Obesity alters the circadian profiles of energy metabolism and glucose regulation in humans.

OBJECTIVE: Given the complex interaction among the circadian system, energy metabolism, and obesity, the authors tested whether having obesity impacts the circadian variation in energy and glucose metabolism in humans. METHODS: Participants with BMI either in the healthy weight or obesity ranges were studied in a 5-day, in-laboratory protocol that equally distributed behaviors (i.e., sleep, eating, exercise) across 24 h. Energy metabolism was measured at rest and during a standardized exercise bout and blood was sampled before and after each identical study meal to assess glucose and insulin levels. RESULTS: In those with a healthy weight, the circadian nadir of energy expenditure, during both rest and exercise, occurred when participants would normally be asleep. However, in those with obesity, this nadir appears to occur during the habitual wake period. Differences in glucose regulation also depended on the circadian phase, such that individuals with obesity appeared to have relatively greater glucose intolerance during the circadian day and produced less insulin during the circadian night. CONCLUSIONS: Obesity is associated with altered circadian energy and glucose metabolism. Understanding and addressing these associations could lead to strategies that improve body weight and metabolic health in people with obesity.

UCLMuevete: Increasing the amount of physical activity, work-ability, and cardiorespiratory fitness capacity in university workers through active breaks.

BACKGROUND: Active break programs at the workplace are a promising initiative for increasing workers' physical activity (PA) levels, health, work-ability (WA), and social relationship. OBJECTIVE: To determine the impact of an Active Breaks workplace program based on Bandura's Social Cognitive Theory (SCT) aligned with Behavior Change Techniques (BCT) on PA levels, cardiorespiratory fitness (CRF), WA, and social relationships among university workers. METHODS: #UCLMuévete is a quasi-experimental, 12-week intervention designed according to the TREND and TIDieR-PHP checklists. Sixty-nine university workers were recruited and placed into 17 teams of 3 to 5 people. Participants were instructed to take a 20-min active break every working day (walking, cycling, and functional training). The following variables were measured before and after the 12-week intervention: (1) Amount of PA with accelerometers, (2) CRF through the 6 Min-Walking Test (m), (3) Body composition (fat mass (gr), muscle mass (gr), and bone mineral content (g/cm3) through densitometry), (4) Stress with the BodyGuard2 device, (5) WA through Work Ability Index (WAI), and (6) Social relationships through an ad-hoc questionnaire. Part-time workers, pregnant women, and workers with physical disability were excluded. RESULTS: Significant improvements were observed in the amount of daily moderate-to-vigorous PA (Difference (Dif)., women +8.05 and men +12.31 minutes; p < 0.05; ES = 0.224; 0.379), CRF (Dif., women +52.98 and men +25.53 meters; p < 0.05; ES = 0.578; 0.209), and (Dif., women +2.16 and men +2.39; p < 0.05; ES = 0.150; 0.177). No significant changes were observed in body composition and stress. CONCLUSION: 20 min/day of aerobic and strength active breaks, based on SCT aligned to BCTs, improves university workers' amount of PA, CRF, WAI, and social relationships.

Chronological distribution of readings in ambulatory blood pressure monitoring exams affects the nighttime average and the magnitude of blood pressure dipping.

STUDY OBJECTIVES: Averaged nighttime blood pressure (BP) is superior to daytime BP for cardiovascular risk stratification, and the relative change between daytime/nighttime BP (dipping%) significantly predicts cardiovascular risk. Newer reports suggest that 4 measurements at night may be enough for cardiovascular risk stratification. Since BP oscillates across the night, the temporal distribution of measurements across the night may impact nighttime BP and dipping%. Therefore, we compared average nighttime BP and dipping% when using measurements in the first half (1st-half), second (2nd-half), and a combination of both (combined). METHODS: Forty-three (17 females and twenty-six males) midlife adults aged 50±10 years old wore an ambulatory BP monitor for 24 hours at home, programmed to measure BP every 20 minutes when scheduled for daytime and every 30 minutes during a self-selected 8-hour nighttime for time-in-bed. We compared the nighttime BP averages and dipping% when using either the first four measurements from the 1st-half or 2nd-half of the nighttime and combined. RESULTS: Nighttime Systolic BP was significantly different across 1st-half, 2nd-half, and combined (111±9 vs.107±11 vs. 109±9 mmHg, p<0.01), respectively, with significant pairwise differences across all categories (p<0.01 for each). Systolic BP dipping% was significantly different across 1st-half, 2nd-half, and combined (9.9±5.5 vs.13.5±6.4 vs. 11.7±5.0 %, p<0.01), respectively, with significant pairwise differences across all categories (p<0.01 for each. Diastolic BP and diastolic dipping% were similar across the three different bins. CONCLUSION: In midlife adults, systolic nighttime BP and dipping% may depend upon when BP measurements are taken during the night.

