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Individual response to the end of Daylight Saving Time is largely dependent on habitual sleep duration
Abstract
The end of Daylight Saving Time provides a valuable opportunity to study the effects of a small, 1-h shift in local clock time in a naturalistic setting. Previous research suggests a delay in adjusting activity patterns by at least one week, possibly more. This study was designed to investigate the importance of prior sleep habits in predicting adaptation to the new schedule. One hundred and twenty participants completed the Pittsburgh Sleep Diary for six days before and six days after the October, UK transition (2010). A subsample (n = 35) also wore activity watches throughout the study. Adherence to the external clock by adjusting bed times and rise times was apparent on the first night, but difficulties in following this timing on subsequent nights, along with deterioration in sleep latency and efficiency, point to a delay in full adjustment, particularly for those who habitually sleep for less than 7.5 h/night.
... The relationship between DST and traffic accidents has also been studied with inconsistent conclusions [22][23][24][25][26][27], and, although few studies address this issue, no effects of DST on psychiatric disorders have been found [28,29], with the exception of an increase in suicides in vulnerable males [30]. However, a few studies have focused on the effects of DST and ST transitions on sleep, finding a resynchronization of waking times and bedtimes after five days [31,32] and after one week [33], with a reduction in the duration and quality of sleep [32,[34][35][36][37][38][39], and alterations in sleep onset and offset after the transition to DST [9,[40][41][42]. Regarding the shift back to ST, the results are inconclusive as a better adjustment to this transition [42], no change at all in sleep [43,44], compromised sleep (especially for morning chronotypes) [36], beneficial effects on sleep quality [33], and increased sleep duration [37,41] have been reported. ...
... The relationship between DST and traffic accidents has also been studied with inconsistent conclusions [22][23][24][25][26][27], and, although few studies address this issue, no effects of DST on psychiatric disorders have been found [28,29], with the exception of an increase in suicides in vulnerable males [30]. However, a few studies have focused on the effects of DST and ST transitions on sleep, finding a resynchronization of waking times and bedtimes after five days [31,32] and after one week [33], with a reduction in the duration and quality of sleep [32,[34][35][36][37][38][39], and alterations in sleep onset and offset after the transition to DST [9,[40][41][42]. Regarding the shift back to ST, the results are inconclusive as a better adjustment to this transition [42], no change at all in sleep [43,44], compromised sleep (especially for morning chronotypes) [36], beneficial effects on sleep quality [33], and increased sleep duration [37,41] have been reported. ...
... According to previous studies [31,33] and to our results, this assumption seems to be true, since TM5 for wrist temperature tended to occur later after transitioning back to ST and earlier when changing to DST. Interestingly, although we have not controlled for prior sleep duration, Harrison (2012) [32] pointed out that those participants with prior sleep durations shorter than 7.5 h find it more difficult to fully adjust to ST after DST. ...
Several studies have investigated the relationship between daylight saving time (DST) and sleep alterations, psychiatric disorders, cardiovascular events and traffic accidents. However, very few have monitored participants while maintaining their usual lifestyle before and after DST. Considering that DST transitions modify human behavior and, therefore, people’s light exposure patterns, the aim of this study was to investigate the potential effects of DST on circadian variables, considering sleep and, for the first time, the human phase response curve to light. To accomplish this, eight healthy adults (33 ± 11 years old, mean ± SD) were recruited to monitor multivariable circadian markers and light exposure by means of a wearable ambulatory monitoring device: Kronowise®. The following night phase markers were calculated: midpoints of the five consecutive hours of maximum wrist temperature (TM5) and the five consecutive hours of minimum time in movement (TL5), sleep onset and offset, as well as sleep duration and light intensity. TM5 for wrist temperature was set as circadian time 0 h, and the balance between advances and delays considering the phase response curve to light was calculated individually before and after both DST transitions. To assess internal desynchronization, the possible shift in TM5 for wrist temperature and TL5 for time in movement were compared. Our results indicate that the transition to DST seems to force the circadian system to produce a phase advance to adapt to the new time. However, the synchronizing signals provided by natural and personal light exposure are not in line with such an advance, which results in internal desynchronization and the need for longer synchronization times. On the contrary, the transition back to ST, which implies a phase delay, is characterized by a faster adaptation and maintenance of internal synchronization, despite the fact that exposure to natural light would favor a phase advance. Considering the pilot nature of this study, further research is needed with higher sample sizes.
... Potential modifiers of the effect of the clock changes on sleep duration include chronotype (morning/evening preference) and habitual sleep duration. The Spring change is thought to have the most detrimental effect on the sleep duration of evening types and short sleepers (< 8 hr), whilst morning types and long sleepers (> 8 hr) lose the most sleep in Autumn (Harrison, 2013b;Kantermann et al., 2007;Lahti et al., 2006b;Lahti et al., 2008;Tyler et al., 2021). In addition, the negative impact of the Spring clock change on sleep efficiency (proportion of time in bed spent asleep) has been found to be more pronounced in those with a prior sleep debt (not meeting your preferred sleep duration) in the week before the clock change (Lahti et al., 2006a). ...
