Evening chronotype, late weekend sleep times and social jetlag as possible causes of sleep curtailment after maintaining perennial DST: ain’t they as black as they are painted?

Chronotype predicts working memory-dependent regional cerebral oxygenation under conditions of normal sleep and following a single night of sleep extension

The aim of this study was to test the hypothesis that the association between sleep duration and brain activation as assessed by regional cerebral oxygenation using near-infrared spectroscopy (NIRS) is dependent on chronotype. Sleep was tracked across two weeks by actigraphy in 22 adults instructed to keep their normal sleep behavior. Chronotype was assessed by the midpoint of sleep on free days corrected for sleep debt on workdays (MSFsc). Prefrontal cerebral oxygenation (ΔHbDiff) during a visuospatial working memory task was measured in the morning after a night of normal sleep and after one night of extended sleep. Sleep extension was included to experimentally test the robustness of the association between sleep duration and ΔHbDiff. Habitual sleep duration (r = 0.43, p = 0.04) and MSFsc (r = - 0.66, p < 0.001) were significantly correlated with ΔHbDiff. After adjusting for MSFsc the relationship between sleep duration and ΔHbDiff was reduced to nonsignificant levels (r = 0.34, p = 0.11), while adjusting for sleep duration did not change the significant relationship between MSFsc and ΔHbDiff (r = - 0.62, p = 0.001). One night of sleep extension increased sleep duration by 140 min, on average, but no change in ΔHbDiff was observed. Dividing participants into earlier and later chronotypes revealed greater ΔHbDiff responses in earlier chronotypes that persisted after the night of sleep extension (mean ΔHbDiff difference = 1.35 μM, t = 2.87, p = 0.006, Hedges' g = 0.89). These results find chronotype to predict regional cerebral oxygenation responses during working memory processing under conditions of normal sleep and following a single night of sleep extension.

Evening chronotype, insufficient weekday sleep, and weekday-weekend gap in sleep times: What is really to blame for a reduction in self-perceived health among university students?

The association of insufficient sleep with reduced self-perceived health was previously well established. Moreover, it was sometimes shown that the indicators of poorer health were significantly related to chronotype and weekday-weekend gaps in sleep timing and duration. It remains to be elucidated, however, whether chronotype and these gaps can contribute to the reduced health self-ratings independently from shortened sleep duration or, alternatively, their relationship with health can be simply explained by their association with insufficient sleep on weekdays. In an online survey, we tested whether the self-rated health of university students can be predicted by several individual characteristics of the sleep-wake cycles, such as chronotype, weekday and weekend sleep times, weekday-weekend gap in sleep times, sleepability and wakeability at different times of the day, etc. Responses to a question about general health and to items of several questionnaires for chronobiological assessment were collected from smartphones of 1582 university students (mean age ± standard deviation was 19.5 ± 1.7 y). The results of regression analyses suggested that lower odds of having good self-rated health were significantly associated with an earlier weekday risetime, a later weekday bedtime, and, consequently, a shorter weekday time in bed. After accounting for weekday sleep, self-rated health showed significant association with neither chronotype nor weekday-weekend differences in sleep duration and timing. Besides, the adverse health effects of reduced weekday sleep were independent from the significant adverse effects of several other individual sleep-wake characteristics including poorer nighttime sleepability and lower daytime wakeability. We concluded that university students perceive the negative health impacts of losing sleep by waking up early on weekdays irrespective of their night sleep quality and daytime level of alertness. Their chronotype and weekday-weekend difference in sleep times might not be among significant contributors to this perception. It is of practical importance to consider the reduction of weekday sleep losses among the interventions aimed at preventing sleep and health problems.

