Summertime and the drivin' is easy? Daylight saving time and vehicle accidents.

We investigate how exogenous variation in daylight caused by Daylight Saving Time affects road safety as measured by the count of vehicle crashes. We use administrative daily data from Greece covering the universe of all types of recorded vehicle accidents during the 2006-2016 period. Our regression discontinuity estimates support an ambient light mechanism that reduces the counts of serious vehicle accidents during the Spring transition and increases the count of minor ones during the Fall transition. The effects are driven from the hour intervals that are mostly affected from seasonal clock changes. We then discuss the potential cost implications of those seasonal transitions. In light of the talks about abolishing seasonal clock changes in the European Union (EU), our findings are policy relevant and can inform the public debate as empirical evidence for the block is scarce.

The Alarm Clock Against the Sun: Trends in Google Trends Search Activity Across the Transitions to and from Daylight Saving Time.

The human circadian timing system depends on the light/dark cycle as its main cue to synchronize with the environment, and thus with solar time. However, human activities depend also on social time, i.e. the set of time conventions and restrictions dictated by society, including Daylight Saving Time (DST), which adds an hour to any degree of desynchrony between social and solar time. Here, we used Google Trends as a data source to analyze diurnal variation, if any, and the daily peak in the relative search volume of 26 Google search queries in relation to the transitions to/from DST in Italy from 2015 to 2020. Our search queries of interest fell into three categories: sleep/health-related, medication and random non sleep/health-related. After initial rhythm and phase analysis, 11 words were selected to compare the average phase of the 15 days before and after the transition to/from DST. We observed an average phase advance after the transition to DST, and a phase delay after the transition to civil time, ranging from 25 to 60 minutes. Advances or delays shorter than 60 minutes, which were primarily observed in the sleep/health-related category, may suggest that search timing for these queries is at least partially driven by the endogenous circadian rhythm. Finally, a significant trend in phase anticipation over the years was observed for virtually all words. This is most likely related to an increase in age, and thus in earlier chronotypes, amongst Google users.

Driving fatigue increases after the Spring transition to Daylight Saving Time in young male drivers: A pilot study.

The Spring transition to Daylight Saving Time (DST) has been associated with several health and road safety issues. Previous literature has focused primarily on the analysis of historical crash and hospitalization data, without investigating specific crash contributing factors, such as driving fatigue. The present study aims to uncover the effects of DST-related circadian desynchrony and sleep deprivation on driving fatigue, by means of a driving simulator experiment. Eighteen participants (all males, age range 21-30 years, mean = 24.2, SD = 2.9) completed two 50-minute trials (at one week distance, same time and same day of the week) on a monotonous highway environment, the second one taking place in the week after the Spring transition to DST. Driving fatigue was evaluated by analysing several different variables (including driving-based, physiological and subjective indices) and by comparison with a historical cohort of pertinent, matched controls who had also undergone two trials, but in the absence of any time change in between. Results showed a considerable rise in fatigue levels throughout the driving task in both trials, but with significantly poorer performance in the post-DST trial, documented by a worsening in vehicle lateral control and an increase in eyelid closure. However, participants seemed unable to perceive this decrease in their alertness, which most likely prevented them from implementing fatigue-coping strategies. These findings indicate that DST has a detrimental effect on driving fatigue in young male drivers in the week after the Spring transition, and provide valuable insights into the complex relationship between DST and road safety.

Saving light, losing lives: How daylight saving time impacts deaths from suicide and substance abuse.