We explored the effects of daylight saving time clock changes on sleep duration in a large accelerometer dataset. Our sample included UK Biobank participants ( n = 11,780; aged 43–78 years) with accelerometer data for one or more days during the 2 weeks surrounding the Spring and Autumn daylight saving time transitions from October 2013 and November 2015. Between‐individual t ‐tests compared sleep duration on the Sunday (midnight to midnight) of the clock changes with the Sunday before and the Sunday after. We also compared sleep duration on all other days (Monday–Saturday) before and after the clock changes. In Spring, mean sleep duration was 65 min lower on the Sunday of the clock changes than the Sunday before (95% confidence interval −72 to −58 min), and 61 min lower than the Sunday after (95% confidence interval −69 to −53). In Autumn, the mean sleep duration on the Sunday of the clock changes was 33 min higher than the Sunday before (95% confidence interval 27–39 min), and 38 min higher than the Sunday after (95% confidence interval 32–43 min). There was some evidence of catch‐up sleep after both transitions, with sleep duration a little higher on the Monday–Friday than before, although this was less pronounced in Autumn. Future research should use large datasets with longer periods of accelerometer wear to capture sleep duration before and after the transition in the same individuals, and examine other aspects of sleep such as circadian misalignment, sleep fragmentation or daytime napping.
... Potential modifiers of the effect of the clock changes on sleep duration include chronotype (morning/evening preference) and habitual sleep duration. The Spring change is thought to have the most detrimental effect on the sleep duration of evening types and short sleepers (< 8 hr), whilst morning types and long sleepers (> 8 hr) lose the most sleep in Autumn (Harrison, 2013b;Kantermann et al., 2007;Lahti et al., 2006b;Lahti et al., 2008;Tyler et al., 2021). In addition, the negative impact of the Spring clock change on sleep efficiency (proportion of time in bed spent asleep) has been found to be more pronounced in those with a prior sleep debt (not meeting your preferred sleep duration) in the week before the clock change (Lahti et al., 2006a). ...
Background
Daylight saving time (DST) clock changes have been associated with sleep loss for around a week after the transitions. This is thought to contribute to an increase in the number of heart attacks, strokes, depressive episodes and fatal traffic accidents after the clock changes. However, most studies of DST clock changes on sleep have relied on subjective self-report data, which may be affected by recall bias. Furthermore, estimates from more objective, accelerometer-measured sleep studies have lacked precision due to small sample sizes. We aimed to explore the effects of DST clock changes on sleep duration in a large accelerometer dataset.
Methods
UK Biobank participants (n= 3,130; aged 43-77) wore accelerometers for 6 days over Spring and Autumn DST transitions between October 2013 and 2015. Paired t-tests compared people’s sleep on days before and after the clock changes, and on the Saturday and Sunday of the clock change. Linear regression analyses compared weekdays before and after the transitions. Analyses were stratified by sociodemographic characteristics. Results were compared to the normal weekend immediately prior to the clock changes.
Results
In Spring, mean daily sleep duration was 20 minutes shorter (95%CI -25 to -15) on days after the clock change than before (normal weekend: 10 minutes longer). On the Sunday of the clock change sleep duration was 54 minutes shorter (95%CI -60 to -47) than on the Saturday (normal weekend: 20 minutes longer). Sleep duration was 18 minutes longer on the Wednesday after the clock change than the Wednesday before the change (95%CI 4 to 31) (normal weekend: no weekday differences). In Autumn, mean daily sleep duration was 37 minutes longer (95%CI 33 to 40) on days after the clock change than before (normal weekend: 15 minutes longer). Sleep duration on the Sunday of the clock change was 60 minutes longer (95%CI 56 to 65) than on the Saturday (normal weekend: 25 minutes longer). There were no detectable differences in sleep duration between the weekdays before and after the Autumn transition.
Conclusion
Using a large accelerometer dataset we found that the Spring DST transition is associated with a reduction in sleep duration, whilst the Autumn clock change is associated with an increase in sleep duration. In contrast to previous research, the effect of both transitions on sleep duration was short-lived. Future research should explore ways to minimise the acute sleep loss experienced over the Spring clock change to reduce adverse health effects.
... Potential modifiers of the effect of the clock changes on sleep duration include chronotype (morning/evening preference) and habitual sleep duration. The Spring change is thought to have the most detrimental effect on the sleep duration of evening types and short sleepers (<8 hours), whilst morning types and long sleepers (>8 hours) lose the most sleep in Autumn [21][22][23][24][25] . Studies also indicate that those not meeting their preferred sleep duration the week before the clock change are most disrupted by both changes 16 . . ...
We explored the effects of daylight saving time (DST) clock changes on sleep duration in a large accelerometer dataset. Our sample included UK Biobank participants (n= 11,780; aged 43-78) with accelerometer data for one or more days during the two weeks surrounding the Spring and Autumn DST transitions from October 2013 and November 2015. Between-individual t-tests compared sleep duration on the Sunday (midnight to midnight) of the clock changes to the Sunday before and the Sunday after. We also compared sleep duration on all other days (Monday-Saturday) before and after the clock changes. In Spring, mean sleep duration was 65 minutes lower on the Sunday of the clock changes than the Sunday before (95%CI -72 to -58 minutes) and 61 minutes lower than the Sunday after (95%CI -69 to -53). In Autumn, the mean sleep duration on the Sunday of the clock changes was 33 minutes higher than the Sunday before (95% CI 27 to 39 minutes) and 38 minutes higher than the Sunday after (95% CI 32 to 43 minutes). There was some evidence of catch-up sleep after both transitions, with sleep duration a little higher on the Monday - Friday than before, although this was less pronounced in Autumn. Future research should use large datasets with longer periods of accelerometer wear to capture sleep duration before and after the transition in the same individuals, and examine other aspects of sleep such as circadian misalignment, sleep fragmentation or daytime napping.
