Daylight Saving Time Transitions Research Articles

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.

About time: Daylight Saving Time transition and individual well-being

Daylight Saving Time is controversial due to its alleged negative impact on individual well-being. Using panel data from Germany we find evidence that the transition to summer time has negative influence on general life satisfaction and mood, which is stronger for those in full time employment.

Daylight saving time transitions and acute myocardial infarction

Most recently, the possible impact of transitions to and from daylight saving time (DST) on the increased incidence of acute myocardial infarction (AMI) has been suggested. The goal of this report was to analyze independent influence of DST transitions on the incidence of AMI with simultaneous control for the confounding presence of situational triggers such as physical exertion, emotional stress, heavy meals, and sexual intercourse, as well as for other clinical factors. Detailed information was obtained from 2412 patients and included baseline characteristics, working status, exact time of AMI, possible external triggers, cardiovascular risk factors, and prehospital medication. AMI incidence on days after the DST was compared with incidence during control periods and patient characteristics, cardiovascular medication, and circumstances of AMI were evaluated to identify potential risk modifiers. Relative risks of AMI and differences in patient characteristics were expressed through incidence ratios and odds ratios, respectively, with 95% confidence intervals (CIs). Multivariate analysis was performed by using a stepwise multiple regression to assess the independent predictive significance of the characteristics of patients for the AMI occurring in the posttransitional period. The incidence ratio for AMI for the first four workdays after the spring DST transition was 1.29 (95% CI: 1.09–1.49) and the excess was particularly prominent on Monday. In autumn, the incidence ratio for AMI for this 4-d period was 1.44 (95% CI: 1.19–1.69), with peaks on Tuesday and Thursday. The independent predictors for AMI during this period in spring were male sex (p = 0.03) and nonengagement in physical activity (p = 0.02) and there was a trend for the lower risk of incident among those taking calcium antagonists (p = 0.07). In autumn, the predictors were female sex (p = 0.04), current employment (p = 0.006), not taking β-blocker (p = 0.03), and nonengagement in physical activity (p = 0.02). The present report supports the possibility that DST transitions represent additional chronobiological feature of AMI, and that risk of an onset varies according to sex, employment status, and the taking of cardiovascular medication. (Author correspondence: viktor.culic@st.t-com.hr)

Work-related accidents and daylight saving time in Finland

Recent research has indicated that transitions into and out of daylight saving time (DST) unbalance the physiological circadian rhythm and may lead to sleep disturbance. Sleep deprivation may have negative effects on motivation, attention and alertness and thus it is possible that transitions into and out of DST may increase accident rates. To explore the impact of DST transitions on the number of occupational accidents in Finland. For the study, we analysed all occupational accidents that happened in Finland 1 week before and 1 week after DST transitions during the years 2002-06. Transitions into and out of DST did not significantly increase the number of occupational accidents. It seems that sleep deprivation after DST transition is not harmful enough to impact on occupational accident rates.

Daylight saving time transitions and road traffic accidents.

Circadian rhythm disruptions may have harmful impacts on health. Circadian rhythm disruptions caused by jet lag compromise the quality and amount of sleep and may lead to a variety of symptoms such as fatigue, headache, and loss of attention and alertness. Even a minor change in time schedule may cause considerable stress for the body. Transitions into and out of daylight saving time alter the social and environmental timing twice a year. According to earlier studies, this change in time-schedule leads to sleep disruption and fragmentation of the circadian rhythm. Since sleep deprivation decreases motivation, attention, and alertness, transitions into and out of daylight saving time may increase the amount of accidents during the following days after the transition. We studied the amount of road traffic accidents one week before and one week after transitions into and out of daylight saving time during years from 1981 to 2006. Our results demonstrated that transitions into and out of daylight saving time did not increase the number of traffic road accidents.

