Seasonal synchronization of sleep timing in industrial and pre-industrial societies
Martín Olalla, José María
- Published
- 2019-05-01
- Publisher
- Nature Research
- Language
- en
Abstract
Artificial light has reshaped human sleep/wake cycle in industrial societies and raised concern on the misalignment of this cycle relative to the light and dark cycle. This manuscript contrasts sleep timing in extratropical, industrial societies (data from eight national time use surveys in countries with Daylight Saving Time —DST— regulations) and Subtropical, pre-industrial societies with and without access to artificial light (data from nine locations coming from seven previous reports) against the cycle of light and dark. Within the two process model of sleep, results show sleep onset and sleep offset keep bound to each other by the homeostatic process. In winter, the photoreceptive process aligns the phase of the sleep/wake cycle to sunrise. As a result the phase increasingly lags with increasing latitude up to a delay of 120min at 55° latitude. In summer, the homeostatic process still binds sleep onset to speep offset but DST rules in industrialized societies reduce the lag by one third to 40min at 55° latitude. Sleep timing is then stationary with latitude. The phase of the sleep/wake cycle is then governed by natural trends and no clues of misalignment are revealed.
Full text
Supplementary material to: “Seasonal synchronization of sleep timing in industrial and pre-industrial societies” Jos´ e Mar´ıa Mart´ın-Olalla1 1 Universidad de Sevilla, Facultad de F ´ ısica. Departamento de F ´ ısica de la Materia Condensada. ES41080 Seville, Spain *email: [email protected]; twitter: @MartinOlalla JM ABSTRACT 1
Figure S1. Locations of the societies whose sleep timing is analyzed in this manuscript on an azimuthal projection centered at λ0=18◦80west of UTC prime meridian and 52◦latitude. The picture shows the Earth on a unique hemisphere from Equator (bottom) to the Pole (top). Solid symbols display societies with access to electricity. Open symbols display societies without access to electricity. Crosses display pairs of pre-industrial societies with and without access to electricity. Rounded symbols refer to societies physically in the Northern Hemisphere. Rest of symbols locate societies physically in the Southern Hemisphere. Circles of latitude in heavy dash-dotted lines are the Equator, the Tropic (at φ=ε) and the Polar Circle (at φ=90◦−ε ). Circles of latitude in light dashed lines run values of the shortest photoperiod Dw , increasing in steps of 1 h ; the circle nearest to the Polar Circle is Dw=5h. The picture separates light and dark in the winter day at noon over the meridian λ0. Continental and lake polygons were taken from http://www.naturalearthdata.com/. 2/2