... To the best of our knowledge, our study is the first to examine whether DST adjustments influence investors' processing of firm-specific accounting disclosures. 6 Michelson (2011) finds that DST delays lead to an increase in sleep duration, whereas Harrison (2013b) finds that fall DST delays result in increased sleep duration for habitual short sleepers but reduced sleep duration for habitual long sleepers. Barnes and Wagner (2009) fail to find evidence of changes in sleep patterns following fall DST delays. ...
Although daylight saving time (DST) is thought to provide economic benefits, extant research documents various adverse effects of DST adjustments. However, prior research provides little conclusive evidence about the effects of DST adjustments on capital market participants. We examine the effects of “spring forward” DST advances, which disrupt the human sleep cycle and economic activities, on investors’ processing of earnings news. We find a delayed price response to earnings news released during the first week following a DST advance. We also find that this effect is stronger among firms with investors who are more likely to be trading on earnings news and among firms with less sophisticated investors. Our findings contribute to research on the unintended consequences of DST adjustments and to the growing literature on intra-investor variation in disclosure processing costs. Our study may be of interest to legislators currently debating proposed legislation that would eliminate DST phasing.
Data Availability: Data are available from the sources cited in the text.
JEL Classifications: D83; G14; M41; M48.
... For each donation, the following information was calculated and used in the statistical analyses: the day of the week/month/year of the donation and the time of day the donation was made. In accordance with prior reports [41,43,63,120,121], analysis focused on the weekdays following the transition, as both the ST and DST transitions result in sleep consequences lasting up to 5 days before sleep onset and offset times revert, and habitual sleep patterns return [59,122]. Analyses therefore focused on a robust window that spanned multiple days of assessment (see Note D in S1 Text for a secondary analysis focusing on posttransition Monday alone). ...
Humans help each other. This fundamental feature of homo sapiens has been one of the most powerful forces sculpting the advent of modern civilizations. But what determines whether humans choose to help one another? Across 3 replicating studies, here, we demonstrate that sleep loss represents one previously unrecognized factor dictating whether humans choose to help each other, observed at 3 different scales (within individuals, across individuals, and across societies). First, at an individual level, 1 night of sleep loss triggers the withdrawal of help from one individual to another. Moreover, fMRI findings revealed that the withdrawal of human helping is associated with deactivation of key nodes within the social cognition brain network that facilitates prosociality. Second, at a group level, ecological night-to-night reductions in sleep across several nights predict corresponding next-day reductions in the choice to help others during day-to-day interactions. Third, at a large-scale national level, we demonstrate that 1 h of lost sleep opportunity, inflicted by the transition to Daylight Saving Time, reduces real-world altruistic helping through the act of donation giving, established through the analysis of over 3 million charitable donations. Therefore, inadequate sleep represents a significant influential force determining whether humans choose to help one another, observable across micro- and macroscopic levels of civilized interaction. The implications of this effect may be non-trivial when considering the essentiality of human helping in the maintenance of cooperative, civil society, combined with the reported decline in sufficient sleep in many first-world nations.
... It is worth noting duration at all time points fell below recommended levels of sleep per night of 7 or more hours [13]. The immediate one-hour shift in clock time requires an adjustment period for our internal biological clocks to reset to the new timing of daylight hours, accounting for the immediate disruptions to sleep duration [49]. It is likely the observed changes in sleep duration return to pretransition levels in following weeks, however further research for longer periods is needed to examine this. ...
Background
Time spent in daily activities (sleep, sedentary behaviour and physical activity) has important consequences for health and wellbeing. The amount of time spent varies from day to day, yet little is known about the temporal nature of daily activity patterns in adults. The aim of this review is to identify the annual rhythms of daily activity behaviours in healthy adults and explore what temporal factors appear to influence these rhythms.
Methods
Six online databases were searched for cohort studies exploring within-year temporal patterns (e.g. season effects, vacation, cultural festivals) in sleep, sedentary behaviour or physical activity in healthy 18 to 65-year-old adults. Screening, data extraction, and risk of bias scoring were performed in duplicate. Extracted data was presented as mean daily minutes of each activity type, with transformations performed as needed. Where possible, meta-analyses were performed using random effect models to calculate standardised mean differences (SMD).
Results
Of the 7009 articles identified, 17 studies were included. Studies were published between 2003 and 2019, representing 14 countries and 1951 participants, addressing variation in daily activities across season ( n = 11), Ramadan ( n = 4), vacation ( n = 1) and daylight savings time transitions ( n = 1). Meta-analyses suggested evidence of seasonal variation in activity patterns, with sleep highest in autumn (+ 12 min); sedentary behaviour highest in winter (+ 19 min); light physical activity highest in summer (+ 19 min); and moderate-to-vigorous physical activity highest in summer (+ 2 min) when compared to the yearly mean. These trends were significant for light physical activity in winter (SMD = − 0.03, 95% CI − 0.58 to − 0.01, P = 0.04). Sleep appeared 64 min less during, compared to outside Ramadan (non-significant). Narrative analyses for the impact of vacation and daylight savings suggested that light physical activity is higher during vacation and that sleep increases after the spring daylight savings transition, and decreases after the autumn transition.
