**2. Materials and Methods**

### *2.1. Data Set*

The TraumaRegister DGU® (TR-DGU, AUC - Akademie der Unfallchirurgie GmbH, Munich, Germany) of the German Trauma Society was founded in 1993 to create a multicenter database for pseudonymized and standardized documentation of severely injured patients for quality assurance and research [15].

Participating hospitals are predominantly located in Germany (90%), but an increasing number of hospitals from other countries have also started to contribute their data (e.g., Austria, Belgium, Finland). Currently, approximately 30,000 cases from more than 650 hospitals are entered into the database annually. Participation in TR-DGU is voluntary; however, hospitals associated with TraumaNetzwerk DGU® are required to enter at least a basic dataset for reasons of quality assurance.

Documentation in the TR-DGU includes detailed information on:


Inclusion criteria for the TR-DGU are admission to hospital via the emergency department followed by intensive care or admission to hospital with vital signs and death before admission to the intensive care unit (ICU).

The infrastructure for documentation and data management is provided by the AUC - Academy of Trauma Surgery, a society affiliated with the German Trauma Society. Scientific management is provided by the Committee on Emergency Medicine, Intensive Care and Trauma Management (Sektion NIS) of the German Trauma Society. The scientific evaluation of the data is performed according to a peer-review process defined in the publication guideline of the TR-DGU [15]. The present study complies with the publication guideline of the TR-DGU and is registered under the TR-DGU project ID 2018-047. The inclusion criteria of our study are shown in Figure 1.

Permission by the ethics committee (Ärztekammer Nordrhein/Medical Association North Rhine; no. 310/2018).

**Figure 1.** Inclusion criteria; max = maximum; AIS = abbreviated injury score; DST daylight saving time.

### *2.2. Statistics*

The day of DST change was excluded (usually a Sunday), and a time period of 7 days before and after DST change in spring and autumn was selected for comparison (the comparison of 7 days was chosen because the direct comparison of individual days showed a low number of cases; in the studies cited, the procedure was comparable). Both pre- and post-change phases thus contained each weekday once. Data are presented as number of cases with percentage for counts, and as mean with standard deviation (SD) for metric data. In seriously skewed data, median and inter-quartile range were given instead. Observed differences were evaluated with the chi-squared test or the Mann–Whitney *U*-test.

Statistical analysis was performed using SPSS Statistical software (Version 27.0, IBM Inc., Armonk, NY, USA). The level of statistical significance was set at *p* < 0.05.

The RISC II score was developed and validated using TR-DGU data and represents a summary of the 13 variables, including pattern and severity of injuries, age, sex, prior diseases, and initial physiology [16].

### **3. Results**

A total of 14,807 trauma patients were included in the study. The mean age was 51 (±22) years. The majority were males (71%). In Table 1, the mechanism of accident 1 week before and 1 week after the time change are listed. More traffic accidents occurred after the time change (*n* = 3459 vs. 3582), but it was not statistically significant (*p* = 0.131). The mean ISS was higher after the time change. Although, this difference did not reach the significance level, we observed a strong tendency (*p* = 0.052). There was a noticeable increase in the number of motorcycle and bicycle accidents during the time change from spring to summer (motorcycle *n* = 349 vs. 529, increase of 51.58%; bicycle *n* = 245 vs. 280, increase of 14.29%). After the time change in autumn, these incidents decreased in number compared to the previous week.


**Table 1.** Impact of daylight saving time change in patients with major trauma.

*DST* = daylight saving time.

Table 2 shows demographics and the distribution of different injury regions before and after the time change. Increased deaths after time change *n* (%) = 900 (12.2) vs. 950 (12.8). The age, injury severity, expected mortality (RISC II), ICU, and hospitalization days are shown in Table 3.

**Table 2.** Cross tabulation.


AIS = abbreviated injury scale, *DST* = daylight saving time.

**Table 3.** Impact of DST in major trauma—spring and autumn.


DST = daylight saving time, ICU = intensive care unit, ISS = Injury Severity Score, IQR = interquartile range, RISC II = Revised Injury Severity Classification II, SD = standard deviation.

#### **4. Discussion**

The results of this study showed an increased incidence of traffic accidents (bicycle and motorcycle) after the spring DST. Motorcycle accidents showed an increase of 51.58%, whereas accidents involving motorcyclists slightly decreased again after the time change in autumn. However, it is worth mentioning that many motorcyclists have summer license plates from March to October. Central European Summer Time begins on the last Sunday in March at 2:00 CET. Therefore, there is an interval of over 4 weeks from the seasonal registration of the motorcycles to the change of time.

However, a possible cause could also be the general trend that motorcycle and bicycle accidents occur more frequently in the summertime and decrease again in the winter. External influences, such as time of day, lighting conditions, days of the week, weather conditions, and temperatures were not considered in our study.

The number of registered motorcycles in Germany has risen steadily, reaching 4.31 million in 2017. We detected 10 of the busiest highways in the most populous state of North Rhine-Westphalia and compared 10 automatic counting stations for traffic measurement between March 2017 and April 2017. The 10 automatic counting stations counted 5848 motorcycles in March 2017 and 6362 motorcycles in April 2017. Thus, there is an increase of 8.79% in the number of motorcycles counted on the 10 busiest highways in North Rhine-Westphalia from March to April. The increase of 8.79% more motorcycles counted from March to April contrasts with the 51.58% increase in motorcyclists seriously injured after the time change in spring. Although only 10 measuring points were evaluated, the sample of a total of 12,210 was representative. However, a sample of a German state is compared here with a European cohort in our study [17].

A comparable study by Pape-Köhler et al. (2014) showed that the time of day shows a high variation in the incidence of trauma. In particular, the frequency of accidents increased during rush hour [14]. However, these external factors could also have an influence on accident frequency. In addition, our data do not show whether the motorcyclists caused the traffic accidents themselves or were harmed by other road users.

Importantly one should take into account that due to our inclusion criteria, only accidents with serious injuries were considered. Thus, no conclusion can be drawn about the general frequency of accidents.

Fritz et al. (2020) showed similar results in their study. The study group was able to show that the incidence of serious car accidents increased by 6% after the time change in spring. They attributed the result to sleep deprivation due to the one-hour time shift. Here, the frequency of accidents was increased, especially in the early morning hours. The research team concluded that leaving out the time change could prevent up to 27 serious traffic accidents annually [10].

Besides the disturbance of the circadian rhythm, another reason could be the fact that due to the time shift by one hour later, it is correspondingly darker in the early morning and thus an increased accident frequency could be explained.

In a study by Robb et al. (2018), an increased accident frequency was proven in the first 2 days after the time change in New Zealand [18].

Another study from Spain showed that the time change is associated with fatal accidents of 1.5 people per year in 52 Spanish capital cities [19].

What is slightly noticeable in our study is the increased accident frequency explicitly among motorcyclists. There are a number of confounding factors that influence the frequency of motorcycle accidents. The biggest disruptive factors are certainly the winter break and a colder season at the beginning of the motorcycle season. It has been proven that the frequency of accidents increases with age (young, inexperienced riders, as well as seniors), general riding experience and frequency, weight of the motorcycle, male gender, weather conditions, etc. [20].

However, here, the period of 1 week before and 1 week after the time change was quite short to conclude.

Thus, according to our results, if the time change were eliminated, up to 12 serious motorcycle accidents could be prevented each year if these accidents were indeed related to DST.

However, we cannot confirm this statement with a probability bordering on certainty. Nevertheless, due to the external influences not taken into account and the lack of statistical significance, it should rather be seen as a tendency. Our result is certainly not conclusive enough for a clear recommendation.
