Weekday-weekend Differences Research Articles

Self-Reported Weekend Temporal Eating Patterns of American Adults Differ From Weekday: National Health and Nutrition Examination Surveys: 2015–2020 Prepandemic

BackgroundWeekend–weekday differences in time of ingestive events may be implicated in adverse metabolic and health outcomes. However, little is known about the nature of weekend–weekday differences in temporal eating behaviors of the US adult population. ObjectiveThe study aimed to examine weekend–weekday differences in temporal and energy characteristics of ingestive events self-reported by American adults. DesignObservational; within-person comparative. Participants/SettingThe data were from the National Health and Nutrition Examination Surveys (NHANES) 2015–March 2020 (pre-pandemic) for ≥20-year-old adults who provided 1 weekday (M–Th) and 1 weekend (F, S, Su) 24-h dietary recall (n = 3564 men and 3823 women). Main Outcome MeasuresPrespecified primary temporal outcomes were recalled: time of ingestive events, and the duration of ingestive and fasting windows. Secondary outcomes included frequency and energy characteristics of ingestive events. Statistical Analysis PerformedGender-specific, survey-weighted, multiple linear regression models that accounted for complex survey design with dummy covariates for weekend/weekday, mode of recall administration (in-person on day 1 and telephone on day 2), and a respondent-specific fixed intercept. ResultsIn both men and women, the weekend recalled time of first ingestive event, breakfast, and lunch were later than weekday (P ≤ .0008); however, no statistically significant differences were observed in time of dinner and the last eating episode. The mean weekend ingestive window (interval between the time of first and last eating events of the day) was shorter by 24 minutes (95% confidence interval [CI], –32, –11) in men and 18 minutes (95% CI, –20, –15) in women, and the mean overnight fasting window was correspondingly longer (P ≤ .0001). No statistically significant differences were observed between weekend and weekday frequency of ingestive events. Energy density of weekend food selections reported by women, and of beverages by men, was found to be higher than weekday (P ≤ .002). ConclusionsWeekend ingestive patterns were characterized by later time of first ingestive event, breakfast, and lunch, and selection of higher-energy-density foods and beverages.

Revisiting day-of-week ozone patterns in an era of evolving US air quality

Abstract. Past work has shown that traffic patterns in the USA and resulting NOx emissions vary by day of week, with NOx emissions typically being higher on weekdays than weekends. This pattern of emissions leads to different levels of ozone on weekends versus weekdays and can be leveraged to understand how local ozone formation changes in response to NOx emission perturbations in different urban areas. Specifically, areas with lower NOx but higher ozone on the weekends (the weekend effect) can be characterized as NOx-saturated and areas with both lower NOx and ozone on weekends (the weekday effect) can be characterized as NOx-limited. In this analysis, we assess maximum daily 8 h average (MDA8) ozone weekend–weekday differences across 51 USA nonattainment areas using 18 years of observed and modeled data from 2002–2019, using the following two metrics: mean MDA8 ozone and percentage of days with MDA8 ozone > 70 ppb (parts per billion). In addition, we quantify the modeled and observed trends in these weekend–weekday differences across this period of substantial NOx emission reductions in the USA. The model assessment is carried out using U.S. Environmental Protection Agency (EPA)'s Air QUAlity TimE Series Project (EQUATES) Community Multiscale Air Quality (CMAQ) model dataset. We identify three types of MDA8 ozone trends occurring across the USA, namely transitioning chemical regime, disappearing weekday effect, and no trend. The transitioning chemical regime trend occurs in a subset of large urban areas that were NOx-saturated (i.e., volatile organic compound (VOC)-limited) at the beginning of the analysis period but transitioned to mixed chemical regimes or NOx-limited conditions by the end of the analysis period. Nine areas have strong transitioning chemical regime trends using both modeled and observed data and with both metrics indicating strong agreement that they are shifting to more NOx-limited conditions: Milwaukee, Houston, Phoenix, Denver, the Northern Wasatch Front, the Southern Wasatch Front, Las Vegas, Los Angeles – San Bernardino County, Los Angeles – South Coast, and San Diego. The disappearing weekday effect was identified for multiple rural and agricultural areas of California which were NOx-limited for the entire analysis period but appear to become less influenced by local day-of-week emission patterns in more recent years. Finally, we discuss a variety of reasons why there are no trends in certain areas including complex impacts of heterogeneous source mixes and stochastic impacts of meteorology. Overall, this assessment finds that the EQUATES modeling simulations indicate more NOx-saturated conditions than the observations but do a good job of capturing year-to-year changes in weekend–weekday MDA8 ozone patterns.

