**1. Introduction**

In 2021, 73 nations worldwide conducted DST transitions in a biannual manner, adjusting the clock in order to establish a scenario in which the daylight is maximal utilized for waking activity.

In 2019, the EU Parliament accepted the EU Commission's proposal to abolish the time change in 2021. However, nothing has happened since then. The changeover is now to remain until at least 2026. The basis for the abolition of the clock changeover was a survey of people living in the EU.

In this (non-representative) online survey, 84 percent voted in favor of ending the switch between summer and winter time. A total of 4.6 million people took part, two-thirds of them from Germany [1].

**Citation:** Nohl, A.; Seelmann, C.; Roenick, R.; Ohmann, T.; Lefering, R.; Brune, B.; Weichert, V.; Dudda, M.; The TraumaRegister DGU. Impact of DST (Daylight Saving Time) on Major Trauma: A European Cohort Study. *Int. J. Environ. Res. Public Health* **2021**, *18*, 13322. https://doi.org/10.3390/ ijerph182413322

Academic Editors: Roberto Alonso González Lezcano, Francesco Nocera and Rosa Giuseppina Caponetto

Received: 20 November 2021 Accepted: 15 December 2021 Published: 17 December 2021

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**Copyright:** © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

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The first transition takes place in spring, when the clock is set one hour forwards, and the second in autumn, when the clock is set one hour back again. The main arguments for this adjustment were economic reasons (energy saving) and changing illumination conditions for peak traffic density to likely avoid accidents due to bad light conditions in the evening, when the number of traffic accidents are elevated due to driver fatigue. The rationale of this approach is to shift one extra hour of daylight to the evening hours to compensate for the driver's lack in concentration.

There is evidence that especially the DST transition might have a negative impact on people's health, leading to sleep deprivation and circadian misalignment [2–7]. A study by Kantermann et al. suggests that the human circadian system does not adapt to daylight saving time and that its seasonal adaptation to changing photoperiods is disrupted by the introduction of daylight saving time. This disruption could also affect other aspects of human seasonal biology [3]. Jin et al. used an empirical approach to exploit the end of daylight saving time in a quasi-experimental setting on a daily basis. Due to the time reset in the fall, sleep time was extended by one hour. The study group found significant health benefits as hospital admissions decreased. For example, hospital admissions for cardiovascular disease decreased by 10 per day per million population. Using an event study approach, they found that the effect continued for four days after the time change. Admissions for heart attacks and injuries also showed the same characteristic four-day decline [8]. Toro et al. analyzed the effects of acute light sleep deprivation and circadian rhythm disturbances due to daylight saving time on the incidence of acute myocardial infarction using daily data for Brazil. They found robust evidence of a significant increase (7.4–8.5%) in the number of acute myocardial infarctions in Brazilian states with a time change to summer time but no statistical relationship between states without a time change [9].

A possible connection between DST transition and fatal traffic accidents is controversially discussed in literature. Fritz et al. (2020), for example, found acute consequences of the DST transition in spring on traffic accidents in a chronobiologic context [10]. Here, the spring DST transition increased fatal motor vehicle accidents by 6% in the DST week, whereas the fallback transition in autumn to Standard Time had no effects. Lahti et al. 2011 found that the sleep deprivation after DST transition is not harmful enough to have an influence on the incidence of occupational accident rates [11]. In a recent systematic review, Carey and Sarma addressed the topic about the impact of DST on road traffic collision risk [12]. A total of 24 studies were included in this overview. The complex picture emerging from this review showed day- and time-dependent potentially positive or negative short-term effects of DST and a possible positive long-term effect.

Because of inconsistent findings and conclusions across the mostly heterogeneous studies, no conclusion about a positive or negative overall impact of DST on traffic accidents could be drawn.

Traffic accidents represent only a part of all trauma patients. As a whole, trauma accounts for 10% of deaths worldwide and is the leading cause of death in people younger than 40 years [13]. Therefore, advancements in the prevention of accidents are inevitable. However, external factors such as time of the day, day of the week, and seasons are thought to affect trauma events [14]. Here, it seems obvious that the incidence of traumata might be affected by DST transition markedly.

Previous studies concentrated on the analysis of the impact of DST on traffic accidents, but none investigated the incidence of trauma that occurred from other reasons.

In this present study, our approach was to analyze the very extensive database of the TraumaRegisters DGU®, which has not been used for this purpose thus far and provides an excellent data collection to address the question if DST has an impact on the incidence and impact on major trauma.
