PSYCHOPHYSIOLOGICAL EFFECTS OF ELIMINATIN G DAYLIGHT SAVING TIME ON APOPULATION NEVER BEFORE EXPOSED TO SUCH A SCHEDULE

Daylight saving time (advancing one hour) was first introduced into fo ur states of Mexico in 1988, from March 3 to October 30. The objective of this study was to determine the effects of daylight saving time el imination (returning to standard time) on a population never before ex posed to such schedule. Nineteen workers (12 female, 7 male) kept a sl eep-wake diary for 26 days, 9 days before and 17 days after daylight s aving time elimination. Each worker answered a sleep disorders questio nnaire, the Zung Depressive Scale and the Morningness-eveningness Scal e at the beginning and at the end of the study. All workers delayed th eir waking time. Twelve persons delayed their time of falling asleep ( from 23:04 to 24:04 h daytime) and reduced their sleep duration (from 8:01 to 7:38 h) but had less tiredness when waking up. The remaining p ersons did not delay their time of falling asleep (from 23:19 to 23:40 h daytime) but reduced their sleep latency and their difficulties for falling asleep.These results support the hypothesis that daylight sav ing time elimination (delaying one hour) produces fewer problems on th e human circadian system, than daylight saving time introduction (adva ncing one hour).