Conclusions
Research into temporal patterns in activity behaviours is scarce. Existing evidence suggests that seasonal changes and periodic changes to usual routine, such as observing religious events, may influence activity behaviours across the year. Further research measuring 24-h time use and exploring a wider variety of temporal factors is needed.
... For example, Barnes and Wagner (2009) find no significant increase in sleep duration after the fall DST, while Michelson (2011) finds that people sleep 40 more minutes on the night of clock change in the fall. Harrison (2013b) finds heterogeneous sleep effects, where habitual long sleepers experienced a reduction in sleep duration while habitual short sleepers experienced an increase in sleep duration after the fall DST. register, Janszky and Ljung (2008) and Janszky et al. (2012) find statistically elevated incidence ratios when comparing mean incidence rates of acute myocardial infarctions ("heart attacks") on the first seven days after spring DST to the incidence rates (on the same weekdays) two weeks before and two weeks after spring DST. ...
Chronic sleep deprivation is a significant and understudied public health issue. Using BRFSS survey data from the United States and an administrative census of 160 million hospital admissions from Germany, we study the causal relationship between sleep and health. Our empirical approach exploits the end of Daylight Saving Time in a quasi-experimental setting on a daily basis. First, we show that setting clocks back by one hour in the middle of the night significantly extends people’s sleep duration. In addition, we find significant health benefits via sharp reductions in hospital admissions. For example, hospitalizations due to cardiovascular diseases decrease by ten per day, per one million population. Using an event study approach, we find that the effects persists for four days after the time shift. Admissions due to heart attacks and injuries also exhibit the same characteristic four-day decrease. We also provide a series of checks to rule out alternative, non-sleep related, mechanisms. Finally, we discuss the benefits of additional sleep for the sleep-deprived as well as policy implications for nudging people to sleep more. Our findings illustrate the importance of public policies that target sleep deprivation.
... For example, Barnes and Wagner (2009) find no significant increase in sleep duration after the fall DST, while Michelson (2011) finds that people sleep 40 more minutes on the night of clock change in the fall. Harrison (2013b) finds heterogeneous sleep effects, where habitual long sleepers experienced a reduction in sleep duration while habitual short sleepers experienced an increase in sleep duration after the fall DST. register, Janszky and Ljung (2008) and Janszky et al. (2012) find statistically elevated incidence ratios when comparing mean incidence rates of acute myocardial infarctions ("heart attacks") on the first seven days after spring DST to the incidence rates (on the same weekdays) two weeks before and two weeks after spring DST. ...
Under the evidence that the Daylight Saving Time (DST) regime does not accomplish its primary goal of saving energy, I analyze one of the main side effects, automobile accidents in Chile between 2002 and 2018. I use a Regression Discontinuity Design (RDD) exploiting the discrete nature of the transition into DST and a Difference‐in‐Difference (DID) approach, taking advantage of the changes in dates that the policy starts and ends over the years. I find a 2.7% reduction in automobile accidents under the DST regime. I isolate the two main mechanisms: sleep disruption and the reallocation of light. I find suggestive evidence that the sleep disruption effect plays a relevant role at both transitions: it increases automobile accidents by 6% the first week following the transition into DST and decreases them by 3.9% the first week following the transition into Standard Time (ST). I also find evidence that ambient light reduces serious and fatal accident risk.
Background and Objectives
There has been conflicting evidence regarding the association between seasonal changes and daylight-savings time and sleep disorders. This topic is of current particular interest, as the United States and Canada are considering the elimination of seasonal clock changes. The aim of this study is to compare sleep symptoms among participants who were interviewed in different seasons, and before/after the transition into daylight saving time (DST) and standard time (ST).
Methods
30,097 people aged 45–85 years taking part in the Canadian Longitudinal Study on Aging (CLSA) were studied. Participants completed a questionnaire on sleep duration, satisfaction, sleep-onset insomnia, sleep-maintenance insomnia, and hypersomnolence symptoms. Sleep disorders were compared between participants who were interviewed during different seasons and at different times of the year (DST/ST). Data was analyzed using Chi Square, ANOVA, binary logistic, and linear regression tests.
Results
Among participants interviewed in different seasons, we found no difference in dissatisfaction with sleep, sleep-onset, sleep-maintenance, and hypersomnolence. Those interviewed in summer had slightly shorter sleep duration compared to winter (6.76±1.2 vs. 6.84±1.3 hours). Participants interviewed one week before versus one week after DST transition showed no difference in sleep symptoms, except for a 9-minute decrease in sleep duration a week after transition. However, those who were interviewed a week after transition to ST compared to a week before reported more dissatisfaction with sleep (28% vs. 22.6%, adjusted odds ratio [95%CI]=1.34 [1.02,1.76]), higher sleep-onset insomnia (7.1% vs. 3.3%, AOR=2.26 [1.19,4.27]), higher sleep-maintenance insomnia (12.9% vs. 8.2%, AOR=1.64 [1.02,2.66]), and more hypersomnolence with adequate sleep (7.3% vs. 3.6%, AOR=2.08 [1.14,3.79].