This paper estimates the impact of Daylight Saving Time (DST) on deaths from suicide and substance abuse in the United States. Using Multiple Cause-of-Death Mortality Data from the National Vital Statistics System of the National Center for Health Statistics from 1979 to 1988, the effect is identified in two ways: a regression discontinuity design that exploits discrete time changes in the Spring and Fall; and a fixed effects model that uses a policy change and a switching mechanism that introduces random variation to DST's start and end dates. This is one of the first attempts to estimate the impact of DST on deaths due to suicide and substance abuse and the first to use either identification strategy. The results from both methods suggest that the sleep disruptions during the Spring transition cause the suicide rate to rise by 6.25 percent and the death rate from suicide and substance abuse combined to increase by 6.59 percent directly after the time change. There is no evidence for any change in these outcomes during the Fall transition. The contrasting results from Spring to Fall suggest the entire effect can be attributed to disruptions in sleep patterns rather than changes in ambient light exposure.

Assessment of the number of admissions for road traffic collisions and severity of injury in daylight saving time and permanent daylight saving time periods.

BACKGROUND/AIM: Permanent daylight saving time has been implemented in Turkey since 2016. The present study determines the characteristics of road traffic collisions in the short-term, trauma severity, and whether permanent daylight saving time has an impact on these parameters. MATERIALS AND METHODS: Drivers admitted because of road traffic collisions to a tertiary care university hospital emergency service two weeks before and after the transition to wintertime in 2014 and 2015 and summertime in 2015 and 2016 as well as those admitted two weeks before and after the same period with permanent daylight saving time in 2016 and 2017 wintertime and 2017 and 2018 summertime were included in the study. Trauma severity was measured using the Injury Severity Score. RESULTS: The study analysed the data of 710 patients. There was no statistically significant difference was found between admissions in the summertime and permanent daylight saving time periods in terms of gender, time of admission, week of admission, Injury Severity Score and outcome (P > .05 for all values). CONCLUSIONS: In this study, we examined the short-term effects of daylight saving time on road traffic collisions, and demonstrated that it had no impact on the number or time of admission, trauma severity and patient outcomes. More comprehensive studies covering longer periods can be performed across the country.

Effect of Daylight Saving Time clock shifts on white-tailed deer-vehicle collision rates.

To devise effective measures for reducing hazardous wildlife-vehicle collisions, it is necessary to know when during the year accidents occur most frequently, and what factors cause the seasonal patterns. Daylight Saving Time (DST) 1-h clock-shifts around the spring and fall equinoxes at temperate zone latitudes are associated with increased vehicle accidents, attributed to driver error caused by disrupted sleep patterns and changes in visibility during peak driving times. Collision with deer is a significant cause of motor vehicle accidents in North America; in New York State alone, 65,000 vehicle accidents annually are caused by collision with white-tailed deer (Odocoileus virginianus). We asked whether white-tailed deer-vehicle collisions (DVC) increased in frequency after DST clock shifts in New York State, by analyzing 35,167 New York State DVC reports from 2005 to 2007. For the spring, when the clock is shifted an hour forward relative to sunrise (i.e. later sunrise and sunset), there was either no change or possibly a small decrease in workweek evening DVC after the clock shift. For fall, when the clock is shifted an hour back relative to sunrise (i.e. earlier sunrise and sunset), the DVC rate was far higher than spring. The DVC rate was higher after the clock shift than before, caused in part by an ongoing seasonal trend for increasing DVC associated with deer behavior around the time of rut, peaking about two weeks after the clock shift. However, there was also a reduction in workweek morning DVC after clock-shift, but an even greater increase in DVC in the evening. DVC rates are highest around dusk and during the fall, and the fall DST clock-shift caused more workweek commuter traffic to coincide with the annual hourly period of peak risk of DVC. We conclude that in New York State, DST clock-shift results in an increase in the number of DVC, and therefore injuries and property damage associated with such accidents. The justification for DST clock-shifts is controversial; when evaluating the benefits and costs, one should include the consequences for risk of wildlife-vehicle collisions, especially in regions where ungulate-vehicle accidents are frequent, and clock-shifts coincide with the rut or other periods of peak accident risk.

Daylight saving time does not seem to be associated with number of percutaneous coronary interventions for acute myocardial infarction in the Netherlands.

