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.

Belonging, endurance, and resistance: Black placemaking theory in primary care

Black-Americans continue to experience pervasive health disparities. Factors contributing to increased disease risk include a general mistrust of biomedical institutions among Black Americans. The purpose of this focus group study was to identify, among Black patients who regularly seek care from a primary provider, salient themes regarding barriers to 1) receiving quality primary care; and 2) adhering to medical recommendations. We examined transcripts of eight focus groups held remotely with 29 Black patients (aged 30-60 years) who had established primary care providers. Using grounded theory and an inductive thematic analysis of the transcripts, we identified three themes (belonging, endurance, and resistance) consistent with Black placemaking theory. Our findings suggest that reducing health disparities for Black Americans will require clinical initiatives that emphasize: 1) attention to social influences on health behavior and to features of medical institutions that mark them as White spaces (belonging); 2) recognition of, as well as sensitivity to, community awareness of the systemic and interpersonal barriers to health and safety that many Black adults endure; and 3) reframing avoidant (resistant) behaviors as protective strategies among Black patients. Examining primary care in this way-through the lens of Black placemaking theory-reveals how culturally meaningful approaches to harnessing the specialized knowledge and resilience that clearly exists among many Black communities can improve health care delivery.

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.

Daily cannabis use is associated with sleep duration differentially across ages

OBJECTIVE

To assess the relationship between frequency of cannabis use and sleep duration across age in a large US population (235,667 people).

METHODS

Multinomial logistic regression was used to evaluate the association between the frequency of cannabis use and sleep duration using cross sectional data from the 2016-2018 Behavioral Risk Factor Surveillance System.

RESULTS

When adjusted for sociodemographic factors, health related variables, and stratified by age we found that young adults (18-44 years) who reported daily-use (≥16 uses a month) had an increased risk ratio (RR [95% CI]) for either short or long sleep (1.22 [1.06-1.40] and 1.52 [1.07-2.16]); midlife adults (45-64 years) who reported daily-use had an increased prevalence of long sleep (1.71 [1.03-2.82]); and older adults (≥65 years) who reported daily-use had an increased prevalence of short sleep (1.61 [1.05-2.49]).

CONCLUSIONS

Compared to those who reported no cannabis use, individuals who reported daily cannabis use demonstrated a greater prevalence for either short or long sleep duration.

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.

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.

Inverse correlation between plasma 2-arachidonoylglycerol levels and subjective severity of depression

OBJECTIVE

Endocannabinoids have been implicated in the pathophysiology of Major Depressive Disorder (MDD) and might represent potential targets for therapeutic intervention. Objectives of the study were: (1) to measure plasma levels of endocannabinoids in a group of antidepressant-free depressed outpatients; (2) to explore their relationship with the severity of depressive symptoms as subjectively perceived by the patients; and (3) to investigate the effect of the selective serotonin reuptake inhibitor escitalopram on endocannabinoid levels.

METHODS

We measured plasma levels of the two major endocannabinoids, 2-arachidonoylglycerol (2-AG) and N-arachidonoylethanolamine (anadamide), in 12 drug-free outpatients diagnosed with MDD and in 12 matched healthy controls. In the patient group, endocannabinoids plasma levels were assessed at baseline and after 2 months of treatment with escitalopram.

RESULTS

Baseline plasma levels of the two endocannabinoids did not differ between depressed patients and healthy controls. However, there was a significant inverse correlation between 2-arachidonoylglycerol levels and the severity of subjectively perceived depressive symptoms. Treatment with escitalopram did not change endocannabinoid levels in depressed patients, although it caused the expected improvement of depressive symptoms.

CONCLUSIONS

Our results suggest that 2-arachidonylglycerol, the most abundant endocannabinoid in the central nervous system, might act to mitigate depressive symptoms, and raise the interesting possibility that 2-arachidonylglycerol and anandamide are differentially regulated in patients affected by MDD. Also, our data suggest but do not prove that the endocannabinoid system is not regulated by serotonergic transmission, at least in depressed patients.

Optimization of Primary Care Among Black Americans Using Patient Portals: Qualitative Study

BACKGROUND

Reduced patient portal use has previously been reported among Black Americans when compared with that of the general population. This statistic is concerning because portals have been shown to improve the control of chronic conditions that are more prevalent and severe in Black Americans. At their very simplest, portals allow patients to access their electronic health records and often provide tools for patients to interact with their own health information, treatment team members, and insurance companies. However, research suggests that Black American patients have greater concerns over a lack of support, loss of privacy, and reduced personalization of care compared with other Americans, which results in a disparity of portal use.

OBJECTIVE

This qualitative investigation of primary care experiences of Black Americans from across the United States who participated in remote focus groups in April and May 2020 aims to explore the use and perceived value of patient portals to better understand any barriers to optimized treatment in the primary care setting.