Discussion
We found small seasonal variations in sleep duration but no difference in other sleep symptoms. The transition from DST to ST was associated with a transient increase in sleep disorders.
Advancing clock times by 1 h in the spring to daylight savings time and setting clock times back 1 h in the autumn to standard time disrupts circadian timing, sleep and skilled motor behavior such as driving an automobile. It is unknown if endurance performance is impacted by daylight savings transition (DST). The natural experiment described here examined whether exposure to a DST in the 10 h prior to the start of a marathon race was associated with a different mean completion time compared to participants who ran the same course but were unexposed to a recent DST. The primary outcome was the average running time of finishers of United States marathons that were completed on either spring-DST or autumn-DST days in the years 2000-2018. Comparisons were made to results from the same marathon held in a different year that was not run on a DST day. Data were obtained from the public data base marathonguide.com/results. Analysis of the primary outcome used paired samples t-tests weighted by sample size. Spring and autumn data were analyzed separately. Eighteen spring and 29 autumn marathons met the inclusion criteria. Compared to control marathons, the weighted spring-DST performance was worse by 12.3 min (4.1%; P < .001) and equal to a moderate standardized effect size of 0.57 while autumn-DST was trivially worse by 1.4 min (0.5%), which was equivalent to an effect size of 0.13. Ambient temperatures for the DST and control races did not differ for either the spring (10.6 vs. 8.9℃; P = .212) or autumn marathons (7.6 vs. 9.3℃; P = .131). Within the limitations of a natural experiment research design, it is concluded that the findings support worse running performance in marathon races held in the spring on the day of transition to daylight savings time when there is a forced circadian change and sleep loss.
The original rationale for the adoption of daylight saving time (DST) was to conserve energy; however, the effects of DST on energy consumption are questionable or negligible. Conversely, there is substantial evidence that DST transitions have the cumulative effect on sleep deprivation with its adverse health effects. In light of current evidence, the European Commission in 2018 decided that biannual clock change in Europe would be abolished. Current indirect evidence supports the adoption of perennial standard time, which aligns best with the human circadian system and has the potential to produce benefits for public health and safety.
Diese Studie untersucht die energetischen und wohlfahrtsökonomischen Auswirkungen der Umstellung von „Winterzeit“ (= gemäß Definition „Normalzeit“) auf „Sommerzeit“ in Oberösterreich. Ziel dieser Arbeit ist die erstmalige Verknüpfung von Analysen von energetischen sowie von nicht-energetischen Auswirkungen der Zeitumstellung im Sinne einer wohlfahrtsökonomischen Gesamtanalyse. Diese Analyse wird anhand einer Monetarisierung für das Bundesland Oberösterreich realisiert. Der regionale aber auch der nationale Bezug der Arbeit stellt ein Novum dar, denn es existieren bis dato keine umfangreichen (und aktuellen) Analysen zu den gesamten Effekten der Zeitumstellung für Österreich oder für Oberösterreich. Vorhandene Studien und Arbeiten mit dem Fokus auf energetische Effekte sind für Mitteleuropa (mit Schwerpunkt auf Deutschland) bereits aus den vergangenen Jahrzehnten. Eine aktualisierte Aufbereitung vor allem der energetischen Auswirkungen im regionalisierten Kontext ist aufgrund von Strukturveränderungen am Energiesektor von immanenter Bedeutung, um zeitgemäße Aussagen zu den Effekten der Zeitumstellung treffen zu können. Den innovativen Kern dieser Studie bilden somit die Zusammenführung vorhandener Literatur in Kombination mit Quantifizierungen der energetischen und nicht-energetischen Auswirkungen der Zeitumstellungen im Frühjahr und Herbst speziell für Oberösterreich.
Daylight saving time is currently adopted in over 70 countries and imposes a twice yearly 1 h change in local clock time. Relative ease in adjustment of sleep patterns is assumed by the general population but this review suggests that the scientific data challenge a popular understanding of the clock change periods. The start of daylight saving time in the spring is thought to lead to the relatively inconsequential loss of 1 h of sleep on the night of the transition, but data suggests that increased sleep fragmentation and sleep latency present a cumulative effect of sleep loss, at least across the following week, perhaps longer. The autumn transition is often popularised as a gain of 1 h of sleep but there is little evidence of extra sleep on that night. The cumulative effect of five consecutive days of earlier rise times following the autumn change again suggests a net loss of sleep across the week. Indirect evidence of an increase in traffic accident rates, and change in health and regulatory behaviours which may be related to sleep disruption suggest that adjustment to daylight saving time is neither immediate nor without consequence.
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.
The authors examine the differential influence of time changes associated with Daylight Saving Time on sleep quantity and associated workplace injuries. In Study 1, the authors used a National Institute for Occupational Safety and Health database of mining injuries for the years 1983-2006, and they found that in comparison with other days, on Mondays directly following the switch to Daylight Saving Time-in which 1 hr is lost-workers sustain more workplace injuries and injuries of greater severity. In Study 2, the authors used a Bureau of Labor Statistics database of time use for the years 2003-2006, and they found indirect evidence for the mediating role of sleep in the Daylight Saving Time-injuries relationship, showing that on Mondays directly following the switch to Daylight Saving Time, workers sleep on average 40 min less than on other days. On Mondays directly following the switch to Standard Time-in which 1 hr is gained-there are no significant differences in sleep, injury quantity, or injury severity.