Comparison of weekday-weekend differences in factors associated with school-age child sleep duration in the US and Singapore

Comparison of weekday-weekend differences in factors associated with school-age child sleep duration in the US and Singapore

Improved Spatial Resolution in Modeling of Nitrogen Oxide Concentrations in the Los Angeles Basin.

The extent to which emission control technologies and policies have reduced anthropogenic NOx emissions from motor vehicles is large but uncertain. We evaluate a fuel-based emission inventory for southern California during the June 2021 period, coinciding with the Re-Evaluating the Chemistry of Air Pollutants in CAlifornia (RECAP-CA) field campaign. A modified version of the Fuel-based Inventory of Vehicle Emissions (FIVE) is presented, incorporating 1.3 km resolution gridding and a new light-/medium-duty diesel vehicle category. NOx concentrations and weekday-weekend differences were predicted using the WRF-Chem model and evaluated using satellite and aircraft observations. Model performance was similar on weekdays and weekends, indicating appropriate day-of-week scaling of NOx emissions and a reasonable distribution of emissions by sector. Large observed weekend decreases in NOx are mainly due to changes in on-road vehicle emissions. The inventory presented in this study suggests that on-road vehicles were responsible for 55-72% of the NOx emissions in the South Coast Air Basin, compared to the corresponding fraction (43%) in the planning inventory from the South Coast Air Quality Management District. This fuel-based inventory suggests on-road NOx emissions that are 1.5 ± 0.4, 2.8 ± 0.6, and 1.3 ± 0.7 times the reference EMFAC model estimates for on-road gasoline, light- and medium-duty diesel, and heavy-duty diesel, respectively.

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?

ABSTRACT 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.

From early birds to night owls: a longitudinal study of actigraphy-assessed sleep trajectories during the transition from pre- to early adolescence.

Pre- and early adolescence are believed to constitute periods of important age-related changes in sleep. However, much of the research on these presumed developmental changes has used cross-sectional data or subjective measures of sleep, limiting the quality of the evidence. In addition, little is known about the development of certain features of the sleep-wake cycle pertaining to regularity (e.g. weekend-weekday differences and intra-individual variability) or circadian rhythms (e.g. sleep midpoint). This study examined the sleep trajectories of 128 typically developing youth (69 girls) from ages 8 to 12 years on four sleep characteristics: sleep onset, sleep offset, total sleep time (TST), and sleep midpoint. For each of these characteristics, actigraphy-derived estimates of typical (i.e. mean) sleep and sleep regularity were obtained at each time point. Multilevel growth curves were modeled. Overall, the sleep-wake cycle significantly changed between 8 and 12 years. Mean sleep onset, offset and midpoint exhibited an ascending curvilinear growth pattern that shifted later with age, while mean TST decreased linearly. Weekend-weekday differences (social jetlag) for sleep offset and midpoint became more pronounced each year. Weekday TST was longer than weekend TST, though this difference became smaller over time. Finally, intra-individual variability increased over time for all sleep characteristics, with variability in TST ascending curvilinearly. Important between-person and sex differences were also observed. This study reveals the marked changes that occur in the sleep of typically developing pre- and early adolescents. We discuss the potential implications of these trajectories.

Weekend-weekday variations, sources, and secondary transformation potential of volatile organic compounds in urban Zhengzhou, China