BACKGROUND: In multiple studies, the potential relationship between daylight saving time (DST) and the occurrence of acute myocardial infarction (MI) has been investigated, with mixed results. Using the Dutch Percutaneous Coronary Intervention (PCI) registry facilitated by the Netherlands Heart Registration, we investigated whether the transitions to and from DST interact with the incidence rate of PCI for acute MI. METHODS: We assessed changes in hospital admissions for patients with ST-elevation myocardial infarction (STEMI) or non-STEMI (NSTEMI) undergoing PCI between 1 January 2015 and 31 December 2018. We compared the incidence rate of PCI procedures during the first 3 or 7 days after the transition with that during a control period (2 weeks before transition plus second week after transition). Incidence rate ratio (IRR) was calculated using Poisson regression. Potential gender differences were also investigated. RESULTS: A total of 80,970 PCI procedures for STEMI or NSTEMI were performed. No difference in incidence rate a week after the transition to DST in spring was observed for STEMI (IRR 0.95, 95% confidence interval (CI) 0.87-1.03) or NSTEMI (IRR 1.04, 95% CI 0.96-1.12). After the transition from DST in autumn, the IRR was also comparable with the control period (STEMI: 1.03, 95% CI 0.95-1.12, and NSTEMI: 0.98, 95% CI 0.91-1.06). Observing the first 3 days after each transition yielded similar results. Gender-specific results were comparable. CONCLUSION: Based on data from a large, nationwide registry, there was no correlation between the transition to or from DST and a change in the incidence rate of PCI for acute MI.

Daylight saving time and the incidence of thrombolysis to treat acute ischemic stroke.

BACKGROUND: Twenty-five percent of the global population lives in one of the more than 70 countries that observe daylight saving time (DST). These people are exposed to 1hour of time transition twice a year, influencing the circulatory system. We aimed to analyze the incidence of thrombolysis to treat acute ischemic stroke in relation to clock changes in Hungary over a 10-year period. METHODS: The number of thrombolytic treatments performed within the period between 2006 and 2015 was analyzed. Anonymized nationwide data on the dates and exact daily numbers of thrombolysis interventions were provided by the National Health Insurance Fund. We compared the mean number of thrombolytic treatments on the day before with that on the day after each transition, and also between the preceding and following one week and month. RESULTS: Our data including the last days of each month suggested a significant increase in thrombolysis numbers both in spring and in autumn on the day and the week after the clock change. However, when the last days of each month were excluded from analysis (as this in itself was associated with a 7-fold increase in stroke incidence in our earlier study), no significant difference in the number of thrombolysis treatments between the days and weeks before and after the clock change was detectable. The long-term, monthly analysis also did not reveal a significant difference. CONCLUSIONS: Our findings reflect that psychosocial factors, such as the approach of the last day of the month override the intrinsic effect of disturbances of the circadian rhythm on stroke incidence.

Daylight saving time transitions are not associated with increased seizure incidence.

OBJECTIVE: Given the known association of daylight saving time (DST) transitions with increased risk of accidents, heart attack, and stroke, we aimed to determine whether seizures, which are reportedly influenced by sleep and circadian disruption, also increased in frequency following the transition into DST. METHODS: Using Seizure Tracker's self-reported data from 12 401 individuals from 2008-2016, 932 717 seizures were assessed for changes in incidence in relation to DST transitions. Two methods of standardization-z scores and unit-scaled rate ratios (RRs)-were used to compare seizure propensities following DST transitions to other time periods. RESULTS: As a percentile relative to all other weeks in a given year, absolute seizure counts in the week of DST fell below the median (DST seizure percentiles mean ± SD: 19.68 ± 16.25, P = 0.01), which was concordant with weekday-specific comparisons. Comparatively, RRs for whole-week (1.06, 95% confidence interval [CI] 1.02-1.10, P = 0.0054) and weekday-to-weekday (RR range 1.04-1.16, all P < 0.001) comparisons suggested a slightly higher incidence of seizures in the DST week compared to all other weeks of the year. However, examining the similar risk of the week preceding and following the DST-transition week revealed no significant weekday-to-weekday differences in seizure incidence, although there was an unexpected, modestly decreased seizure propensity in the DST week relative to the whole week prior (RR 0.94, 95% CI 0.91-0.96, P < 0.001). SIGNIFICANCE: Despite expectations that circadian and sleep disruption related to DST transitions would increase the incidence of seizures, we found little substantive evidence for such an association in this large, longitudinal cohort. Although large-scale observational/epidemiologic cohorts can be effective at answering such questions, additional covariates (eg, sleep duration, seizure type, and so on) that may underpin the association were not able available, so the association has not definitively been ruled out.