A GREAT deal of attention has recently been paid to the circadian rhythms that have been found to exist in a number of human physiological and behavioural processes. There are several ways in which such rhythms can be disrupted, and extensive studies have been made of the effects of prolonged isolation1, abnormal working hours2, and flight across several time zones3. The adoption of Daylight Saving Time (DST) is another possible cause of disruption, but seems to have been generally ignored in spite of the large number of people potentially affected. We have found that significant disruptions of behaviour occur during adaptation to the time change.
An English language self-assessment Morningness-Eveningness questionnaire is presented and evaluated against individual differences in the circadian vatiation of oral temperature. 48 subjects falling into Morning, Evening and Intermediate type categories regularly took their temperature. Circadian peak time were identified from the smoothed temperature curves of each subject. Results showed that Morning types and a significantly earlier peak time than Evening types and tended to have a higher daytime temperature and lower post peak temperature. The Intermediate type had temperatures between those of the other groups. Although no significant differences in sleep lengths were found between the three types, Morning types retired and arose significantly earlier than Evening types. Whilst these time significatly correlated with peak time, the questionnaire showed a higher peak time correlation. Although sleep habits are an important déterminant of peak time there are other contibutory factors, and these appear to be partly covered by the questionnaire. Although the questionnaire appears to be valid, further evaluation using a wider subject population is required.
On the hypothesis that sleepiness and alcohol interact to increase the risk of alcohol-related traffic fatalities, the percentages of alcohol-related fatal traffic crashes were assessed for the entire state of New Mexico for the years 1989-1992, for each of the seven days that preceded the changes to and from Daylight Savings Time and for each of the 14 days which followed the changes to and from Daylight Savings Time. Consistent with our hypothesis the percentage of alcohol-related fatal crashes increased significantly during the first seven days after these changes in Daylight Savings Time.
Daylight saving time is widely adopted. Little is known about its influence on the daily rest-activity cycles. We decided to explore the effects of transition into daylight saving time on the circadian rhythm of activity.
We monitored the rest-activity cycles with the use of wrist-worn accelerometer on a sample of ten healthy adults for ten days around the transition into summer time. Identical protocols were carried out on the same individuals in two consecutive years, yielding data on 200 person-days for analysis in this study.
There was no significant effect on the rest-activity cycle in the sample as a whole. Fragmentation of the rest-activity cycle was enhanced in a subgroup of persons having sleep for eight hours or less (P = 0.04) but reduced in those who preferred to sleep for more than eight hours per night (P = 0.05). The average level of motor activity was increased in persons having the morning preference for daily activity patterns (P = 0.01).
Transition into daylight saving time may have a disruptive effect on the rest-activity cycle in those healthy adults who are short-sleepers or more of the evening type.
The aim of this study was to analyze the effects of transition out of and into daylight saving time on the rest-activity cycles and sleep. Rest-activity cycles of nine healthy participants aged 20 to 40 years were measured around transitions out of and into daylight saving time on fall 2005 and spring 2006 respectively. Rest-activity cycles were measured using wrist-worn accelerometers. The participants filled in the Morningness-Eveningness and Seasonal Pattern Assessment Questionnaires before starting the study and kept a sleep diary during the study.
Fall transition was more disturbing for the more morning type and spring transition for the more evening type of persons. Individuals having a higher global seasonality score suffered more from the transitions.
Transitions out of and into daylight saving time enhanced night-time restlessness and thereby compromised the quality of sleep.
Prior literature suggests that Daylight Saving Time (DST) can both increase the risk of automobile crashes in the short run and decrease the risk of automobile crashes in the long run. We use 28 years (1976-2003) of automobile crash data from the United States, and exploit a natural experiment arising from a 1986 federal law that changed the time when states switched to DST to identify the short run and long run effects of DST on automobile crashes. Our findings suggest that (1) DST has no significant detrimental effect on automobile crashes in the short run; (2) DST significantly reduces automobile crashes in the long run with a 8-11% fall in crashes involving pedestrians, and a 6-10% fall in crashes for vehicular occupants in the weeks after the spring shift to DST.
Changes of schedules larger than 3 h, such as jet lag and shift work, require an adjustment period of several days to resynchronize the sleep-wake cycle and several weeks to resynchronize other circadian rhythms to the new schedule. Initial studies on adaptation to small changes of schedule (1-2 h) found that the sleep-wake cycle adapts to the new schedule in less than 48 h, and such modifications are generally not studied because they may be confounded by a potential masking effect. This article summarizes the few published studies on Daylight Saving Time (DST) and sleep during weekends, two examples of small changes in schedule. There are individual differences in adaptation to daylight saving time, while some persons adjust immediately; other persons require more than 2 weeks. During weekends, people tend to go to bed and wake up later, and to extend their sleep. Delay and extension of sleep depend on factors such as shift of work during weekdays and chronotype (morningness-eveningness). Both DST and sleep during weekends offer the opportunity to study adaptation of the sleep-wake cycle in recurrent, social conditions. Studying these phenomena is also relevant to some socioeconomic issues, like the reported increase of traffic accidents and complaints from the population during daylight saving time; or the possible decrease in productivity and absenteeism during the ‘Blue Monday’.