Association between chronotype, sleep pattern, and eating behaviours in a group of Italian adults

A cross-sectional study was conducted to assess the possible relationship between chronotype, sleeping, and eating patterns in 74 Italian adults (71.6% women). Based on Morningness-Eveningness Questionnare (MEQ) score, participants were classified as morning (n = 24), intermediate (n = 25), and evening (n = 25) chronotypes. From analysis, no significant differences among chronotypes emerged for sleep habits. As to eating behaviours, the evening subjects showed a significant (p < 0.05) shift towards later hours of the day in the consumption of all meals, except dinner. In addition, the evening subjects had a later midpoint of energy intake (EI) of about 35 min and 1 h (p < 0.001), respectively, than the intermediate and morning subjects. Analysing the diet quality, morning subjects reported significantly (p = 0.030) lower consumption of sweets and sweeteners, and significantly (p = 0.035) lower intake of ultra-processed fats and seasonings. Evening subjects showed a significant delay in EI during the day, while morning subjects reported a better-quality diet.

Weekend sleep after early and later school start times confirmed a model-predicted failure to catch up sleep missed on weekdays

Background

Many people believe they sleep for longer time on weekend nights to make up for sleep lost on weekdays. However, results of simulations of risetimes and bedtimes on weekdays and weekends with a sleep–wake regulating model revealed their inability to prolong weekend sleep. In particular, they predicted identical durations of weekend sleep after weeks with relatively earlier and relatively later risetime on weekdays. In the present study, this paradoxical prediction was empirically confirmed.

Methods

Times in bed were calculated from weekday and weekend risetimes and bedtimes in pairs of samples of students with early and later school start time and in subsets of samples from 7 age groups with weekday risetime earlier and later than 7:00 a.m.

Results

Among 35 pairs of students, mean age ± standard deviation was 14.5 ± 2.9 years and among the age group samples, 21.6 ± 14.6 years. As predicted by the simulations, times in bed on weekends were practically identical in the samples with early and later school start time and in two subsets with earlier and later weekday risetime.

Conclusions

The model-based simulations of sleep times can inform an individual about an amount of irrecoverable loss of sleep caused by an advance shift of wakeups on weekdays.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11325-022-02648-5.

Sleep during "lockdown" highlighted the need to rethink the concept of weekend catch-up sleep

Purpose

Many people believe in their ability to sleep for longer time on weekends to make up for sleep lost due to early wakeups on weekdays. This widely held belief was not supported by the simulations of rise- and bedtimes on weekdays and weekends with a sleep–wake regulating model. The simulations suggested the inability to extend sleep on any of two weekend nights and they predicted identical weekend sleep durations for weeks with relatively earlier and relatively later weekday risetimes. By April 2020, about half of the world’s population was under some form of “lockdown” due to the COVID-19 pandemic. This “lockdown” provided a new opportunity to demonstrate the predictive power of the sleep–wake regulating models. Therefore, the purpose of this report was to support the prediction of identity of weekend sleep durations after weeks with earlier and later weekday wakeups.

Methods

Weekend and weekday rise- and bedtimes before and during “lockdown” for 31 samples were taken from recent journal publications. Time in bed on weekends and 12 other measures of sleep duration and timing were calculated and simulated.

Results

For only one of 13 measures, weekend time in bed, statistical analysis did not yield a statistically significant difference between the estimates obtained before and during “lockdown”. The model-based simulations pointed to the 0.3-h delay of the sleep–wake cycle in response to the 1-h delay of weekday risetime during “lockdown”.

Conclusion

The model-based prediction was confirmed, thus, highlighting again the necessity to rethink the concept of weekend catch-up sleep.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11325-021-02492-z.

Acute Myocardial Infarction and Daylight Saving Time Transitions: Is There a Risk?