The controversial debate about daylight saving time (DST)-results of a retrospective forensic autopsy study in Frankfurt/Main (Germany) over 10 years (2006-2015).

Worldwide, many people are exposed to biannual time changes. The benefit of Daylight Saving Time (DST) is controversially discussed and its impact on human health is largely unknown. The present study examines, whether effects of these time changes are seen in a forensic autopsy database. The mortality study is based on autopsy protocols provided by the Institute of Legal Medicine, University Clinic of the Goethe-University Frankfurt/Main, covering a period of 10 years (2006-2015). Data regarding mode and cause of death, age, and gender were evaluated for 4 weeks around the transition to and from DST in spring and autumn. A significant (p = 0.04) elevation in the number of autopsies was observed in the first week following the switch to DST in spring, but no significant changes were noted in autumn. Gender-specific analysis indicated that the autopsy rate of females showed a significant (p = 0.01) peak in the first and a decline (p = 0.05) in the second week following the switch to DST. Differences in non-natural death cases primarily included traffic accidents and suicides, in natural death cases fatal cardiac diseases like cardiac insufficiency and acute myocardial infarction. The number of suicides was low (p = 0.05) before, but high (p = 0.07) in the weeks after the introduction of DST. The present evaluation confirmed a potential effect of DST, such as a significant higher autopsy rate in spring during the first week after the introduction to DST. Moreover, a relation between the introduction to DST in spring and an increase in suicide cases was observed.

Sleepy Punishers Are Harsh Punishers.

The degree of punishment assigned to criminals is of pivotal importance for the maintenance of social order and cooperation. Nonetheless, the amount of punishment assigned to transgressors can be affected by factors other than the content of the transgressions. We propose that sleep deprivation in judges increases the severity of their sentences. We took advantage of the natural quasi-manipulation of sleep deprivation during the shift to daylight saving time in the spring and analyzed archival data from judicial punishment handed out in the U.S. federal courts. The results supported our hypothesis: Judges doled out longer sentences when they were sleep deprived.

Self-reported discomfort associated with Daylight Saving Time in Brazilian tropical and subtropical zones.

BACKGROUND: Daylight Saving Time (DST) annually moves clocks 1 hour forward, when daytime is longer than night. Previous studies from medium and high latitude locations have pointed to a disruptive effect of DST on human circadian rhythms. Since Brazil is an equatorial country implementing DST, a different relationship between photic and social synchronisers may interfere with DST effects. AIM: To explore the prevalence and duration of self-reported discomfort related to DST among Brazilian residents (latitude 12-33° S, longditude 39-57° W). It was hypothesised that an elevated prevalence of self-reported discomfort would be found in Brazil, due to the pronounced uncoupling between social and geophysical synchronisers. SUBJECTS AND METHODS: In total, 12 467 volunteers completed a web-based, Brazilian version of Horne-Östberg Morningness-Eveningness Questionnaire, provided demographic information, and answered questions related to DST complaints (discomfort, duration of discomfort). RESULTS: Of the total sample, 45.43% reported no discomfort related to DST, with meaningful proportions for all chronotypes. However, eveningness was most associated with discomfort. About one fourth of the total sample reported discomfort over the whole DST period. Gender interaction is largely supported by these results. CONCLUSIONS: DST at low latitude locations may be disruptive for circadian rhythms, since seasonality of sunrise near the equator is negligible or very mild.