METHODS

We performed an inductive thematic analysis of 8 remote focus group interviews with 29 Black American patients aged 30-60 years to qualitatively assess the experiences of Black American patients with regular access to portals.

RESULTS

Thematic analysis uncovered the following interrelated themes regarding patient portals in primary care: the optimization of care, patient empowerment, patient-provider communication, and patient burden.

CONCLUSIONS

In contrast to what has been described regarding the reluctance of Black Americans to engage with patient portals, our focus groups revealed the general acceptance of patient portals, which were described overwhelmingly as tools with the potential for providing exceptional, personalized care that may even work to mitigate the unfair burden of disease for Black Americans in primary care settings. Thus, opportunities for better health care will clearly arise with increased communication, experience, and adoption of remote health care practices among Black Americans.

Interactions between home, work, and sleep among firefighters

BACKGROUND

Firefighters endure large occupational burdens and generally operate under conditions of chronic sleep deficiency and circadian disruption due to long shifts, plus interrupted sleep due to emergency calls during the night. A typical shift for firefighters is 24-h on/48-h off, and firefighters are expected to use time-off to recover from any sleep debt, while balancing social, family, and home responsibilities. This qualitative study sets out to assess family dynamics and how firefighters prioritize sleep and recovery at home based on relationship or family status, as well as a fire department's current shift schedule.

METHODS

Focus groups were conducted via convenience sampling in Portland, OR, with full-time firefighters, battalion chiefs, and their spouses. Grounded theory, using NVivo 12 Plus, was used to code transcripts to reveal reoccurring concepts and themes.

RESULTS

Major themes centered around the increase of nonemergent calls contributing to compassion fatigue. Spouses can help improve the sleep of firefighters by creating opportunities for recuperative sleep at home. However, spouses also conveyed underlying tones of "resentment" relating to their firefighter being unavailable for emotional and instrumental support. While married firefighters discussed choosing family and home obligations over reducing sleep debt to maintain relationships, single and divorced firefighters spoke of fewer conflicts impeding their ability to prioritize sleep at home.

CONCLUSIONS

These results improve our understanding of how firefighters prioritize sleep at home based on family dynamics and can inform future decision-making for fire departments in addressing concerns related to work-family conflict, sleep loss, and compassion fatigue among their members.

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.

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.

0570 Apnea-Hypopnea Index is Positively Correlated with Mood Disturbance

Introduction

The prevalence of mood disorders such as depression is higher in individuals with obstructive sleep apnea (OSA). Previous studies have found no significant correlation between the apnea-hypopnea index (AHI) and measures of mood and have only included participants who met diagnostic criteria for OSA. The current analysis sought to determine whether mood correlated with AHI in individuals with any AHI values including those that did not meet diagnostic criteria for OSA.

Methods

31 volunteers were studied (BMI=29.2±1.0 kg/m2, mean±SE), free from medication and without psychiatric illness or chronic medical conditions with the exception of untreated OSA, uncomplicated hypertension (BP&lt;160/100), or obesity. Following 1-3 weeks of an 8h habitual at home sleep schedule, participants completed the POMS-Brief questionnaire (POMS-B) to assess mood after undergoing overnight polysomnography to determine AHI. Total mood disturbance (TMD) scores were calculated by adding the scores on the POMS-B for each mood state subscale and subtracting the score for vigor-activity.

Results

The average AHI was 15.3±3.1 (range of 1.1-74.1) events per hour. The average POMS-B TMD score was 21±1.5 (range of 4-46). There was a significant correlation between the POMS-B TMD score and AHI (p=0.037, r2=0.14). This result was also seen in only those individuals with AHI scores &gt;5 (p=0.002, r2=0.4).

Conclusion

In this sample, individuals with higher AHI values displayed higher TMD scores. These results differ from previous data that showed no significant correlation between AHI and TMD. This is the first analysis to demonstrate a correlation between TMD and AHI while including individuals who didn’t meet diagnostic criteria for OSA. However, the relationship between AHI and TMD was also significant in those with AHI&gt;5. More data on these measures with larger sample sizes and a more equal representation of AHI values should be gathered to provide additional evidence for this relationship.

Support: Support

NIH R01-HL125893; CTSA UL1TR000128, R21HL140377

0035 Resting Metabolism and the Metabolic Response to Exercise Follow Circadian Patterns with Day/Night Differences in Substrate Utilization Between Lean and Obese Adults

Introduction

Resting energy expenditure (EE) follows a circadian rhythm in healthy lean participants, with a nadir in the early morning hours. We determined: (1) whether this pattern persists (or how substrate utilization may change), when challenged with exercise, and; (2) whether obesity affects these responses.