Periodical changes of human activities cause weekend-weekday differences of volatile organic compounds (VOCs) and nitrogen oxides (NO + NO2 = NOx) emissions, which induce urban ozone (O3) pollution and secondary organic aerosol (SOA) in fine particulate (with aerodynamic diameters ≤2.5 μm; PM2.5). However, influences of weekend-weekday differences in primary emissions on the production of secondary pollutants remain unknown. The TROPOspheric Monitoring Instrument and surface observations are carried to simultaneously monitor VOCs, NO2, O3, and PM2.5 concentrations in urban Zhengzhou, China during the weekend and the weekday. Reductions in anthropogenic activities result in atmospheric VOCs and NO2 reductions during the weekend. The ratios of formaldehyde columns to NO2 columns during the weekend afternoon and the weekday afternoon (0.53 and 0.39, respectively) are less than 2.30, indicating the O3 formation under the VOC-limited regime. Lower total VOCs (TVOCs) mixing ratios but higher ratios of TVOCs mixing ratios to NO2 mixing ratios during the weekend afternoon perform faster photochemical O3 production. In contrast, higher TVOCs mixing ratios are responsible for higher SOA formation during the weekday. Based on the positive matrix factorization model and VOCs reactivities, solvent usage, vehicle exhaust, and industrial sources are majorly responsible for SOA (80.1%) and O3 (79.9%) formation potential. To reduce O3 concentrations during the weekend and SOA concentrations during the weekday collaboratively, solvent, vehicle, and industrial activities should be transformed from weekday to weekend.

Time to Play in Javanese Preschool Children-An Examination of Screen Time and Playtime before and during the COVID-19 Pandemic.

This comparative-descriptive multi-national research examined the screen time and playtime of preschool children aged 1-6 years before and during the COVID-19 pandemic. Parents reported on the play and screen habits of preschool-aged children on the weekday and weekends using a questionnaire on the lifestyle habits of their children. Results indicated a significant difference in screen time and playtime on the weekday and weekend before the pandemic (screen time: 1.91 ± 2.40 vs. 2.16 ± 2.60 h; playtime: 3.55 ± 2.49 vs. 4.11 ± 2.58 h, both p < 0.05), but during the COVID-19 pandemic, only the weekday-weekend difference in screen time was significantly different (screen time: 2.87 ± 3.15 vs. 3.26 ± 3.18 h, p < 0.05; playtime: 3.25 ± 3.41 vs. 3.48 ± 2.41, p > 0.05). Before- and during-COVID-19 comparisons showed that the average daily screen time increased by 150% from 2.04 h to 3.06 h (p < 0.05), while the average play time decreased by 12.3% (3.83 to 3.36 h, p < 0.05). Based upon international guidelines for movement behaviours of young children, special attention and actions are needed to manage the excessive daily screen time and preserve the average daily playtime of Javanese preschool children. These results present useful benchmarking data for parents, teachers, and health authorities to initiate ameliorative interventions to better balance children's screen time and playtime as Indonesia emerges from the COVID-19 pandemic to a COVID-19 endemic.

Agreement between actigraphy and sleep diaries: A 28-day real-time monitoring study among suicidal adolescents following acute psychiatric care

ObjectiveTo examine the agreement between, and adherence to, wrist actigraphy and digital sleep diaries as methods for sleep assessment among high-risk adolescents in the 28 days following discharge from acute psychiatric care. Sleep parameters included: number of nighttime awakenings (NWAK), sleep efficiency (SE), sleep onset latency (SOL), total sleep time (TST), and wake after sleep onset (WASO). MethodsFifty-three adolescents (12–18 years) were recruited following discharge from acute psychiatric care for suicide risk. Adolescents completed a baseline assessment followed by a 28-day monitoring period with daily sleep diaries and continuous wrist actigraphy. Bland-Altman and multi-level models examined agreement. ResultsAdherence to actigraphy was high, but lower for sleep diaries; a similar pattern of adherence emerged on weekdays vs. weekends. Bland-Altman analyses revealed no clinically meaningful bias for sleep parameters (except NWAK), but the limits of agreement make interpretation ambiguous. Our base model indicated strong agreement between actigraphy and sleep diaries for TST (r = 0.850), moderate for SOL (r = 0.325) and SE (r = 0.322), and weak for WASO (r = −0.049) and NWAK (r = 0.114). A similar pattern emerged with the insomnia severity models with baseline insomnia influencing agreement on all parameters. There were significant weekday-weekend differences for WASO and NWAK, but not for SOL, SE, and TST. ConclusionResults suggest that it may be beneficial to find a modeling approach to account for the concordant and discordant information and relevant time-level variables.

Variable Eating Patterns: A Potential Novel Risk Factor for Systemic Inflammation in Women.