Does the transition into daylight saving time really cause partial sleep deprivation?

AIM: To identify possible changes in the sleep patterns according to chronotype in undergraduate students during the daylight saving time (DST) transition. METHODS: A total of 378 students answered the Morningness-Eveningness Questionnaire (MEQ) to determine their chronotype and kept a diary about sleep-wake schedules 1 week before and after the DST transition. Oral mucosal cell samples were collected for genetic analysis. RESULTS: After the DST transition, intermediate types (I-types) delayed bedtime and increased their time in bed and all groups delayed their wake-up time. All groups presented a shorter phase angle between sunset and the bedtime after the DST transition. On the other hand, only E-types showed a tendency to reduce the phase angle between sunrise and wake-up time, while I-types and M-types kept the same phase angles between sunrise and wake-up time after the DST transition. The polymorphisms in the human genes CLOCK and PER3 were not associated with individual differences in sleep patterns, nor were they associated with an adjustment to the DST transition. CONCLUSION: Under the new set of social times determined by DST, the adjustment was only partial. I-types delayed bedtime and all groups delayed their wake-up times after the beginning of DST. Consequently, the time in bed after the DST transition was not reduced; Morning (M-types) and Evening-types (E-types) kept the same time in bed and I-types showed an increase on it.

Parkinson's patients cope with daylight saving time.

Disturbances of the circadian timing system following daylight saving time (DST) may influence the symptoms of Parkinson's disease (PD). To address this question, we compared the severity of motor fluctuations and non-motor symptoms both before and after the time change. Total daily "off-time" based on diaries, excessive daytime sleepiness (Epworth Sleepiness Scale), depressive symptoms (Beck Depression Inventory), and psychosis associated with PD were assessed both before and after the DST. Eighty-three PD patients (mean age, 67±7.7years; mean disease duration, 10.4±6.4years) were included. Thirty-six patients had motor fluctuations (mean daily "off-time", 4.8±2.4h/day). There was no significant variation of the total daily "off-time" (2.5±2.6h/day versus 2.5±2.7h/day), ESS (8.3±4.8 versus 8.1±4.9), BDI (10.4±6.2 versus 10.0±6.9), or PAPD (1.4±1.6 versus 1.1±1.6) scores (P>0.05) after DST. Our results suggest that PD patients cope relatively well with DST.

Permanent standard time is the optimal choice for health and safety: an American Academy of Sleep Medicine position statement.

The period of the year from spring to fall, when clocks in most parts of the United States are set one hour ahead of standard time, is called daylight saving time, and its beginning and ending dates and times are set by federal law. The human biological clock is regulated by the timing of light and darkness, which then dictates sleep and wake rhythms. In daily life, the timing of exposure to light is generally linked to the social clock. When the solar clock is misaligned with the social clock, desynchronization occurs between the internal circadian rhythm and the social clock. The yearly change between standard time and daylight saving time introduces this misalignment, which has been associated with risks to physical and mental health and safety, as well as risks to public health. In 2020, the American Academy of Sleep Medicine (AASM) published a position statement advocating for the elimination of seasonal time changes, suggesting that evidence best supports the adoption of year-round standard time. This updated statement cites new evidence and support for permanent standard time. It is the position of the AASM that the United States should eliminate seasonal time changes in favor of permanent standard time, which aligns best with human circadian biology. Evidence supports the distinct benefits of standard time for health and safety, while also underscoring the potential harms that result from seasonal time changes to and from daylight saving time. CITATION: Rishi MA, Cheng JY, Strang AR, et al. Permanent standard time is the optimal choice for health and safety: an American Academy of Sleep Medicine position statement. J Clin Sleep Med. 2024;20(1):121-125.