Methods

Fourteen participants (aged 48.5±12.8y; 6-female; 5-obese, BMI 31.9±1.4kg/m2 [avg±SD]) underwent a 5-day inpatient forced desynchrony protocol, comprised of ten 5h 20min ‘days’ in dim-lighting and free of time cues. Resting EE was measured immediately prior to a 15-minute cycle ergometer exercise bout at 50% of estimated heart rate maximum. Substrate utilization was determined from the respiratory quotient (RQ). Circadian phase was calculated using the salivary dim-light melatonin onset (&gt;3pg/mL threshold). EE data were analyzed using a mixed-effect model with group (lean vs. obese) and circadian phase as fixed factors; subject was a random factor. RQ was analyzed using t-tests to determine day/night differences in groups at rest and in response to exercise.

Results

Resting and exercising EE both displayed endogenous circadian rhythms (p&lt;0.05) with nadirs in the early morning (~5:30am), without any differences between groups (p&gt;0.22). Resting RQ was similar between the day and night in the lean group (p=0.66), but decreased (suggesting lower carbohydrate utilization) at night within the obese group (-2.5±1.6%, p=0.02). The lean group increased RQ in response to exercise both during the day (+8.9±2.8%) and night (+8.0±2.8%) (both p&lt;0.001), but there was no increase in RQ in the obese group during either day or night exercise (p&gt;0.16).

Conclusion

These data demonstrate that EE during rest and exercise follows a circadian pattern, with limited influence of obesity. Circadian differences in substrate utilization between lean and obese in the resting state and in response to exercise may play a role in expression and maintenance of unwanted weight gain and impaired metabolic health.

Support

R01HL125893, R01HL140577, KL2TR002370, K01HL146992, F32HL131308, Medical Research Foundation of Oregon, Ford Foundation, and CTSA grant (UL1TR000128)

0847 Association Between Cannabis Use Frequency and Sleep Duration Among a Representative Sample of US Adults

Introduction

Cannabis use is on the rise in the US, and while the cannabis plant and related compounds are considered to have low toxicity, the impact on physiology including sleep remains unclear. Further, the bulk of cannabis research has focused on adolescents and young adults despite growing use among the elderly. Thus, this analysis sought to determine the impact of the frequency of cannabis use on sleep duration and determine if this relationship varies by age.

Methods

This cross-sectional study used data from the 2016-2018 Behavioral Risk Factor Surveillance System surveys. Multinomial logistic regression was used to evaluate the association between the frequency of cannabis use, 0-30 times over the prior 30 days; and average sleep duration, short (&lt;7 hours); recommended (7-9 hours); and long (&gt;9 hours) sleep.

Results

The study sample included 235,667 participants (48% male, 43% 18-44 years old and 35% 44-64 years old) of which 14,122 consumed cannabis. The weighted proportion who reported using cannabis 1-4x, 5-15x, or more than 16x/month were 3.1% (95% CI, 3.0%-3.3%), 2.1% (2.0%-2.2%), and 4.4% (4.2%-4.6%) respectively. In an age stratified model adjusted for sociodemographic and clinical characteristics, there were no associations between sleep and cannabis use up to 15x/month. Among those adults who consumed cannabis more than 16x/month: (1) 18-44 year olds were more likely to report either short sleep (risk ratio (RR), 1.21; 95% CI, 1.05-1.39) or long sleep (RR, 1.57; 95% CI, 1.11-2.22) as opposed to the recommended amount of sleep; whereas (2) 44-64 year olds demonstrated an increased risk for long sleep (RR, 1.77; 95% CI, 1.09-2.89); and (3) participants 65 years and older demonstrated an increased risk for short sleep (RR, 1.61; 95% CI, 1.04-2.49).

Conclusion

We demonstrate that modest cannabis use was not associated with sleep, whereas daily cannabis use is associated with age-dependent sleep duration above and below the recommended amount.

Support

KL2TR002370, 2R25HL105444-09.

0223 Interactions Between Home, Work, and Sleep Among Full-Time Firefighters

Introduction

Firefighters endure large occupational burdens (e.g., heat, exposure to toxic fumes, witnessed trauma) and generally operate under conditions of chronic sleep deficiency due to long shifts plus disrupted sleep and circadian disruption due to emergency calls during the night. A typical shift for firefighters is 24-hours on/48-hours off, and firefighters are expected to use time-off to recover from any sleep debt. However, firefighters need to balance that recovery with social/family needs and home maintenance. We conducted focus groups and qualitative analysis of responses to understand how firefighters’ sleep recoverability is affected by occupational burdens and home/family dynamics.