Effectiveness of worksite wellness programs based on physical activity to improve workers' health and productivity: a systematic review.

BACKGROUND: Although the scientific literature has previously described the impact of worksite programs based on physical activity (WPPAs) on employees' productivity and health in different contexts, the effect of these programs has not been analyzed based on the characteristics or modalities of physical activity (PA) performed (e.g., aerobic exercise, strength training, flexibility). In addition, studies on WPPAs usually report health and productivity outcomes separately, not integrated into a single study. Knowing the health and economic-related impacts of a WPPAs could provide useful information for stakeholders and policy development. OBJECTIVE: The purpose of this review was as follows: (1) to analyze the effect of different modalities of WPPAs on employees' productivity and health and (2) to investigate the economic impact of WPPAs. METHODS: This systematic review is registered in PROSPERO (CRD42021230626) and complies with PRISMA guidelines. Only randomized controlled trials from 1997 to March 2021 were included. Two reviewers independently screened abstracts and full texts for study eligibility, extracted the data, and performed a quality assessment using the Cochrane Collaboration Risk-of-Bias Tool for randomized trials. Population, instruments, comparison, and outcome (PICO) elements were used to define eligibility criteria. Eight-hundred sixty relevant studies were found through electronic searches in PubMed, Web of Science, Medline, Scopus, and SPORTDiscus databases. Once the eligibility criteria were applied, a total of 16 papers were included. RESULTS: Workability was the productivity variable most positively impacted by WPPAs. Cardiorespiratory fitness, muscle strength, and musculoskeletal symptoms health variables improved in all the studies included. It was not possible to fully examine the effectiveness of each exercise modality because of the heterogeneity in methodology, duration, and working population. Finally, cost-effectiveness could not be analyzed because this information was not reported in most studies. CONCLUSION: All types of WPPAs analyzed improved workers' productivity and health. However, the heterogeneity of WPPAs does not allow to identify which modality is more effective.

Resting coronary flow drives the daily pattern in coronary flow reserve in patients with chest pain without obstructive epicardial stenosis.

Objectives: Ischemia with no obstructive coronary artery disease (INOCA) is a risk factor for major adverse cardiovascular events and is characterized by abnormal coronary microvascular tone. In patients with INOCA, adverse cardiovascular events most commonly occur in the morning compared to other times of the day and night. Materials and methods: We tested whether coronary microvascular function varies diurnally with attenuation in the morning in patients with symptomatic coronary artery disease without significant (>50%) epicardial stenosis. We evaluated data from 17 patients studied in the AM (700-1159 h) and 11 patients in the PM (1200-1800 h). Coronary microvascular function was measured using perfusion contrast imaging at rest and after infusion of intravenous regadenoson. We calculated microvascular flow reserve as the ratio of hyperemic to resting flow. Along with independent sample t-tests, we performed bootstrapping procedures to test mean differences between AM and PM groups, using the bias-corrected and accelerated method with 5,000 bootstrapped samples. Results and conclusion: The AM and PM groups were matched for demographic and existing risk factors. Coronary microvascular flow reserve was ∼33% higher in the AM compared to the PM (P = 0.025, BCa 95% CI [0.25, 1.64]; Hedge's g = 0.89, 95% CI [0.11, 1.66]) as a result of significantly lower resting flow (∼50%) in the AM compared to the PM (P = 0.03, M Diff = -56.65, BCa 95% CI [-118.59, -2.12]; Hedge's g = -0.86, 95% CI [-1.60, -0.06]). Our observations are of clinical value and can influence diagnosis and treatment in the clinic based on the time of day of measurements.

The circadian system modulates the cortisol awakening response in humans.