Large disruptions of chronobiological rhythms are documented as destabilizing individuals with bipolar disorder; however, the impact of small phase altering events is unclear. Australian suicide data from 1971 to 2001 were assessed to determine the impact on the number of suicides of a 1-h time shift due to daylight saving. The results confirm that male suicide rates rise in the weeks following the commencement of daylight saving, compared to the weeks following the return to eastern standard time and for the rest of the year. After adjusting for the season, prior to 1986 suicide rates in the weeks following the end of daylight saving remained significantly increased compared to the rest of autumn. This study suggests that small changes in chronobiological rhythms are potentially destabilizing in vulnerable individuals.
SUMMARY Increasingly, there is a need in both research and clinical practice to document and quantify sleep and waking behaviors in a comprehensive manner. The Pittsburgh Sleep Diary (PghSD) is an instrument with separate components to be completed at bedtime and waketime. Bedtime components relate to the events of the day preceding the sleep, waketime components to the sleep period just completed. Two-week PghSD data is presented from 234 different subjects, comprising 96 healthy young middle-aged controls, 37 older men, 44 older women, 29 young adult controls and 28 sleep disorders patients in order to demonstrate the usefulness, validity and reliability of various measures from the instrument. Comparisons are made with polysomnographic and actigraphic sleep measures, as well as personality and circadian type questionnaires. The instrument was shown to have sensitivity in detecting differences due to weekends, age, gender, personality and circadian type, and validity in agreeing with actigraphic estimates of sleep timing and quality. Over a 12–31 month delay, PghSD measures of both sleep timing and sleep quality showed correlations between 0.56 and 0.81 (n= 39, P < 0.001).
Sleep duration has figured into claims of two trends promoted recently as dysfunctional in the mass media. One is the observation
that the population at large is sleeping less than before. The second is that the annual change from Standard Time to Daylight
Savings (or summer) Time causes adverse effects, largely through the loss of an hour’s sleep. This paper relies on recent
Canadian and U.S. time-use data to empirically test both of these value-laden allegations. Analysis of Statistics Canada’s
general social surveys containing time-use information in 1986, 1992, 1998, and 2005 shows that the mean duration of sleep
was unchanged between 1986 and 1998 and actually declined by about 15min a night in 2005, reflecting an earlier bedtime and
unchanged arising time. Sleep duration is not constant in the population, though, and the media view might reflect the habits
of population sectors such as the intelligence with great access to the media. The American Time Use Study sample of 20,720
respondents in 2003 enabled the analysis of time-use before, on, and after the dates of semi-annual time changes that year.
These data showed that any sleep time “lost” in the spring-forward time change was insignificant and short-lived due to the
fact that it occurred on the night between Saturday and Sunday, when people typically sleep much longer than on weekdays.
While there are other time trade-offs observed after time changes, their explanation lies in other directions.
KeywordsSleep–Duration–Change–Erosion–Compression–Time-use–Daylight savings time
The principal reason for introducing (and extending) daylight saving time (DST) was, and still is, projected energy savings, particularly for electric lighting. This paper presents a literature review concerning the effects of DST on energy use. Simple estimates suggest a reduction in national electricity use of around 0.5%, as a result of residential lighting reduction. Several studies have demonstrated effects of this size based on more complex simulations or on measured data. However, there are just as many studies that suggest no effect, and some studies suggest overall energy penalties, particularly if gasoline consumption is accounted for. There is general consensus that DST does contribute to an evening reduction in peak demand for electricity, though this may be offset by an increase in the morning. Nevertheless, the basic patterns of energy use, and the energy efficiency of buildings and equipment have changed since many of these studies were conducted. Therefore, we recommend that future energy policy decisions regarding changes to DST be preceded by high-quality research based on detailed analysis of prevailing energy use, and behaviours and systems that affect energy use. This would be timely, given the extension to DST underway in North America in 2007.
To measure the impact of the introduction of daylight saving in Western Australia in December 2006 on when during the day adults engaged in physical activity.
In early December 2006, 1,300 Western Australian adults were telephoned and asked about how the introduction of daylight saving would influence when during the day they typically engaged in physical activity. At the end of the daylight saving period in March 2007, 1,083 of the baseline cohort agreed to answer questions relating to how daylight saving had affected when during the day they were physically active.
Almost half the cohort (45.5%) reported that daylight saving had affected when during the day they were physically active. During daylight saving fewer people exercised in the morning and more people exercised in the evening. When analysed at the individual level, 23% of the cohort ceased to exercise in the morning during daylight saving and 22% exercised in the evening only during daylight saving. In addition, to changes in when during the day people exercised, there was also an overall reduction in the average number of daily exercise sessions, with 8% not exercising at all during daylight saving.
The results suggest that the introduction of daylight saving, a relatively modest compulsory change to increase daylight by one hour had an impact on patterns of when during the day people were physically active.
The study results reinforce the value of focusing on policy as an effective means of supporting population behaviour change.