Available evidence on the risk of acute myocardial infarction (AMI) in the days after the spring daylight saving time (DST) transition suggests either a modest increase or no risk increase. Partial sleep deprivation and enhanced circadian clock misalignment have been implicated as the underlying mechanisms for increased AMI risk, probably via enhanced thrombo-inflammatory processes and activation of the sympathetic nervous system. Most of the studies, as we suggest as a perspective here, have used potentially inappropriate control periods, including the two post-transitional weeks, because adjustment after the spring DST transition lasts at least four weeks for all chronotypes and probably even beyond this period for late chronotypes. The most plausible conclusions, at the moment, for the risk of AMI after the spring DST transition are: (1) the risk is increased, (2) a relatively modest risk increase could be currently underestimated or in some studies undetected, (3) late chronotypes and/or individuals with high levels of social jetlag (a proxy for circadian clock misalignment) could be more affected by the phenomenon, and (4) underlying pathophysiological mechanisms should be further explored. As a significant part of world’s population continues to be affected by the biannual clock change, the question of increased AMI risk in the post-transitional period remains an intriguing public health issue.

Marathon run performance on daylight savings time transition days: results from a natural experiment

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.

Chronobiological traits predict the restrained, uncontrolled, and emotional eating behaviors of female university students

Although significant associations between diurnal preference and restrained eating behaviors were previously reported, such reports are scarce and, in some respects, inconclusive. In this cross-sectional survey of 567 female university students aged between 17 and 23 years, we tried to clarify and extend the previous findings on chronobiological correlates of these behaviors. We administered the three-Factor-Eating-Questionnaire Revised and three questionnaires designed to assess trait-, ability-, and state-like differences in the domain of chronobiology, the Morningness-Eveningness Questionnaire (MEQ), the Sleep-Wake Pattern Assessment Questionnaire, and the Munich ChronoType Questionnaire, respectively. Statistical analyses included factor, correlation, and regression analyses. We found that any of three aspects of unhealthy eating behaviors (i.e., lack of cognitive eating restraint, uncontrolled eating, and emotional eating) was linked to one or more dimensions of individual chronobiological differences. We explained the previously reported inconclusive results by the differential relationship of two subconstructs of diurnal preferences to eating behaviors. For instance, such relationship was found for two (morning and evening) subscales of the MEQ. Cognitive eating restraint and uncontrolled eating were related to the morning subscale, while emotional eating was related to the evening subscale. These associations were supported by the associations revealed for morning vs. evening components of earliness-lateness assessed with two other questionnaires, (e.g., morning lateness and sleep offset vs. evening lateness and sleep onset, respectively). We conclude that unhealthy eating behaviors seem to be linked to unhealthy sleep-wake habits and behaviors and to inabilities to wake or sleep on demand at certain times of the day.

Differences between male and female university students in sleepiness, weekday sleep loss, and weekend sleep duration

INTRODUCTION

Women and men experience sleep differently and the difference in intrinsic desire for sleep might underlie some of the observed male-female differences. The objective of this cross-sectional questionnaire study of university students was to determine male-female differences in self-reported sleepiness and sleep-wake patterns.

METHODS

Five questionnaires were completed by 1650 students at four Russian universities.

RESULTS

Compared to male students, female students reported a lower subjective sleep quality score, had a higher morning sleepability score and lower nighttime and daytime wakeability scores. They more often reported excessive daytime sleepiness and expected to be sleepier at any time of the day with the largest male-female difference around the times of sleep onset and offset. On free days, they reported a longer sleep duration and an earlier sleep onset. Free-weekday difference was larger for sleep duration and smaller for sleep onset. Such male-female differences showed similarity to the differences observed in university and high school students from different countries around the globe. There was no significant male-female difference in weekly averaged sleep duration, weekday sleep duration, hours slept, midpoint of sleep on free days, free-weekday difference in sleep offset, social jetlag, and morningness-eveningness score. Therefore, when studies rely on these self-reports, the most salient male-female differences might not be immediately evident.

CONCLUSIONS

It seems that the intrinsic desire for longer sleep duration might contribute to a higher susceptibility of female students to weekday sleep loss. Among these students, negative effects of reduced sleep duration might be more common and more detrimental.