Background: In humans, circulating cortisol usually peaks 30-60 min after awakening from nocturnal sleep, this is commonly referred to as the cortisol awakening response (CAR). We examined the extent to which the CAR is influenced by the circadian system, independent of behaviors including sleep. Materials and methods: We examined the CAR in 34 adults (20 female) using two complementary multiday in-laboratory circadian protocols performed in dim light, throughout which behavioral factors were uniformly distributed across the 24-hour circadian cycle. Protocol 1 consisted of 10 identical consecutive 5-hour 20-minute sleep/wake cycles, and protocol 2 consisted of 5 identical consecutive 18-hour sleep/wake cycles. Salivary melatonin was used as the circadian phase marker (0° = dim light melatonin onset). During each sleep/wake cycle, salivary cortisol was measured upon scheduled awakening and 50-minutes later, with the change in cortisol defined as the CAR. Cosinor analyses were used to detect any significant circadian rhythmicity in the CAR. In secondary analyses, we adjusted the models for time awake before lights on, total sleep time, percent of rapid eye movement (REM) sleep, and percent of non-rapid eye movement (NREM) sleep. Results: Both protocols revealed a similar circadian rhythm in the CAR, with peaks occurring at a circadian phase corresponding to 3:40-3:45 a.m., with no detectable CAR during the circadian phases corresponding to the afternoon. In addition to the sinusoidal component of the circadian rhythm, total sleep time was also associated with the CAR for protocol 1. The percent of sleep spent in REM or NREM sleep were not associated with the CAR in either protocol. Conclusion: Our results show that the CAR exhibits a robust circadian rhythm that persists even after adjusting for prior sleep. Presuming that the CAR optimizes physiological responses to the anticipated stressors related to awakening, these findings may have implications for shift workers who wake up at unusual circadian phases. A blunted CAR in shift workers upon awakening in the evening may result in diminished responses to stressors.

Chronobiology of Exercise: Evaluating the Best Time to Exercise for Greater Cardiovascular and Metabolic Benefits.

Physiological function fluctuates across 24 h due to ongoing daily patterns of behaviors and environmental changes, including the sleep/wake, rest/activity, light/dark, and daily temperature cycles. The internal circadian system prepares the body for these anticipated behavioral and environmental changes, helping to orchestrate optimal cardiovascular and metabolic responses to these daily changes. In addition, circadian disruption, caused principally by exposure to artificial light at night (e.g., as occurs with night-shift work), increases the risk for both cardiovascular and metabolic morbidity and mortality. Regular exercise is a countermeasure against cardiovascular and metabolic risk, and recent findings suggest that the cardiovascular benefits on blood pressure and autonomic control are greater with evening exercise compared to morning exercise. Moreover, exercise can also reset the timing of the circadian system, which raises the possibility that appropriate timing of exercise could be used to counteract circadian disruption. This article introduces the overall functional relevance of the human circadian system and presents the evidence surrounding the concepts that the time of day that exercise is performed can modulate the cardiovascular and metabolic benefits. Further work is needed to establish exercise as a tool to appropriately reset the circadian system following circadian misalignment to preserve cardiovascular and metabolic health. © 2022 American Physiological Society. Compr Physiol 12:3621-3639, 2022.

Sleep Efficiency is Inversely Associated with Brachial Artery Diameter and Morning Blood Pressure in Midlife Adults, with a Potential Sex-Effect.

PURPOSE: Sleep efficiency is inversely associated with cardiovascular risk. Brachial artery diameter and flow-mediated dilation (FMD) are noninvasive cardiovascular disease markers. We assessed the associations between sleep efficiency and these vascular markers in midlife adults, including people with sleep apnea. PATIENTS AND METHODS: Thirty (18 males) participants completed an in-laboratory 8-hour sleep opportunity beginning at their habitual bedtimes. Polysomnography was used to assess sleep patterns and sleep efficiency (time asleep/time in bed). We measured systolic and diastolic blood pressure, heart rate, and baseline diameter, and FMD immediately upon awakening in the morning. Mixed model analyses, adjusting for apnea-hypopnea and body mass indices, were used to assess the relationship between overnight sleep efficiency and cardiovascular markers. We also explored sex differences. RESULTS: Sleep efficiency was negatively associated with baseline brachial artery diameter (p = 0.005), systolic BP (p = 0.01), and diastolic BP (p = 0.02), but not flow-mediated dilation or heart rate (p > 0.05). These relationships were confirmed with correlations between sleep efficiency and baseline diameter (r = -0.52, p = 0.004), systolic BP (r = -0.43, p = 0.017), and diastolic BP (r = -0.43, p = 0.019). There was a sex-specific interaction trend for sleep efficiency and arterial diameter (p = 0.07) and a significant sex-specific interaction (p < 0.05) for BP, such that the relationships between sleep efficiency and cardiovascular markers were significant in women but not in men. CONCLUSION: In midlife adults, poor sleep efficiency is associated with increased brachial artery diameter and blood pressure, effects that were primarily driven by significant associations in women. These associations could underlie the observed increase in cardiovascular risk in adults with poor sleep and cardiovascular disease.