The timing and regularity of eating patterns could play a role in systemic inflammation, as circadian clocks responsible for daily rhythms of inflammatory signaling are entrained by food intake. To evaluate associations of intra-weekly and weekday-weekend differences in eating timing patterns with high-sensitivity C-reactive protein (hsCRP). A community-based sample of 103 U.S. women from the American Heart Association Go Red for Women Strategically Focused Research Network completed a meal-timing questionnaire and provided a blood sample for measurement of hsCRP. Differences in weekday versus weekend eating start time, eating end time, and nightly fasting duration were calculated as eating jetlag metrics. Intra-weekly variability in eating timing patterns was defined by the standard deviation (SD) of these variables. Multivariable linear regression models were used to evaluate cross-sectional associations of eating timing variability metrics with hsCRP. Each additional 30-min difference in weekday-weekend eating end time was related to 13% higher hsCRP (p = .023). Similarly, every 30-min increase in eating end time SD, reflecting greater variability in timing of last eating occasion, was associated with 29% higher hsCRP. Per 1-hr weekday-weekend difference in nightly fasting duration, there was a 45% elevation in hsCRP (p = .003). Every 30-min increase in nightly fasting duration SD, representing greater variability in span of the daily fasting/eating periods, was associated with 46% higher hsCRP. Variable eating timing patterns were associated with higher hsCRP. Intervention studies are needed to determine whether stabilizing the timing of eating occasions may represent a novel strategy to reduce chronic inflammation.

Weekend-Weekday Differences in Adherence to the Mediterranean Diet among Spanish University Students.

Daily routines may influence eating patterns; however, differences in intake on weekdays and at weekends have rarely been explored. Furthermore, these differences have not been analyzed among university students (a particularly interesting group among the younger generations). The aim of the study was to evaluate weekend–weekday variation in the Mediterranean diet among Spanish university students, while investigating the potential influence of age, gender, studies, body mass index, smoking status and physical activity status. A repeated-measurement 28-day cross-sectional observational study with self-reported dietary intake collected using the e12HR app was conducted. There were 361 participants: average age 20.6 years; 72.9% women; 58.2% students of Pharmacy; average BMI 21.9 kg/m2; 91.4% nonsmokers; 77.6% performed ≥150 min/week of physical activity. Outcome measurements were adherence to the Mediterranean diet (AMD) index and percentage of participants meeting recommendations for each food group on weekdays and at weekends. In all subgroups, Spanish university students’ global diet was associated with low AMD, with poorer diet quality (>12% reductions in mean scores of AMD index and >26% reductions in adequate adherence scores (≥9)) at weekends. In conclusion, weekend health behaviors of Spanish university students displayed less favorable eating behavior, making the weekend an important target for public health interventions aiming to improve dietary intake.

Preliminary Evidence That Circadian Alignment Predicts Neural Response to Monetary Reward in Late Adolescent Drinkers.

BackgroundRobust evidence links sleep and circadian rhythm disturbances to alcohol use and alcohol-related problems, with a growing literature implicating reward-related mechanisms. However, the extant literature has been limited by cross-sectional designs, self-report or behavioral proxies for circadian timing, and samples without substantive alcohol use. Here, we employed objective measures of sleep and circadian rhythms, and an intensive prospective design, to assess whether circadian alignment predicts the neural response to reward in a sample of late adolescents reporting regular alcohol use.MethodsParticipants included 31 late adolescents (18–22 y/o; 19 female participants) reporting weekly alcohol use. Participants completed a 14-day protocol including pre- and post-weekend (Thursday and Sunday) circadian phase assessments via the dim light melatonin onset (DLMO), in counterbalanced order. Sleep-wake timing was assessed via actigraphy. Circadian alignment was operationalized as the DLMO-midsleep interval; secondary analyses considered social jet lag based on weekday-weekend differences in midsleep or DLMO. Neural response to reward (anticipation and outcome) was assessed via a monetary reward fMRI task (Friday and Monday scans). Alcohol use was assessed at baseline and via ecological momentary assessment. Mean BOLD signal was extracted from two regions-of-interest (striatum and medial prefrontal cortex, mPFC) for analyses in regression models, accounting for age, sex, racial identity, and scan order.ResultsIn primary analyses, shorter DLMO-midsleep intervals (i.e., greater misalignment) on Thursday predicted lower striatal and mPFC responses to anticipated reward, but not reward outcome, on Friday. Lower neural (striatum and mPFC) responses to anticipated reward on Friday correlated with more binge-drinking episodes at baseline, but were not associated with alcohol use in the post-scan weekend. In secondary analyses, greater social jet lag (particularly larger weekend delays in midsleep or DLMO) was associated with lower neural responses to reward anticipation on Monday.ConclusionFindings provide preliminary evidence of proximal associations between objectively determined circadian alignment and the neural response to anticipated monetary reward, which is linked in turn to patterns of problematic drinking. Replication in a larger sample and experimental designs will be important next steps to determining the extent to which circadian misalignment influences risk for alcohol involvement via alterations in reward function.

