Sleep/wake synchronization across latitude

Abstract

Analysis of time use surveys in seventeen European countries and two American countries suggest that the winter sunrise --the latest sunrise year round-- is a synchronizer for the sleep/wake cycle in standard population below 54{degrees} latitude, in competition with the noon synchronizer.\n\nWhen comparing industrialized data to data from hunter/gatherer, pre-industrial, Tropical societies only the late event survives as a synchronizer below 54{degrees} latitude. People rise immediately before sunrise --winter sunrise in industrialized mid-latitude societies-- and abhor morning darkness. Synchronization propagates through the sleep/wake cycle so that people go to bed with increasing distance to sunset in winter as latitude increases in a scenario dominated by artificial light. This suggests a leading role of the homeostatic sleep pressure in understanding sleep/wake cycle at social level.\n\nWARNINGThis pre-print has been largely upgraded and restyled in \"Sleep timing in industrial and pre-industrial societies sync to the light/dark cycle\" (https://doi.org/10.1101/392035). In this new pre-print data coming from the Harmonsized European Time Use Surveys (HETUS) and referred to the \"sleep/wake and other personal care\" cycle were not analyzed. Instead two new pre-industrial data are included.\n\nTherefore this old pre-print you are about to read remains as a source for these data (see Figure 3 and Table III, Table VII to IX) and a source of information in the range of latitude above 54{degrees}.\n\nO_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=124 SRC=\"FIGDIR/small/378737_fig3.gif\" ALT=\"Figure 3\">\nView larger version (29K):\norg.highwire.dtl.DTLVardef@a725a2org.highwire.dtl.DTLVardef@197cdcaorg.highwire.dtl.DTLVardef@1478997org.highwire.dtl.DTLVardef@19a236b_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOFigure 3.C_FLOATNO Timemarks extracted \"sleep and other personal care\" cycle against shortest photoperiod (right axis) or latitude (left axis). Bold circles show data from NTUS; open circles, data from HETUS. Lines and background colors highlight the cycle of light and dark. Lightest background is the region of permanent photoperiod; darkest background is the region of permanent dark; intermediate background shows the region that swings from light to dark as seasons go by. Blue solid lines show winter and summer terminator (z = -0.83{degrees}). Dotted lines the civil (z = -6{degrees}) and nautical (z = -12{degrees}) twilight lines in winter (dawn) and summer (dusk). Vertical solid lines highlight distance to noon. Slanted dash-dotted lines highlight distance to late event (winter sunrise and summer sunset). Summer lines have been delayed for one hour to accommodate daylight saving time. Geographical data are listed in Table I; timemarks appear in Table III.\n\nC_FIG O_TBL View this table:\norg.highwire.dtl.DTLVardef@8b4bc0org.highwire.dtl.DTLVardef@11a4533org.highwire.dtl.DTLVardef@1b52a4corg.highwire.dtl.DTLVardef@ec14aaorg.highwire.dtl.DTLVardef@140ddca_HPS_FORMAT_FIGEXP M_TBL O_FLOATNOTable III.C_FLOATNO O_TABLECAPTIONTimemarks obtained from \"sleep and other personal care\" cycle in NTUS (starred) and HETUS (non-starred) subsets. Size refers to the number of respondents of each survey. Timemarks are all expressed as a distance to solar noon in decimal hours. They list winter time values; one hour must be subtracted during summer time. Winter solar elevation angle at risetime zw and summer solar elevation angle at bedtimes zs are also provided. They show the lowest and largest possible values year round, either case the worst case scenario for rising or sleep onset. Distance computes the difference from bedtimes to next risetime. Values are displayed in Figure 1 (right) and 3.\n\nC_TABLECAPTION C_TBL O_TBL View this table:\norg.highwire.dtl.DTLVardef@1a12065org.highwire.dtl.DTLVardef@155f6e8org.highwire.dtl.DTLVardef@c539a1org.highwire.dtl.DTLVardef@4a84b4org.highwire.dtl.DTLVardef@4e7dfd_HPS_FORMAT_FIGEXP M_TBL O_FLOATNOTable VII.C_FLOATNO O_TABLECAPTIONMultiple linear regression analysis for \"sleep and other personal care\" timemarks. Each analysis takes the winter photoperiod as the predictor {xi}and the response {yi} is distance to noon. Probabilistic values and Pearsons coefficient are also given for distance to late event and distance to early event. They are obtained by testing {yi {mp}xi} against {xi}. Left column display analysis for all available data. In the right column HETUS duplicates were removed. Predictor and responses are displayed in Figure 3.\n\nC_TABLECAPTION C_TBL O_TBL View this table:\norg.highwire.dtl.DTLVardef@1319d69org.highwire.dtl.DTLVardef@559394org.highwire.dtl.DTLVardef@4bf984org.highwire.dtl.DTLVardef@1ea7c8dorg.highwire.dtl.DTLVardef@19729a9_HPS_FORMAT_FIGEXP M_TBL O_FLOATNOTable IX.C_FLOATNO O_TABLECAPTIONMultiple linear regression analysis for \"sleep and other personal care\" timemarks above 54{degrees}. Each analysis takes the winter photoperiod as the predictor {xi} and the response {yi} is distance to noon. Probabilistic values and Pearsons coefficient are also given for distance to late event and distance to early event. They are obtained by testing {yi {mp} xi} against {xi}. Predictor and responses are displayed in Figure 3\n\nC_TABLECAPTION C_TBL