Shorter Sleep Predicts Longer Subsequent Day Sedentary Duration in Healthy Midlife Adults, but Not in Those with Sleep Apnea.

PURPOSE: Sedentary behavior and suboptimal sleep increase risks for chronic diseases. We hypothesized that sedentary behavior and sleep affect each other and that an underlying sleep disorder would alter these relationships. To test these hypotheses, we studied the bidirectional relationships between sedentary behavior and sleep (duration and efficiency) in healthy controls (HC) and people with untreated obstructive sleep apnea (OSA). PATIENTS AND METHODS: Fifty-two volunteers (18 HC, 19 mild OSA [apnea/hypopnea index [AHI] range 5-14.9/hour], 15 moderate OSA [AHI range 15-29.9/hour]) were studied with actigraphy and sleep diaries across ~9 consecutive nights of self-selected consistent ~8-hour sleep episodes at home (range 4-21/nights per person). We analyzed whether total time asleep and sleep efficiency affected the subsequent daytime sedentary duration while controlling for body mass index and whether the severity of OSA altered this relationship. We also tested the reverse relationship, namely whether daytime sedentary duration affected the subsequent night's sleep and if any such relationship differed with OSA severity. RESULTS: Overnight sleep duration and efficiency negatively predicted the subsequent day's sedentary duration in HC (p<0.02), but not in people with mild or moderate OSA (p>0.05). There was no significant reverse relationship between daytime sedentary duration and the subsequent night's sleep duration or efficiency (p≥0.2). CONCLUSION: In healthy adults, short nighttime sleep predicts a longer duration of sedentary behavior on a subsequent day, but we did not observe this relationship in people with OSA. The mechanisms underlying this association in healthy individuals and its disruption in the presence of OSA need to be studied.

Sedentary Work and Physiological Markers of Health.

The purpose of this study is to examine associations between objectively measured workplace sedentary behavior and physiological markers of health. We hypothesize that increased sedentary time and more frequent bouts of uninterrupted sitting are associated with increased hemoglobin A1c, increased blood pressure, and impaired endothelial function. Call center employees (N = 241) were enrolled from four worksites in the United States. Participants completed a survey and a physical health assessment. Sedentary behavior and sitting/standing time at work were quantified using an accelerometer. Hemoglobin A1c was measured using a finger-prick and portable analyzer. Blood pressure was measured with an automated cuff, and vascular endothelial function was assessed in a subsample of participants (n = 56) using EndoPAT. We analyzed data with two series of ordinary least squares regressions, first to examine relationships between bouts of uninterrupted sitting and physiological outcomes, and second to examine relationships between physical activity and sitting/standing time at work and physiological outcomes. The sample was primarily female, and on average was obese, prehypertensive, and prediabetic. There were no significant relationships between bouts of uninterrupted sitting or physical activity/sitting/standing time at work and physiological outcomes. In a sample that is predominantly sedentary, at risk for cardiovascular disease, and prediabetic, there are no significant associations between workplace sedentary behavior and physiological markers. The lack of associations could be related to either physiological adaptations or ceiling effects in this sample.

Circadian control of human cardiovascular function.

Endogenous circadian rhythms prepare the cardiovascular (CV) system for optimal function to match the daily anticipated behavioral and environmental cycles, including variable activities when awake during the day and recuperation when sleeping at night. The overall day-night patterns in most CV variables result from the summation of predictable circadian effects with variable behavioral and environmental effects on the CV system. The circadian system has also been implicated in the morning peak in the incidence of adverse CV events, including myocardial infarction, stroke, and sudden cardiac death. We discuss the resting and stress-reactive circadian control of CV physiology in humans and suggest future research opportunities, including improving CV therapy by optimally timing therapy relative to a person's internal body clock time.

The active workplace study: Protocol for a randomized controlled trial with sedentary workers.