Sleeping through COVID-19: a longitudinal comparison of 2019 and 2020 infant auto-videosomnography metrics.

With the outbreak of the COVID-19 pandemic, pediatric experts called attention to the potential adverse effects of living restrictions (e.g., lockdown) on child well-being, but at the same time- acknowledged their possible benefits. To date, only few data-driven reports have been published on child sleep during COVID-19, and all have been based on parent- or self-reports. This study used auto-videosomnography to capture the effects of COVID-19 stay-at-home orders imposed in the USA on objectively measured infant sleep. Auto-videosomnography metrics of infants assessed nightly between January and May 2020 were compared with metrics of an equivalent infant cohort, assessed in the corresponding 2019 period. A total of 610 infants (50.7% girls) aged 6-18 months (M = 11.8, SD = 3.6) were included, with 71,472 analyzed nights. Multilevel models were applied to assess differences between 2019 and 2020 infant sleep pre- and during-lockdown. Whereas infant cohorts were equivalent in demographic and January-March/April sleep characteristics, during the 2020 lockdown infants had longer nighttime sleep durations (Mdifference = 11.0 min, p = .01), later morning rise times (Mdifference = 9.5 min, p = .008), and later out-of-crib times (Mdifference = 12.3 min, p < .0001), compared to the equivalent 2019 period. In addition, weekday-weekend differences in sleep onset and midpoint times were diminished during 2020 home-confinement compared to the equivalent 2019 period (2019: Mdifference = 5.5 min, p < .0001; Mdifference = 4.5 min, p < .0001; 2020: Mdifference = 2.3 min, p = .01; Mdifference = 3.1 min, p < .0001, respectively). Notwithstanding the negative implications of COVID-19 living restrictions in other domains, our findings indicate that there might be a silver lining-in promoting longer and more consistent infant sleep. These benefits should be considered in determining policy for the current and future pandemics.

Impact of COVID-19 Controls on the Use of Illicit Drugs and Alcohol in Australia.

Methamphetamine, MDMA, cocaine, cannabis, and alcohol in samples from 20 wastewater treatment plants servicing the eight state or territory capitals of Australia were analyzed, with equivalent coverage of >45% of the national population. Trends in drug consumption were calculated and assessed from samples collected from 2016 to 2020, with a focus on pre-COVID-19 (August 2016 to December 2019), versus February to June 2020, when Australia observed a nationwide lockdown. Results showed delayed but significant decreases in methamphetamine, >50% in Western Australia. In contrast, significant increases in cannabis in most jurisdictions were observed. This suggests changes in consumption may be somewhat linked to reduced supply of imported substances, with increased use of locally produced drugs. Initial decreases in cocaine and MDMA consumption were evident in many parts of the country, but pre-COVID trends were re-established after April 2020. Interestingly, weekend–weekday differences were narrowed for cocaine, MDMA, and alcohol during lockdown, which might be expected due to bars being closed and social gathering not allowed. With this study providing insight into the first four months of COVID-19 restrictions in Australia, it remains to be seen what the longer-term effect of the pandemic will be.

Characteristics and Source Apportionment of Black Carbon (BC) in a Suburban Area of Klang Valley, Malaysia

