title: Geographic latitude and sleep duration: A population-based survey from the Tropic of Capricorn to the Antarctic Circle.
abstract: The impact of latitude on sleep duration remains virtually unexplored, even though latitude exerts profound influences on daylight duration. Using Chile as a one-country model, we explored on the potential associations between sleep duration and latitude. Based on the 2nd Chilean Health Survey, we identified reported sleep data during spring of people living from north to south in Chilean cities, located between 18°29'S to 53°18'S (4329 km distance at same longitude). A total of n = 2493 participants were included (mean age 45.3 ± 18.4 years, 41.8% males). Mean sleep duration on workdays and weekends was 7.42 ± 1.71 h, and 7.91 ± 2.13 h, respectively, ranging from 7.91 ± 1.92 h in the north to 8.33 ± 1.89 h in the south, such that more northern latitudes (i.e., 18°29'S to 39°50'S) slept less compared to more southern latitudes (i.e., 51°43'S-53°18'), even after controlling for age, gender, and socioeconomic status. In the logistic regression models, men residing at northern latitudes exhibited an odds ratio of 3.348 [95% CI: 1.905-5.882; p < 0.0001] for having shorter sleep on weekends than their southern counterparts. Latitude appears to strongly affect reported sleep patterns, leading to longer sleep duration with increasing latitude, particularly in men during weekends. Whether environmental factors such as photoperiod are causally involved in theses associations needs to be elucidated in future studies.
authors.affiliation: a Department of Pediatric Cardiology and Pulmonology , Division of Pediatrics, School of Medicine, Pontificia Universidad Católica de Chile , Santiago , Chile.|b Sleep Medicine Center, Department of Neurology , School of Medicine, Pontificia Universidad Católica de Chile , Santiago , Chile.
authors.forename: Pablo E
authors.initials: PE
authors.lastname: Brockmann
authors.affiliation: c Sections of Pediatric Sleep Medicine and Pulmonology, Department of Pediatrics, Pritzker School of Medicine , Biological Sciences Division, The University of Chicago , Chicago , IL , USA.
authors.forename: David
authors.initials: D
authors.lastname: Gozal
authors.affiliation: d Department of Public Health, School of Medicine , Pontificia Universidad Católica de Chile , Santiago , Chile.
authors.forename: Luis
authors.initials: L
authors.lastname: Villarroel
authors.affiliation: e School of Medicine, Pontificia Universidad Católica de Chile , Santiago , Chile.
authors.forename: Felipe
authors.initials: F
authors.lastname: Damiani
authors.affiliation: e School of Medicine, Pontificia Universidad Católica de Chile , Santiago , Chile.
authors.forename: Felipe
authors.initials: F
authors.lastname: Nuñez
authors.affiliation: f Centre for Chronobiology, Psychiatric Hospital of the University of Basel , Basel , Switzerland.
authors.forename: Christian
authors.initials: C
authors.lastname: Cajochen
mesh_terms: D000328:Adult; D000864:Antarctic Regions; D002940:Circadian Rhythm / Q000502:physiology*; D004777:Environment; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D017440:Photoperiod; D012621:Seasons; D012890:Sleep / Q000502:physiology*; D011795:Surveys and Questionnaires; D013997:Time Factors
keywords: Circadian; geography; insomnia; sleep hours; sleepiness