Anthropologists, geneticists, and historians gathered data and discovered that eight hours of sleep is a false standard, revealing the factors that really affect sleep quality and why routine is more important than quantity.
According to scientists, humans are believed to need exactly eight hours of sleep, a figure repeated everywhere—in apps, doctors' recommendations, and educational materials for children. But a new, large-scale study, drawing on data from anthropology, history, and genetics, has shown that the eight-hour standard is more of a myth than a scientific fact.
Scientists studied the sleep patterns of three groups of hunter-gatherers—the Hadza in Tanzania, the San in Namibia, and the Tsimane in Bolivia—who live without electricity. They found that these groups sleep an average of 6.4 to 7.1 hours—no more, and sometimes even less, than modern city dwellers.
Interestingly, the idea of "eight hours of sleep" emerged in the 19th century, when the pattern of eight hours of work, eight hours of rest, and eight hours of sleep became established. However, no one at the time measured the actual number of hours of sleep. Even the earliest studies that have been cited focused mostly on children, not adults. It turns out that this pattern was invented, not discovered.
According to scientists, the main difference between sleep in the modern age and sleep in pre-industrial times lies in its pattern, not its duration. In traditional societies, people went to sleep shortly after sunset and woke with dawn, their sleep closely linked to natural light. In our society, however, light, screens, noise, and irregular sleep schedules delay sleep, disrupting its pattern and quality. Nevertheless, the total number of hours has not changed significantly.
Furthermore, the common belief that people slept in two phases—a "first sleep" and a "second sleep"—is debatable. Archival sources can be interpreted in multiple ways, and experiments conducted in complete darkness do not reflect the reality of life in the past, where fires and candles were lit in the evenings.
Genetics also casts doubt on the universality of eight hours of sleep. Some people, due to a mutation in the DEC2 gene, sleep only six hours and yet feel perfectly healthy. These individuals show no signs of sleep deprivation, and there's no need to interfere with their sleep schedule—it's not a disease, but a personality trait.
Researchers have found that the number of hours of sleep is not as important as the regularity and timing of sleep, and its relationship to natural light. The environment also plays a significant role; noise, light, temperature, and housing quality all affect sleep.
