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Sleep-wake preferences in rural Brazilian population could inform related health outcomes
Artificial lighting appears to be pushing people away from a natural sleep-wake cycle, resulting in sleep loss and potentially an array of related health consequences, including obesity and diabetes, according to research published in Scientific Reports.
Using data from a family-based cohort study in Baependi, a small rural town in southeastern Brazil where residents follow a schedule similar to preindustrial times, researchers found distinct diurnal preferences that could serve as foundation for future research.
“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,” Malcolm von Schantz, PhD, of the University of Surrey, said in a news release. “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.”
Researchers from the University of Surrey and the University of São Paulo administered the Morningness-Eveningness Questionnaire (MEQ) among 825 individuals aged 18 to 89 years from 112 different families; the questionnaire is the most frequently used to assess chronotype.
The average MEQ score was 63.5 ± 11.2, and a linear increase was seen with age (P < .0001).
Morningness was higher (P < .0001) among rural residents (70.2 ± 9.8) than municipal residents (62.6 ± 11.1). Morningness was also higher (P = .025) in men (64.6 ± 10.9) than women (62.8 ± 11.2).
For preferred wake and sleep times, municipal residents reported 7:15 a.m. and 10:20 p.m. compared with 6:30 a.m. and 9:20 p.m. among rural residents.
“When we asked the same question in London, the average answers were 8:30 a.m. and 11:15 p.m.,” von Schantz said in the release.
“The people of Baependi, particularly those in the countryside, maintain a much stronger link with the solar rhythm, largely because many of them work outdoors. Midnight really represents the middle of the dark phase, and yet many of us in the industrialized world are not even in bed by then.”
With more data emerging on health outcomes of the population from research at University of São Paulo, investigators are hopeful to uncover relationships between sleep and various conditions.
“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,” von Schantz said. – by Allegra Tiver
Disclosure: The researchers report no relevant financial disclosures.