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Natural Sleep and Its Seasonal Variations in Three Pre-industrial Societies

2015; Elsevier BV; Volume: 25; Issue: 21 Linguagem: Inglês

10.1016/j.cub.2015.09.046

1879-0445

Gandhi Yetish, Hillard Kaplan, Michael Gurven, Brian M. Wood, Herman Pontzer, Paul R. Manger, Charles L. Wilson, R. L. McGregor, Jerome M. Siegel,

Obstructive Sleep Apnea Research

How did humans sleep before the modern era? Because the tools to measure sleep under natural conditions were developed long after the invention of the electric devices suspected of delaying and reducing sleep, we investigated sleep in three preindustrial societies [1Marlowe F. The Hadza Hunter-Gatherers of Tanzania. University of California Press, 2010Google Scholar, 2Schuster S.C. Miller W. Ratan A. Tomsho L.P. Giardine B. Kasson L.R. Harris R.S. Petersen D.C. Zhao F. Qi J. et al.Complete Khoisan and Bantu genomes from southern Africa.Nature. 2010; 463: 943-947Crossref PubMed Scopus (298) Google Scholar, 3Vasunilashorn S. Crimmins E.M. Kim J.K. Winking J. Gurven M. Kaplan H. Finch C.E. Blood lipids, infection, and inflammatory markers in the Tsimane of Bolivia.Am. J. Hum. Biol. 2010; 22: 731-740Crossref PubMed Scopus (69) Google Scholar]. We find that all three show similar sleep organization, suggesting that they express core human sleep patterns, most likely characteristic of pre-modern era Homo sapiens. Sleep periods, the times from onset to offset, averaged 6.9–8.5 hr, with sleep durations of 5.7–7.1 hr, amounts near the low end of those industrial societies [4Blackwell T. Ancoli-Israel S. Redline S. Stone K.L. Osteoporotic Fractures in Men (MrOS) Study GroupFactors that may influence the classification of sleep-wake by wrist actigraphy: the MrOS Sleep Study.J. Clin. Sleep Med. 2011; 7: 357-367PubMed Google Scholar, 5Heeren M. Sojref F. Schuppner R. Worthmann H. Pflugrad H. Tryc A.B. Pasedag T. Weissenborn K. Active at night, sleepy all day--sleep disturbances in patients with hepatitis C virus infection.J. Hepatol. 2014; 60: 732-740Abstract Full Text Full Text PDF PubMed Scopus (34) Google Scholar, 6Natale V. Léger D. Martoni M. Bayon V. Erbacci A. The role of actigraphy in the assessment of primary insomnia: a retrospective study.Sleep Med. 2014; 15: 111-115Abstract Full Text Full Text PDF PubMed Scopus (73) Google Scholar, 7Robillard R. Naismith S.L. Smith K.L. Rogers N.L. White D. Terpening Z. Ip T.K. Hermens D.F. Whitwell B. Scott E.M. Hickie I.B. Sleep-wake cycle in young and older persons with a lifetime history of mood disorders.PLoS ONE. 2014; 9: e87763Crossref PubMed Scopus (49) Google Scholar]. There was a difference of nearly 1 hr between summer and winter sleep. Daily variation in sleep duration was strongly linked to time of onset, rather than offset. None of these groups began sleep near sunset, onset occurring, on average, 3.3 hr after sunset. Awakening was usually before sunrise. The sleep period consistently occurred during the nighttime period of falling environmental temperature, was not interrupted by extended periods of waking, and terminated, with vasoconstriction, near the nadir of daily ambient temperature. The daily cycle of temperature change, largely eliminated from modern sleep environments, may be a potent natural regulator of sleep. Light exposure was maximal in the morning and greatly decreased at noon, indicating that all three groups seek shade at midday and that light activation of the suprachiasmatic nucleus is maximal in the morning. Napping occurred on <7% of days in winter and <22% of days in summer. Mimicking aspects of the natural environment might be effective in treating certain modern sleep disorders.