Brazilian residents retained natural sleep cycles we lost after Industrial Revolution

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Brazilian residents retained natural sleep cycles we lost after Industrial Revolution

Posted by sciencetech-blog on Wednesday, March 18, 2015 Label:

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Our ancestors typically rose with the sun and went to sleep when it set, but modern life and artificial lighting has pushed this routine out of sync.

However, researchers have discovered a rural community in Brazil that still follows the natural sleep cycles of the past - despite having access to the same technology as its urban neighbours.

And they now plan to study this group to learn more about how our move away from the natural rhythm could be damaging our health.

Researchers have discovered a rural community in Brazil that follows the 'natural sleep cycles' (stock image) of our ancestors who rose with the sun, and typically went to bed when it set. The experts now plan to study this group to learn more about how our move away from the natural rhythm could be damaging our health

The community was discovered in the small town of Baependi in south-eastern Brazil in the state of Minais Gerais.

Researchers from the University of Surrey and the University of São Paulo studied the population and asked them questions about their sleep habits and patterns.

'In big cities, the availability of cheap electricity has brought us both artificial lighting and a multitude of other electronic devices that compete with us going to sleep at night,' said lead author Dr Malcolm von Schantz from the University of Surrey.

'As a result, most of us go to bed much later than our ancestors did, and, many of us are sleeping less.

'Even though the people in Baependi have access to electricity and television, their daily rhythms are much closer to those of previous generations.

'Studying this population is like being able to look back at past generations through a pair of binoculars and provide an insight into the benefit this natural pattern may be having on their health.'

OUR ANCESTORS SLEPT TWICE A NIGHT

Historian Roger Ekirch of Virginia Tech recently revealed an 'overwhelming amount of historical evidence' that suggested we used to sleep in stages.

He found more than 500 references about ancestors sleeping in two shorter periods throughout the night.

The total sleep would occur in a 12-hour period that began with up to four hours sleep, an 'awake period' of four hours and then ended with a second four-hour sleep.

These days it is widely accepted human sleep patterns are governed by the 'circadian rhythm'.

This is the 24-hour cycle of being awake and then, when it becomes dark, resting.

'However, built into this 24-hour pattern is a series of shorter cycles of about 90 minutes - called the "ultradian rhythm",' added Dr Nerina Ramlakhan, author of Tired But Wired: How To Overcome Your Sleep Problems.

This explains smaller peaks and troughs of energy throughout the day.

Dr Ramlakhan believes this ultradian rhythm is a throwback to our hunter-gatherer years.

And while we tend to pay much more attention to the 24-hour cycle than the 90-minute one, Dr Ramlakhan believes the body works best when we move with these natural ultradian rhythms, building in pauses, stopping and resting, so continually renewing our energy.

The community was discovered in Baependi (marked) in south-eastern Brazil. Residents were asked when they would prefer to wake up and go to bed, and the average answers from the town dwellers were 07.15am and 22.20pm. Whereas people in the countryside preferred to rise at 06.30am and go to bed at 21.20pm

In particular, the residents were asked when they would prefer to wake up and go to bed if they were completely free to plan their day.

The average answers from town residents were 07.15 and 22.20, whereas people in the surrounding countryside preferred to rise at 06.30am and go to bed at 21.20.

The researchers believe the difference is due to town residents following much less of a natural sleep/wake cycle because of the influence of artificial lighting.

'When we asked the same question in London, the average answers were 08.30am and 23.15pm,' continued Dr von Schantz.

The paper explained that people in Baependi maintain a stronger link with the so-called solar rhythm because they predominantly work outdoors. They therefore have similar patterns as pre-industrial ancestors. Town residents follow less of a natural sleep/wake cycle because of the influence of artificial lighting (stock image)

The paper explained that the people of Baependi, especially those in the countryside, maintain a much stronger link with the so-called solar rhythm.

This is because they predominantly work outdoors and therefore have similar patterns as our pre-industrial ancestors.

Solar time uses the mid-points of the light and dark 'periods' - notably midnight and noon - as timing references.

In circadian rhythms, sunrise start this clock on its 24-hour run, but this continues regardless of a shift in when the sun sets meaning the mid-points vary.

'Midnight really represents the middle of the dark phase, and yet many of us in the industrialised world are not even in bed by then,' continued Dr von Schantz.

'Our colleagues at the University of São Paulo have studied this population, so there is a lot of data emerging about the health outcomes of the same population.

'We are optimistic that this project will teach us to what extent cardiovascular health, obesity, diabetes, and mental health problems may be associated with our move away from the natural day/night cycle, and the associated sleep loss.'

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