Self-reported discomfort associated with Daylight Saving Time in Brazilian tropical and subtropical zones

AbstractBackground: Daylight Saving Time (DST) annually moves clocks 1 hour forward, when daytime is longer than night. Previous studies from medium and high latitude locations have pointed to a disruptive effect of DST on human circadian rhythms. Since Brazil is an equatorial country implementing DST, a different relationship between photic and social synchronisers may interfere with DST effects.Aim: To explore the prevalence and duration of self-reported discomfort related to DST among Brazilian residents (latitude 12–33° S, longditude 39–57° W). It was hypothesised that an elevated prevalence of self-reported discomfort would be found in Brazil, due to the pronounced uncoupling between social and geophysical synchronisers.Subjects and methods: In total, 12 467 volunteers completed a web-based, Brazilian version of Horne-Ostberg Morningness-Eveningness Questionnaire, provided demographic information, and answered questions related to DST complaints (discomfort, duration of discomfort).Results: Of the to...