Sleep researchers have been advocating already for a long time starting school later. This is above all important for adolescents and young adults, since their sleep rhythm is especially late due to physiological reasons [Roen13, VoRa15].
With daylight saving time we do the opposite: Instead of 7:30 a.m., schools will start at 6:30 a.m. (see Figure 1), masked by the artificial renaming of the time, which has at best a placebo effect on our internal clock and therefore our feeling for tiredness.
Teenagers suffer from on school days from substantial sleep deprivation [BoPK10, Voll12]. This is, in addition to health risks, such as increased stress, depression, metabolic abnormalities, obesity and a weakened immune system, associated with traffic accidents, consumption of stimulants, and poorer school grades [Voll12].
Figure 1: School and work start is earlier during Daylight Saving Time.
Sleep is essential for performance. However, the correct timing plays a huge role [VoRa15], and that is dependent on Chronotype. Early chronotypes can fall asleep early in the evening and wake up early in the morning without an alarm clock. Late chronotypes, on the other hand, have a later sleep window for physiological reasons. The melatonin release and lowering of body temperature necessary for sleep take place later than with earlier types. However, only 20% of the population are early chronotypes. 20% are late chronotypes and the rest is somewhere in between. The situation is even worse for adolescents and young adults: only 8% are early and 35% are late chronotypes. [VoRa15]
Unfortunately, our school schedules only align with the biological sleep needs for the few early chronotypes. Students in the 9th grade develop a daily sleep deficit of 100 minutes on school days [VoRa15]. On weekends, they sleep an average 3 hours and 8 minutes later, which means they suffer from more than 3 hours of social jetlag [VoRa15]. For late chronotypes types, the social jetlag is even more than 4 hours [Voll12].
but it is not only the sleep deprivation but also the time for best performance and highest attention that depends on chronotype. Only early chronotypes are more focused in the morning than in the afternoon. For the others, the majority of the students, performance and attention increases throughout the day. Their performance capacity and attentiveness are higher in the afternoon than early in the morning. In performance tests, young people perform much better at 1 p.m. than 7:30 a.m., which is due to a more efficient working memory in the afternoon (1 p.m. - 5 p.m.). [VoRa15]
Studies show: the later the chronotype, the worse the grades, with the chronotype even having a greater impact than the duration of sleep [ToNR15, VoRa15]. That means: more important than how long you sleep is when you sleep! Studies with university students come to comparable results [VoRa15].
Since our internal clock is set by light and primarily by the sun (see also Myth: “You get used to it“), daylight saving time means that - measured by the clock - people fall asleep later and wake up later. Therefore, by daylight saving time we create later sleep types [Bori10, HEGR14, RoKM07]. This was confirmed by a study over a three-year test period on permanent daylight saving time in Russia (2011 - 2014) [BTPK17]: the chronotypes became later, social jetlag increased, and school grades became worse - compared to seasonal daylight saving time. The subsequent introduction of permanent standard time resulted in the smallest social jet lag and the best school grades.
With seasonal and, above all, permanent daylight saving time, we particularly burden the health and performance of our children and that of young adults - the future key players of our society. If we stand up for education, science and good work in our country, only geographically correct time zones, without daylight saving time, can be an option.