Sleep and light exposure across different levels of urbanisation in Brazilian communities

Abstract

Quilombos are settlements originally founded by Africans and African descendants (Quilombolas) in remote parts of Brazil to escape slavery. Due to individual histories, Quilombos nowadays exhibit different states of industrialisation, making them ideal for studying the influence of electrification on daily behaviour. In a comparative approach, we aimed to understand whether and how human sleep changes with the introduction of artificial light. We investigated daily rest-activity-rhythms and sleep-patterns in the Quilombolas’ by both wrist actimetry and the Munich ChronoType Questionnaire (MCTQ; the results of these two instruments correlated highly). Seven communities (MCTQ: N = 213/actimetry: N = 125) were compared in this study. Light exposure, phase of activity, sleep timing and duration differ across communities with various levels of urbanisation and histories of access to electricity. People living without electricity and those, who acquired it only very recently on average sleep earlier than those in more urbanised communities (mid-sleep about 1 hour earlier); sleep duration tends to be longer. Our results and those of others show that use of electricity and modern lifestyles have changed sleep behaviour. To understand the consequences of these changes for health, further studies are warranted.

Clocks in the Wild: Entrainment to Natural Light

“…variance through seasonal and latitudinal variations are difficult to obtain amidst these internal heterogeneities, in addition to confounding cultural influences amongst studies including societies of different lifestyles (Pilz et al, 2018). We expect that finer details of chronotype diversity can be predicted in defined subpopulations of age and gender when more precise physiological mechanisms of chronotypes are known.…”

Seasonal synchronization of sleep timing in industrial and pre-industrial societies: the regulating role of Daylight Saving Time

“…Finally, Pilz et al [10] investigated sleep patterns in the Quilombolas along a series of seven communities in Southern Brazil (states of Paraná, Rio Grande do Sul and São Paulo) with different degrees of urbanization. The study was conducted from March 2012 to March 2017 and Table II collects sleep timing presented in Table S2 (winter, actimetry data) of the cited reference, which reports standard deviations in the range from 30 min to 120 min.…”

“…Four of the five remaining studies report winterautumn data, and only Moreno et al [7] reported data in spring-summer only. Except for the Quilombolas [10] -who live at 30 • where the variation of sunrise times climbs close to two hours (see Table I)-data will be used indistinctly in winter and summer analysis.…”

“…Three of these studies analyzed hunter-gatherer, horticulturalist, pre-industrial societies [4][5][6] and reported similar or shorter sleep durations compared with industrial societies. In contrast another group of four studies reported data on homogeneous pre-industrial communities with and without access to electricity [7][8][9][10] and reported later sleep onset times and shorter sleep duration with increasing urbanization. This manuscript will not address the impact of artificial light on sleep duration.…”

Eating Behavior (Duration, Content, and Timing) Among Workers Living under Different Levels of Urbanization

“…The urbanization process, as well as the use of electricity and the technologies derived from this, allow extended wakefulness and provide the opportunity to carry out activities after sunset [1][2][3]. Studies conducted in communities with and without access to electricity have shown that electric light can lead to delayed sleep onset and, consequently, to reduced sleep duration [4][5][6]. Moreno et al [5] also observed that rubber tappers from the Amazon forest with access to electricity had delayed 2.…”