Impact on health outcomes associated with changing the clock 1 hour during fall and spring transitions in the Southern Hemisphere.

STUDY OBJECTIVES: Changing the clocks seasonally is potentially harmful because it interferes with normal daytime activities. Studies aimed at quantifying this association are scant. The objective of this study was to determine the effects of 1 year's worth of changing the clocks (fall and spring transitions) on healthy young men located in the Southern Hemisphere in South America. METHODS: We performed an observational prospective study. Thirty healthy male university students were evaluated from 2 weeks before to 2 weeks after both the fall and spring transitions. We administered an overall sleep questionnaire, assessed quality of life, recorded 7-day wrist actigraphy, and had participants perform a psychomotor vigilance task. We defined the 1-hour clock change as the primary exposure and the change in psychomotor vigilance task lapses of 500 milliseconds or more in response time as our primary outcome. Changes were evaluated by the Wilcoxon rank test (significance: P < .05). RESULTS: After the fall transition, we found a significant worsening in psychomotor vigilance task performance (median [interquartile range], 9.9 [6.0-14.3] lapses of ≥ 500 milliseconds in response time at baseline vs 16.8 [8.2-28.0] after transition; P < .002). Additionally, we found a median loss of about 1 hour of total sleep time and time in bed after the fall transition. Furthermore, participants presented with insomnia. Performance on the psychomotor vigilance task was also affected after the spring transition (16.7 [10-23] vs 23 [12.2-32.2]; P < .001). CONCLUSIONS: A decrease in performance in neurocognitive tests was found after both time transitions. The transition led to insomnia and a significant worsening of sleep variables. CITATION: Labarca G, Henriquez-Beltrán M, Sanhueza R, et al. Impact on health outcomes associated with changing the clock 1 hour during fall and spring transitions in the Southern Hemisphere. J Clin Sleep Med. 2024;20(6):887-893.

The practice of Daylight Saving Time in Canada: Its suitability with respect to sleep and circadian rhythms.

Daylight Saving Time (DST) is the practice of setting the clocks one hour forward from Standard Time (ST) in the spring and back again to ST in the fall. This commentary discusses the impact of bi-annual time changes on sleep and circadian rhythms and suggests avenues to minimize negative outcomes on the well-being of Canadian citizens. Ideally, ST should be close to solar time, meaning that daylight is equally distributed before and after noon time, i.e., when the sun is at its highest point in the sky. In Canada, some provinces are proposing to opt out of DST to either return to constant ST throughout the year or to implement permanent DST. National and international associations of clinicians and researchers on sleep and biological rhythms and in health sciences have positioned themselves in favour of permanent ST. In Canada, the Canadian Sleep Society and the Canadian Society for Chronobiology have also issued such a position. This commentary focuses on the implications of previous research findings for sleep and health in Canada given its northern geographical location. It concludes with a research agenda focusing on the Canadian context.

RéSUMé: L'heure avancée (HA) consiste à avancer les horloges d'une heure par rapport à l'heure normale (HN) au printemps et à revenir à l'HN à l'automne. Le but de ce commentaire est de traiter de l'impact des changements d'heure semestriels sur le sommeil et les rythmes circadiens et de proposer des moyens d'en minimiser les conséquences négatives sur le bien-être des citoyens canadiens. Idéalement, l'HN devrait être proche de l'heure solaire, ce qui signifie que la lumière du jour est répartie de manière égale avant et après midi, c'est-à-dire lorsque le soleil est à son point culminant dans le ciel. Au Canada, certaines provinces proposent de renoncer à la pratique du changement d'heure pour revenir à une HN constante tout au long de l'année ou mettre en place l'HA de façon permanente. Des associations nationales et internationales de cliniciens et de chercheurs sur le sommeil, les rythmes biologiques et les sciences de la santé se sont prononcées en faveur de l'HN permanente. Au Canada, la Société canadienne du sommeil et la Société canadienne de chronobiologie ont adopté la même position. Le commentaire est centré sur les retombées des résultats de recherches antérieures pour le sommeil et la santé au Canada, compte tenu de sa situation géographique nordique. Il se termine par un programme de recherche axé sur le contexte canadien.

