Study of primitive tribes shows we're all still 'Paleo' sleepers
People in modern societies get about the same amount of sleep as those in pre-industrial communities in Africa and Latin America - who average a little less than 6.5 hours a night, and don't take naps - UCLA study finds
The trappings of modern life, such as television and the internet, as well as increased caffeine usage, are often blamed for shortening our sleep duration from “natural” levels and disrupting our circadian rhythms. But a new study that investigated sleep in three ancient groups of hunter-gatherers living in Africa and Bolivia shows these preindustrial societies don’t get any more sleep than we do.
These traditional people were found to sleep between 5.7 to 7.1 hours a night – on average, a little under 6.5 hours a night. They don’t take regular naps. And they go to sleep on average three hours after sunset and typically awaken before sunrise.
In other words, their sleep habits aren’t so different from ours, say the researchers in their study in the journal Current Biology published on October 15.
"The short sleep in these populations challenges the belief that sleep has been greatly reduced in the 'modern world,'" says Jerome Siegel of the University of California, Los Angeles. "This has important implications for the idea that we need to take sleeping pills because sleep has been reduced from its 'natural level' by the widespread use of electricity, TV, the Internet, and so on."
The US National Sleep Foundation recommends adults get seven to nine hours of sleep a night. Many Hongkongers fail to do so: the latest Health Department statistics from 2011 found that 35.5 per cent of adults slept fewer than seven hours a day on average. Only 6.4 per cent of the 2,000 adults polled got more than eight hours of sleep a night.
The purported reduction in sleep duration has been linked to obesity, mood disorders, and a host of other physical and mental illnesses thought to have increased recently.
But Siegel and his research team, based on their findings, suggest our modern sleeping durations could be a “core human sleep pattern”.
For the study, the researchers tracked around the clock a total of 94 individuals from the Hadza of northern Tanzania, the San of Namibia, and the Tsimane of Bolivia. The data collected represented 1,165 days in all.
In these societies, electricity and its associated lighting and entertainment distractions are absent, as are cooling and heating systems. Individuals are exposed, from birth, to sunlight and a continuous seasonal and daily variation in temperature.
There was a surprising similarity across the three groups. "Despite varying genetics, histories, and environments, we find that all three groups show a similar sleep organisation, suggesting that they express core human sleep patterns, probably characteristic of pre-modern-era Homo sapiens," Siegel says.
The hunter-gatherers’ sleep is largely regulated by the natural environment – natural light and ambient temperature. They sleep an hour more in the winter than in the summer. They go to sleep as the temperature falls and sleep through the coldest part of the night.
There is one important way in which hunter-gatherers aren't like us: very few of them suffer from chronic insomnia. Five per cent said they sometimes had sleep onset problems and nine per cent sometimes had sleep maintenance problems. Less than a third of these participants said they had these problems more than once a year.
In industrial societies, it's been reported that 10 to 30 per cent of people have chronic insomnia.
"Mimicking aspects of the natural environment experienced by these groups might be effective in treating certain modern sleep disorders, particularly insomnia," Siegel says.