TY - JOUR T1 - The human circadian clock's seasonal adjustment is disrupted by daylight saving time. AU - Kantermann,Thomas, AU - Juda,Myriam, AU - Merrow,Martha, AU - Roenneberg,Till, Y1 - 2007/10/25/ PY - 2007/09/17/received PY - 2007/10/07/revised PY - 2007/10/09/accepted PY - 2007/10/30/pubmed PY - 2008/2/21/medline PY - 2007/10/30/entrez SP - 1996 EP - 2000 JF - Current biology : CB JO - Curr Biol VL - 17 IS - 22 N2 - A quarter of the world's population is subjected to a 1 hr time change twice a year (daylight saving time, DST). This reflects a change in social clocks, not environmental ones (e.g., dawn). The impact of DST is poorly understood. Circadian clocks use daylight to synchronize (entrain) to the organism's environment. Entrainment is so exact that humans adjust to the east-west progression of dawn within a given time zone. In a large survey (n = 55,000), we show that the timing of sleep on free days follows the seasonal progression of dawn under standard time, but not under DST. In a second study, we analyzed the timing of sleep and activity for 8 weeks around each DST transition in 50 subjects who were chronotyped (analyzed for their individual phase of entrainment). Both parameters readily adjust to the release from DST in autumn but the timing of activity does not adjust to the DST imposition in spring, especially in late chronotypes. Our data indicate that the human circadian system does not adjust to DST and that its seasonal adaptation to the changing photoperiods is disrupted by the introduction of summer time. This disruption may extend to other aspects of seasonal biology in humans. SN - 0960-9822 UR - https://www.unboundmedicine.com/medline/citation/17964164/The_human_circadian_clock's_seasonal_adjustment_is_disrupted_by_daylight_saving_time_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S0960-9822(07)02086-6 DB - PRIME DP - Unbound Medicine ER -