that the so-called “sweet spot” for health is less than 8 hours. By observing the aging processes of the brain and various organs of the body, researchers found that the optimal sleep duration ranges from 6.4 to 7.8 hours, depending on sex and the specific organ being studied. Scientists agree that both insufficient and excessive sleep are associated with poorer health, including heart disease, obesity, and cognitive decline.
Experts emphasize that sleep duration is highly individual and that there is no such thing as an “average person.” According to recommendations from the U.S. National Sleep Foundation, adults aged 26 to 64 should ideally get 7 to 9 hours of sleep, although for some people, 6 or even 10 hours may be perfectly normal. Therefore, a universal 8-hour rule does not accurately reflect reality.
In addition to duration, sleep timing is extremely important. Artificial light alters our biological clock, which is why most people can no longer wake naturally at dawn. At the same time, the pace of modern life often makes sleep schedules irregular, particularly among students and shift workers. According to the researchers, although maintaining a consistent sleep schedule is important, catching up on sleep lost during the workweek over the weekend is far better than remaining sleep-deprived altogether.
The scientists’ main advice is simple: there is no need to stress about getting exactly 8 hours of sleep. Simply sleep as much as your body needs, and do not worry if you occasionally fail to get a full night’s sleep.