Black carbon (BC) is of concern due to its contribution to poor air quality and its adverse effects human health. We carried out the first real-time monitoring of BC in Malaysia using an AE33 Aethalometer. Measurements were conducted between 1 January and 31 May 2020 in a university area in a suburban location of the Klang Valley. The measurement period coincided with the implementation of a movement control order (MCO) in response to COVID-19. The mean concentration of BC before the MCO was 2.34 µg/m3 which decreased by 38% to 1.45 µg/m3 during the MCO. The BC is dominated by fossil-fuel sources (mean proportion BCff = 79%). During the MCO, the BCff concentration decreased by more than the BCbb concentration derived from biomass burning. BC and BCff show very strong diurnal cycles, which also show some weekday–weekend differences, with maxima during the night and just before noon, and minima in the afternoon. These patterns indicate strong influences on concentrations from both traffic emissions and boundary layer depth. BC was strongly correlated with NO2 (R = 0.71), another marker of traffic emission, but less strongly with PM2.5 (R = 0.52). The BC absorption Ångström exponent (AAE) ranged between 1.1 and 1.6. We observed pronounced diurnal cycles of lower AAE in daytime, corresponding to BCff contributions from traffic. Average AAE also showed a pronounced increase during the MCO. Our data provides a new reference for BC in suburban Malaysia for the public and policy-makers, and a baseline for future measurements.

214 Longitudinal Changes in Sleep Duration, Timing, Variability, and Stages during the COVID-19 Pandemic: Large-Scale Fitbit Data

IntroductionThe COVID-19 pandemic has resulted in societal-level changes to sleep and other behavioral patterns. Objective, longitudinal data would allow for a greater understanding of sleep-related changes at the population level.MethodsN= 163,524 deidentified active Fitbit users from 6 major US cities contributed data, representing areas particularly hard-hit by the pandemic (Chicago, Houston, Los Angeles, New York, San Francisco, and Miami). Sleep variables extracted include nightly and weekly mean sleep duration and bedtime, variability (standard deviation) of sleep duration and bedtime, and estimated arousals and sleep stages. Deviation from similar timeframes in 2019 were examined. All analyses were performed in Python.ResultsThese data detail how sleep duration and timing changed longitudinally, stratified by age group and gender, relative to previous years’ data. Overall, 2020 represented a significant departure for all age groups and both men and women (P<0.00001). Mean sleep duration increased in nearly all groups (P<0.00001) by 5-11 minutes, compared to a mean decrease of 5-8 minutes seen over the same period in 2019. Categorically, sleep duration increased for some and decreased for others, but more extended than restricted. Sleep phase shifted later for nearly all groups (p<0.00001). Categorically, bedtime was delayed for some and advanced for others, though more delayed than advanced. Duration and bedtime variability decreased, owing largely to decreased weekday-weekend differences. WASO increased, REM% increased, and Deep% decreased. Additional analyses show stratified, longitudinal changes to sleep duration and timing mean and variability distributions by month, as well as effect sizes and correlations to other outcomes.ConclusionThe pandemic was associated with increased sleep duration on average, in contrast to 2019 when sleep decreased. The increase was most profound among younger adults, especially women. The youngest adults also experienced the greatest bedtime delay, in line with extensive school-start-times and chronotype data. When given the opportunity, the difference between weekdays and weekends became smaller, with occupational implications. Sleep staging data showed that slightly extending sleep minimally impacted deep sleep but resulted in a proportional increase in REM. Wakefulness during the night also increased, suggesting increased arousal despite greater sleep duration.Support (if any)This research was supported by Fitbit, Inc.

Changes in sleep duration, timing, and variability during the COVID-19 pandemic: Large-scale Fitbit data from 6 major US cities

The COVID-19 pandemic has resulted in societal-level changes to sleep and other behavioral patterns. Objective data would allow for a greater understanding of sleep-related changes at the population level. About 163,524 active Fitbit users from 6 major US cities contributed data, representing areas particularly hard-hit by the pandemic (Chicago, Houston, Los Angeles, New York, San Francisco, and Miami). Sleep variables extracted include nightly and weekly mean sleep duration and bedtime, and variability (standard deviation) of sleep duration and bedtime. Deviation from similar timeframes in 2018 and 2019 were examined, as were changes in these sleep metrics during the pandemic, relationships to changes in resting heart rate, and changes during re-opening in May and June. Overall, compared to 2019, mean sleep duration in 2020 was higher among nearly all groups, mean sleep phase shifted later for nearly all groups, and mean sleep duration and bedtime variability decreased for nearly all groups (owing to decreased weekday-weekend differences). Over the course of January to April 2020, mean sleep duration increased, mean bedtime shifted later, and mean sleep duration variability decreased. Changes in observed resting heart rate correlated positively with changes in sleep and negatively with activity levels. In later months (May and June), many of these changes started to drift back to historical norms.