OBJECTIVES: Sedentary behavior is pervasive in the workplace and is harmful to health. Research on the effectiveness of comprehensive workplace interventions to reduce sedentary behavior and improve worker health and safety is crucial as sedentary jobs become more common. METHODS: We developed a Total Worker Health intervention targeting sedentary behavior in call centers, and are evaluating intervention effectiveness in a randomized controlled trial. Four worksites will be randomly assigned to an intervention or control condition. The intervention condition includes the provision of active workstations along with programs and procedures at environmental, organizational, and individual levels. Control worksites will receive active workstations with no additional support, following common organizational practices. RESULTS: Outcomes include objectively measured physical activity, biological markers of health, and self-report survey data at baseline, after the 6-month intervention or control period, and at a 12-month follow-up. CONCLUSIONS: The aims of the study are to determine whether a Total Worker Health intervention has stronger impacts on workplace sedentary behavior, uninterrupted bouts of sitting, and worker health and safety compared to a usual practice control condition. The study will inform future workplace sedentary behavior intervention and dissemination research, along with organizational best practices for reducing sedentary behavior in the workplace.

Biological pathways underlying the association between habitual long-sleep and elevated cardiovascular risk in adults.

Cardiovascular disease is the leading cause of death in the world. In addition to non-modifiable factors such as age and sex, cardiovascular risk is also driven by behavioral, and therefore somewhat modifiable, factors such as physical activity, diet, and sleep. It is well established that sleep duration has a U-shaped association with mortality and cardiovascular disease, with recent evidence suggesting that this association is observed even while controlling for the effects of comorbid conditions. Whereas several biological mechanisms mediating the association between chronic short sleep duration and cardiovascular risk have been established, the biological mechanisms underlying the relationship between habitual long sleep (≥9 h) duration and cardiovascular risk, in the absence of other chronic diseases, are not well understood. This review will focus on summarizing the literature investigating the mechanisms underlying the association between habitual long sleep duration and cardiovascular risk. We will also propose the mechanistic pathways, distinct from the ones for short sleep, by which habitual long sleep can increase cardiovascular disease.

Circadian rhythm in negative affect: Implications for mood disorders.

In humans, there is an endogenous, near 24-h (i.e., circadian) variation in mood with the best mood occurring during the circadian day and the worst mood occurring during the circadian night. Only positive affect, and not negative affect, has been shown to contribute to this circadian rhythm. We discovered a sharp circadian peak in negative affect during the circadian night coincident with a circadian trough in positive affect. These findings may help explain the association of depression with insomnia, the increased risk of suicide with nocturnal wakefulness, and the correlation between circadian misalignment and symptom severity in Major Depressive Disorder.

Effects of obstructive sleep apnea on endogenous circadian rhythms assessed during relaxed wakefulness; an exploratory analysis.

Obstructive sleep apnea (OSA) is associated with hypertension, cardiovascular disease, and a change in the 24 h pattern of adverse cardiovascular events and mortality. Adverse cardiovascular events occur more frequently in the middle of the night in people with OSA, earlier than the morning prevalence of these events in the general population. It is unknown if these changes are associated with a change in the underlying circadian rhythms, independent of behaviors such as sleep, physical activity, and meal intake. In this exploratory analysis, we studied the endogenous circadian rhythms of blood pressure, heart rate, melatonin and cortisol in 11 participants (48 ± 4 years; seven with OSA) throughout a 5 day study that was originally designed to examine circadian characteristics of obstructive apnea events. After a baseline night, participants completed 10 recurring 5 h 20 min behavioral cycles divided evenly into standardized sleep and wake periods. Blood pressure and heart rate were recorded in a relaxed semirecumbent posture 15 minutes after each scheduled wake time. Salivary melatonin and cortisol concentrations were measured at 1-1.5 h intervals during wakefulness. Mixed-model cosinor analyses were performed to determine the rhythmicity of all variables with respect to external time and separately to circadian phases (aligned to the dim light melatonin onset, DLMO). The circadian rhythm of blood pressure peaked much later in OSA compared to control participants (group × circadian phase, p < .05); there was also a trend toward a slightly delayed cortisol rhythm in the OSA group. Rhythms of heart rate and melatonin did not differ between the groups. In this exploratory analysis, OSA appears to be associated with a phase change (relative to DLMO) in the endogenous circadian rhythm of blood pressure during relaxed wakefulness, independent of common daily behaviors.