*Corresponding author e-mail: mctq@ufpr.br Introduction: In the beginning of Brazilian daylight saving time (DST), the social clock is advanced by one hour, often inducing a circadian rhythms adjustment. The objective of this study is to compare sleep-patterns and mood before and after DST transition and identify. Methods: Fifty four volunteers, freshmen undergraduate students, participated in the pilot study. They answered the Horne- Östberg questionnaire to assess chronotype and kept sleep logs during two consecutive weeks, one before and one after the beginning of DST to record sleep-wake patterns, sleepiness and mood. Sleepiness was assessed every day at 8am, 12pm, 6pm and 8pm by means of a visual analogue scale (VAS). Mood variables (anxiety, fatigue and anger) were obtained by the same means. Data before and after DST transition were compared using t-test. Results: The mean score of chronotype was 47.05±12.92. Subjects showed later sleep times (before= 11:36pm / after=12:l4am, p <0.01) and wake up times (before=07:12am / after=08:13am, p <0.01). Subjects also showed an increase of sleepiness at 8am (p<0,01). Differences on mood variables were not found. Conclusion: The results suggest that there is no adjustment of sleep-wake times in the first week after DST beginning. Publication History Article published online: 16 June 2026 © 2009. Brazilian Sleep Academy. This is an open access article published by Thieme under the terms of the Creative Commons Attribution-NonDerivative-NonCommercial License, permitting copying and reproduction so long as the original work is given appropriate credit. Contents may not be used for commercial purposes, or adapted, remixed, transformed or built upon. (https://creativecommons.org/licenses/by-nc-nd/4.0/) Thieme Revinter Publicações Ltda. Rua Rego Freitas, 175, loja 1, República, São Paulo, SP, CEP 01220-010, Brazil
Quintilham et al. (Thu,) studied this question.