Accelerometer-Measured Physical Activity and Sedentary Behavior Levels and Patterns in Female Sixth Graders: The CReActivity Project.

Regular physical activity (PA) and low levels of sedentary behavior (SB) have positive health effects on young people. Adolescent girls of low socioeconomic background represent a high-risk group with regard to physical inactivity and SB. In this study, accelerometer-measured levels of PA and SB of female sixth graders attending lower secondary schools in Germany are presented, patterns of PA and SB throughout the day are described and differences between weekdays and weekend days are analyzed. Data of 425 students of the CReActivity project were analyzed. Sampling and processing of accelerometer data followed recent recommendations, which had not been applied to data of a German-speaking sample before. The WHO recommendation of daily 60 min moderate-to-vigorous PA was fulfilled by 90.4% of the girls on weekdays and by 57.4% on weekend days. The significant weekday–weekend differences were mainly associated with active commuting to and from school. Students engaged in SB for more than 8 h on weekdays and for over 7 h on weekend days. The results suggest a strong need for interventions increasing PA and reducing SB, especially during school hours and on weekends. Furthermore, a comparison with methods and results of previous studies highlights the need to follow recent criteria in accelerometer data sampling and processing to ensure an accurate and valid differentiation between PA-related risk groups and non-risk groups.

Ozone weekend effect in cities: Deep insights for urban air pollution control

Studying weekend-weekday variation in ground-level ozone (O3) allows one to better understand O3 formation conditions, with a potential for developing effective strategies for O3 control. Reducing inappropriately the O3 precursors emissions can either produce no reduction or increase surface O3 concentrations. This paper analyzes the weekend-weekday differences of O3 at 300 rural and 808 urban background stations worldwide from 2005 to 2014, in order to investigate the O3 weekend effect over time and assess the effectiveness of the precursors emissions control policies for reducing O3 levels. Data were analyzed with the non-parametric Mann-Kendall test and Theil-Sen estimator. Rural sites typically did not experience a weekend-weekday effect. In all urban stations, the mean O3 concentration on the weekend was 12% higher than on weekdays. Between 2005 and 2014, the annual mean of daily O3 concentrations increased at 74% of urban sites worldwide (+ 0.41 ppb year−1) and decreased in the United Kingdom (- 0.18 ppb year−1). Over this time period, emissions of O3 precursors declined significantly. However, a greater decline in nitrogen oxides (NOx) emissions caused an increase in Volatile Organic Compounds (VOCs) to NOx ratios leading to O3 formation. In France, South Korea and the United Kingdom, most urban stations showed a significant upward trend (+ 1.15% per year) for O3 weekend effect. Conversely, in Canada, Germany, Japan, Italy and the United States, the O3 weekend effect showed a significant downward trend (- 0.26% per year). Further or inappropriate control of anthropogenic emissions in Canada, Southern Europe, Japan, South Korea and the United States might result in increased daily O3 levels in urban areas.

Frequency and Correlates of Sleep Debt in St. Petersburg

During weekdays, many of us fail meeting their physiologic sleep need. During weekends, however, when given additional sleep opportunity, homeostatic sleep pressure will typically lead to longer bedtimes, manifesting the cumulative sleep debt. This study aims at examining the prevalence and determinants of sleep debt, as indicated by the presence of ≥ 2 h weekend bedtime prolongation, in a general population. We studied 257 healthy subjects living in St. Petersburg, Russia. All participants indicated their habitual bedtimes during weekdays and weekends, and completed the Epworth Sleepiness Scale (ESS), Fatigue Severity Scale, Fatigue Impact Scale, Pittsburgh Sleep Quality Index, and Hospital Anxiety and Depression Scale. One-hundred-three participants (40%) exhibited a relevant sleep debt (≥ 2 h weekend–weekday difference in habitual bedtime). Compared to participants without sleep debt, the frequency of excessive daytime sleepiness (ESS score ≥ 11)—but not of fatigue, impaired sleep quality and mood disturbances—was higher in participants with sleep debt (21% vs. 10%, p = 0.01). Multiple regression analysis revealed younger age, higher ESS and lower body mass index as independent associates of sleep debt. Sleep debt appeared to be very common among healthy subjects, and independently associated with younger age, higher ESS scores and lower BMI. However, the presence of sleep debt did not have an impact on fatigue or mood, as measured by validated questionnaires.