What We Can Learn About Sleep Schedules From A Rural Town In Brazil

03/20/2015 01:17 pm ET | Updated Mar 20, 2015
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How early would you wake up every morning if you didn't have a modern office job?

If your work involves more computer screens than plots of land, chances are you woke up earlier than you wanted to, and if you had a choice in the matter, you would love to wake up a couple of hours later than you normally do. But if you live in the country, where your day’s rhythms are regulated by the sun and your work is manual labor that keeps you outside, chances are that you’re just fine with waking up early.

That's just one of the discoveries from a recent study of the rural Brazilian town of Baependi. Malcolm von Schantz, a sleep and circadian rhythms researcher at the University of Surrey in the U.K., surveyed 825 of the town's residents and revealed that they were much more likely to be morning people -- people that feel best and most alert in the mornings -- than urban people in major metropolises like Sao Paulo or London.

His research, published online on March 19 in the journal Scientific Reports, states that people living in the rural zone of the town prefer rise and bed times one hour earlier than in those big metropolises like Sao Paolo or London. As for the people who live in even more rural zones on the outskirts of Baependi, their wake and sleep time preferences were two hours earlier than metropolis-dwellers.

Von Schantz isn’t yet sure why that may be, although he suspects that it may have to do the community’s main industries: agriculture and open-cast mining, which is mining in a large, open pit. The two manual labor jobs expose residents to a lot more natural sunlight than the average urban dweller, he explains in his study:

The most obvious and likely strongest determinant of this difference [between urban and rural] is differential exposure to natural light during the day (particularly during the advancing window of the phase response curve) and artificial light (from indoor or outdoor sources) during the night (particularly during the delaying window of the phase response curve). Other factors that could potentially contribute to the observed difference include a greater prevalence of hard physical labour in rural than in metropolitan areas, and the possibility that a rural individual with limited formal education (or even none at all), and limited experience of the outside world, may be unable to think abstractly about a life of leisure when answering questions such as preferred rise- and bedtime if they were completely free to plan their day.

Von Schantz used a questionnaire based on a 1976 test called the Morningness-Eveningness Questionnaire to survey people about their circadian rhythm types. It contains such questions as “How easy do you find it to get up in the morning?" or “How alert do you feel during the first half hour after you wake up in the morning?," and then scores you on a scale between zero to 100 to determine whether you’re naturally a Morning Person or a Night Owl. The test is a significant and often-used resource for sleep scientists because it has been validated against circadian rhythms as measured by oral temperature, but is a more convenient way of assessing morningness or eveningness.

If you want to find out whether you’re a morning person or a night owl, the Morningness-Eveningness Questionnaire is available for free online.

On one of the survey questions -- “Approximately what time would you get up if you were entirely free to plan your day?” -- many of the most rural respondents wanted to choose a time earlier than 5 a.m., even though the questionnaire choices only allowed for time slots between 5 a.m. and noon, according to von Schantz. The same went for their preferred bedtime: The questionnaire only allows you to choose between the hours of 8 p.m. or 3 a.m., and the most rural residents preferred bedtimes before then.

Interestingly enough, just because Baependi residents tended to prefer pre-industrial wake and sleep times, it didn’t mean they led completely pre-industrial lives. The community is generally traditional, cohesive and conservative, and migration was almost non-existent. But 93.9 percent of homes had a TV in it, while 19.1 percent had internet access. Just for reference, among the general population of Brazil, 60 percent of homes lack internet access.

Von Schantz compared his research to a small but compelling 2013 study of natural and artificial light, involving eight participants. They camped for one week in the Rocky Mountains of Colorado without their cell phones, flashlights and any other personal electronic device, and as they acclimated to the natural light, their internal circadian rhythms shifted about two hours earlier than their baseline wake and sleep times, which had been measured during their normal work and school schedules.

The natural sunlight and lack of artificial light also flattened out any differences in morningness or eveningness among the participants, and researchers observed that release of the hormone melatonin, which makes people feel sleepy in the evenings, more closely aligned with the sunset than it did when they were living their normal, artificially-lit life.

"What we find is that the people in this little town [Baependi] behave essentially like these campers, even though they do have electricity,” wrote Von Schantz to HuffPost. "It is a fascinating little town, with a traditional lifestyle; this may be a contributing factor. But I think the major answer is that, like [the] campers, they are exposing themselves to high levels of natural light at the right time of day."

Von Schantz and colleagues have been following Baependi residents and collecting health data for more than nine years and he hopes to analyze their morning schedules further to assess any link to cardiovascular, metabolic and mental health outcomes. In the meantime, he argues that this initial look at Baependi residents raises interesting questions about urban bedtimes and their impact on our lives.

"I think it is important to remind ourselves that, with cheap and unlimited access to electricity, our bedtime has been creeping gradually later over recent decades,” von Schantz wrote. “There is very strong evidence that chronic sleep deprivation has multiple negative effects on our health -- this includes mortality in general, obesity, diabetes, cardiovascular disease, and also impaired vigilance and cognition."

Indeed, nearly 30 percent of U.S. adults reported an average of less than six hours of sleep a day from 2005 to 2007, while the recommended amount of hours for optimal health are between seven and nine hours.

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