Do sleep disruptions promote social fragmentation?

Sleep changes predate shifts in mood/affect, thought processing, mental and physical health, civic engagement, and contextual circumstances, among other things. Theory predicts that these changes may lead to shifts in political and social beliefs. Do sleep disruptions shape how individuals see the world, the people around them, and themselves in relation to others? In this article, we use daily survey data from the 77 waves (N ≈ 460,000) of the University of California, Los Angeles's 2019-2021 Nationscape Survey-a nationally representative political survey-to examine the effect of an exogenous short-term sleep disruption on measures of political views, polarization, and discriminatory beliefs. Using this data set, we leverage the modest sleep disruption that occurs at the start (and end) of Daylight Saving Time (DST) and employ a regression discontinuity in time design around the precise DST cutoff (which we supplement with event study models). Despite strong theoretical expectations and correlational connection between measures of sleep and many outcomes related to social fragmentation, we find that the DST change has little to no causal effect on citizens' levels of polarization or their discriminatory attitudes. These effects are precise enough to rule out small effects, robust to a host of specification checks, and consistent across potential subgroups of interest. Our work adds to a small but growing body of research on the social and political effects of sleep disruptions.

The Effects of Daylight Saving Time (DST) Transition Cancelation on Work Accidents of Turkey.

Objectives. Turkey canceled the daylight saving time (DST) transition and started permanent clock application. Considering the effect of this new regulation on working hours, this study examines whether there is a relationship with the increase in the number of work accidents in shifts. Methods. Data on work accidents were obtained from the Republic of Turkey Social Security Institution (SSI), filed between 2011 and 2020. We estimate accident rates using Poisson regression and log-linear models as a function of a variety of date-based factors. Results. The results show that DST transition is effective (ineffective in terms of gender) on changes in the number of work accidents. With statistical analyses, the hourly distribution of work accidents was determined, indicating at which hour the most work accidents occurred, using the work accident frequency rate. The number of prevented work accidents was calculated as 286,793 for Turkey. Conclusion. The findings from these studies suggest that cancellation of the DST transition does not have a negative effect on the incidence of work accidents in Turkey; on the contrary, this practice also serves the purpose of preventing work accidents.

Being robbed of an hour of sleep: The impact of the transition to Daylight Saving Time on work engagement depends on employees' chronotype.

OBJECTIVE: Worldwide, over 70 countries advance their clocks in spring to Daylight Saving Time. Previous research has already demonstrated that the clock change negatively impacts employees at work. However, this research implicitly assumed that the clock change affects everyone to the same extent. In the current study, we propose that the massively prevalent Daylight Saving Time transition may have an effect on employees' sleep and their work engagement that is dependent upon employees' chronotype. METHODS: We conducted a longitudinal study with 155 full-time employees who filled out online surveys on three Mondays around the transition to Daylight Saving Time. RESULTS: Results showed that the transition to Daylight Saving Time resulted in decreased work engagement measured 1day as well as 1week after the transition to Daylight Saving Time. Lower sleep quality (but not shorter sleep duration) partly explained this effect. The negative effect of the transition to Daylight Saving Time on work engagement 1day after the transition was more pronounced for employees with later chronotypes ("owls") than for those with earlier chronotypes ("larks"). CONCLUSION: In summary, our study shows that the transition to Daylight Saving Time has an adverse short-time impact on private life and working life and should, therefore, also be considered in organizations. Because later chronotypes are especially prone to adverse effects of the transition, interventions targeted for this group might be especially helpful.