Individuals differ in their biological rhythms and preferences for time of day. Here, we looked at the transition into daylight saving time (DST) in adolescents. As adolescents tend to be evening types, one may expect that they suffer from a transition into DST.
To assess these changes, we measured daytime sleepiness and morningness-eveningness preference (CSM score) in adolescents.
Daytime sleepiness correlated with age and CSM score. Older pupils and evening types showed a higher sleepiness. Daytime sleepiness was higher after the transition until the third week after. Older pupils and pupils scoring higher on eveningness reported higher daytime sleepiness after the transition, suggesting that these pupils suffer most from the change. Using cut-off scores for larks and owls, we found that owls showed higher sleepiness than larks.
As one consequence, class and school performance tests should not take place in the first week(s) after the transition into DST.
Various aspects of adjustment to Daylight Saving Time (DST) changes were investigated using two Spring and two Autumn studies. After both Spring and Autumn DST changes, although adjustment of times of retiring and falling asleep appeared to be instantaneous, waking times took up to a week to adjust. Other analyses suggested that beneficial effects on mood on awakening and perceived sleep quality might appear for much of the week after an Autumn DST change, but predominantly detrimental effects on mood after a Spring one. Performance on a calculations test at 0830 h was significantly enhanced after an Autumn DST change, though this was probably due to the enhancement in mood resulting from the change, rather than to simple lack of adjustment of the performance rhythm. Examination of individual differences in DST adjustment produced results that were consistent with those from previous studies in the shift-work and jet-lag areas, confirming the usefulness of DST changes as a vehicle for studying general problems of adjustment to changes in schedule.
Increasingly, there is a need in both research and clinical practice to document and quantify sleep and waking behaviors in a comprehensive manner. The Pittsburgh Sleep Diary (PghSD) is an instrument with separate components to be completed at bedtime and waketime. Bedtime components relate to the events of the day preceding the sleep, waketime components to the sleep period just completed. Two-week PghSD data is presented from 234 different subjects, comprising 96 healthy young middle-aged controls, 37 older men, 44 older women, 29 young adult controls and 28 sleep disorders patients in order to demonstrate the usefulness, validity and reliability of various measures from the instrument. Comparisons are made with polysomnographic and actigraphic sleep measures, as well as personality and circadian type questionnaires. The instrument was shown to have sensitivity in detecting differences due to weekends, age, gender, personality and circadian type, and validity in agreeing with actigraphic estimates of sleep timing and quality. Over a 12-31 month delay, PghSD measures of both sleep timing and sleep quality showed correlations between 0.56 and 0.81 (n = 39, P < 0.001).
Daylight saving time (DST) is widely adopted. We explored the effects of transition to daylight saving time on sleep. With the use of wrist-worn accelerometers, we monitored the rest-activity cycles on a sample of 10 healthy adults for 10 days around the transition to summer time. Identical measurement protocols were carried out twice on the same individuals during the transitions in the years of 2003 and 2004, yielding data on 200 person-days for analysis. Both sleep duration and sleep efficiency were reduced after the transition both years. After the transition sleep time was shortened by 60.14min (P<0.01) and sleep efficiency was reduced by 10% (P<0.01) on average. Transition to daylight saving time appears to compromise the process of sleep by decreasing both sleep duration and sleep efficiency.
A quarter of the world's population is subjected to a 1 hr time change twice a year (daylight saving time, DST). This reflects a change in social clocks, not environmental ones (e.g., dawn). The impact of DST is poorly understood. Circadian clocks use daylight to synchronize (entrain) to the organism's environment. Entrainment is so exact that humans adjust to the east-west progression of dawn within a given time zone. In a large survey (n = 55,000), we show that the timing of sleep on free days follows the seasonal progression of dawn under standard time, but not under DST. In a second study, we analyzed the timing of sleep and activity for 8 weeks around each DST transition in 50 subjects who were chronotyped (analyzed for their individual phase of entrainment). Both parameters readily adjust to the release from DST in autumn but the timing of activity does not adjust to the DST imposition in spring, especially in late chronotypes. Our data indicate that the human circadian system does not adjust to DST and that its seasonal adaptation to the changing photoperiods is disrupted by the introduction of summer time. This disruption may extend to other aspects of seasonal biology in humans.
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.
Transition into daylight saving time influences the fragmentation of the rest-activity cycle Daylight Saving Time transitions and road traffic accidents
- Ta Lahti
- S Leppamaki
- S-M Ojanen
- J A Huakka
- J Lonnqvist
- T1 Partonen
- Ta Lahti
- E Nysten
- J Haukka
- P Sulander
- Partonen
):article 3. Lahti TA, Leppamaki S, Ojanen S-M, Huakka J, Tuulio-Henriksson A, Lonnqvist J, Partonen T. 2006b. Transition into daylight saving time influences the fragmentation of the rest-activity cycle. J Circadian Rhythms. 4:1. Lahti TA, Nysten E, Haukka J, Sulander P, Partonen T. 2010. Daylight Saving Time transitions and road traffic accidents. J Environ Pub Health. Article ID: 657167.
Spring forward or not? Doubts on whether daylight saving time really conserves energy
- Cq Choi
Choi CQ. 2009. Spring forward or not? Doubts on whether daylight saving time really conserves energy. Sci Am. 300(3):18–19.