Abrupt Shift of the Pattern of Diurnal Variation in Stroke Onset With Daylight Saving Time Transitions

Stroke onset shows a pattern of diurnal variation, with a peak in morning hours. Rhythmic changes in blood pressure, hormones, and other parameters have been suggested as underlying mechanisms, but exogenous factors such as increasing physical activity after awakening may also be of relevance. To characterize the impact of external clock changes on the rhythmic variation in stroke onset, this parameter was recorded in patients during transition periods into and out of Daylight Saving Time (DST). The present study was based on a prospective stroke registry in Germany that contains time points of stroke onset from 44 251 patients admitted between 2000 and 2005. To achieve a uniform timeline, time points of stroke onset were set back from Central European Summer Time (CEST) to Central European Time (CET) for patients admitted during DST periods. Compared with the last week before the clock change, transition to or from DST resulted in an immediate shift of stroke onset time points within the first week after the clock change in reference to the uniform timeline (transition from CET to CEST -60 minutes for the time points in both the 25th and 50th percentiles of the diurnal pattern, P<0.001; transition from CEST to CET +60 minutes for the time points in both the 25th and 50th percentiles, P<0.001; patients pooled on a weekly basis). A significant shift was already present the first and second day after the transitions (ie, Monday and Tuesday). Transition to or from DST is coupled with an immediate shift in the time pattern of stroke onset. This strengthens the idea that exogenous factors associated with awakening are important determinants of the pattern of diurnal variation of stroke onset, because entrainment of the human circadian clock within hours is unlikely.

Daylight saving time transitions and hospital treatments due to accidents or manic episodes

BackgroundDaylight saving time affects millions of people annually but its impacts are still widely unknown. Sleep deprivation and the change of circadian rhythm can trigger mental illness and cause higher accident rates. Transitions into and out of daylight saving time changes the circadian rhythm and may cause sleep deprivation. Thus it seems plausible that the prevalence of accidents and/or manic episodes may be higher after transition into and out of daylight saving time. The aim of this study was to explore the effects of transitions into and out of daylight saving time on the incidence of accidents and manic episodes in the Finnish population during the years of 1987 to 2003.MethodsThe nationwide data were derived from the Finnish Hospital Discharge Register. From the register we obtained the information about the hospital-treated accidents and manic episodes during two weeks before and two weeks after the transitions in 1987–2003.ResultsThe results were negative, as the transitions into or out of daylight saving time had no significant effect on the incidence of accidents or manic episodes.ConclusionOne-hour transitions do not increase the incidence of manic episodes or accidents which require hospital treatment.

The role of ambient light level in fatal crashes: inferences from daylight saving time transitions

The purpose of this study was to estimate the size of the influence of ambient light level on fatal pedestrian and vehicle crashes in three scenarios. The scenarios were: fatal pedestrian crashes at intersections, fatal pedestrian crashes on dark rural roads, and fatal single-vehicle run-off-road crashes on dark, curved roads. Each scenario's sensitivity to light level was evaluated by comparing the number of fatal crashes across changes to and from daylight saving time, within daily time periods in which an abrupt change in light level occurs relative to official clock time. The analyses included 11 years of fatal crashes in the United States, between 1987 and 1997. Scenarios involving pedestrians were most sensitive to light level, in some cases showing up to seven times more risk at night over daytime. In contrast, single-vehicle run-off-road crashes showed little difference between light and dark time periods, suggesting factors other than light level play the dominant role in these crashes. These results are discussed in the context of the possible safety improvements offered by new developments in adaptive vehicle headlighting.

The influence of daylight saving time on motor vehicle fatal traffic accidents

This paper shows that Daylight Saving Time (DST) reduces fatal traffic accidents involving motor vehicles by approximately one percent, during several weeks at the spring and fall DST transitions. There is also a net reduction of about 0.7% during the DST period, March and April 1974, compared to the non-DST period, March and April 1973. However, there is little net DST effect on fatal accidents in the winter. The basic method employed to obtain this estimate of the effect of DST on motor vehicle accidents is to compare numbers of persons killed (fatalities) in these accidents during both DST and non-DST periods. This is accomplished by identifying high frequencies in the Fourier spectrum of traffic fatalities which are relatively sensitive to DST, and then using a bandpass filter to remove low frequency components not associated with DST. A cause/effect relationship between DST and fatal traffic accidents is then established by measuring changes in the filtered time series of fatality data across DST transitions, and across non-DST or control transitions. Certain statistical criteria are then applied to these measurements in order to confirm the existence of a DST effect on fatal traffic accidents and resulting fatalities.