Methods

Focus groups were conducted via convenience sampling in Portland, Oregon, with full-time firefighters, battalion chiefs, and spouses of firefighters to assess current strategies and coping mechanisms used to manage occupational burdens, home/family obligations, and sleep loss based on their 24-hours on/48-hours off shift schedule. Grounded theory, using NVivo 12 plus, was used to code focus group transcripts to reveal reoccurring concepts that were further grouped into themes.

Results

Major themes that emerged among firefighters and spouses (n=48) centered on spousal resentment of firefighters, driven by understanding a firefighters’ heroic occupation and need to recover from accumulated sleep loss and shift schedule, but also wanting a partner physically/emotionally present to share home/social responsibilities. While married firefighters discussed choosing family/home obligations over reducing sleep debt to maintain social/family relationships, single and divorced firefighters spoke of fewer conflicts impeding their ability to prioritize sleep at home.

Conclusion

This study improves our understanding of how work impacts home life in firefighters and can inform future strategies to address work-family conflict and sleep loss concerns, and highlights the importance of managing expectations of time-off to promote a healthier work-life balance.

Support

Oregon Healthy Workforce Center

Circadian Rhythm of Vascular Function in Midlife Adults

Objective- Adverse cardiovascular events occur more frequently in the morning than at other times of the day. Vascular endothelial function (VEF)-a robust cardiovascular risk marker-is impaired during this morning period. We recently discovered that this morning impairment in VEF is not caused by either overnight sleep or the inactivity that accompanies sleep. We determined whether the endogenous circadian system is responsible for this morning impairment in VEF. We also assessed whether the circadian system affects mechanistic biomarkers, that is, oxidative stress (malondialdehyde adducts), endothelin-1, blood pressure, and heart rate. Approach and Results- Twenty-one (11 women) middle-aged healthy participants completed a 5-day laboratory protocol in dim light where all behaviors, including sleep and activity, and all physiological measurements were evenly distributed across the 24-hour period. After baseline testing, participants underwent 10 recurring 5-hour 20-minute behavioral cycles of 2-hour 40-minute sleep opportunities and 2 hours and 40 minutes of standardized waking episodes. VEF, blood pressure, and heart rate were measured, and venous blood was sampled immediately after awakening during each wake episode. Independent of behaviors, VEF was significantly attenuated during the subjective night and across the morning ( P=0.04). Malondialdehyde adducts and endothelin-1 exhibited circadian rhythms with increases across the morning vulnerable period and peaks around noon ( P≤0.01). Both systolic ( P=0.005) and diastolic blood pressure ( P=0.04) were rhythmic with peaks in the late afternoon. Conclusions- The endogenous circadian system impairs VEF and increases malondialdehyde adducts and endothelin-1 in the morning vulnerable hours and may increase the risk of morning adverse cardiovascular events in susceptible individuals. Clinical Trial Registration- URL: http://www.clinicaltrials.gov . Unique identifier: NCT02202811.

Separate and interacting effects of the endogenous circadian system and behaviors on plasma aldosterone in humans

Measurements of aldosterone for diagnosis of primary aldosteronism are usually made from blood sampled in the morning when aldosterone typically peaks. We tested the relative contributions and interacting influences of the circadian system, ongoing behaviors, and prior sleep to this morning peak in aldosterone. To determine circadian rhythmicity and separate effects of behaviors on aldosterone, 16 healthy participants completed a 5-day protocol in dim light while all behaviors ranging from sleep to exercise were standardized and scheduled evenly across the 24-h circadian period. In another experiment, to test the separate effects of prior nocturnal sleep or the inactivity that accompanies sleep on aldosterone, 10 healthy participants were studied across 2 nights: 1 with sleep and 1 with maintained wakefulness (randomized order). Plasma aldosterone was measured repeatedly in each experiment. Aldosterone had a significant endogenous rhythm ( P < 0.001), rising across the circadian night and peaking in the morning (~8 AM). Activity, including exercise, increased aldosterone, and different behaviors modulated aldosterone differently across the circadian cycle (circadian phase × behavior interaction; P < 0.001). In the second experiment, prior nocturnal sleep and prior rested wakefulness both increased plasma aldosterone ( P < 0.001) in the morning, to the same extent as the change in circadian phases between evening and morning. The morning increase in aldosterone is due to effects of the circadian system plus increased morning activities and not prior sleep or the inactivity accompanying sleep. These findings have implications for the time of and behaviors preceding measurement of aldosterone, especially under conditions of shift work and jet lag.

Trouble in transit: Organizational barriers to workers' health

BACKGROUND

Valuable insights on the health and behavior of transit workers can be obtained from qualitative research that considers the social environment, which affects job performance and determines levels of perceived stress.

METHODS

Using a grounded theory approach, semi-structured interviews were conducted with American transit workers (n = 32). Recorded interviews were transcribed and analyzed using a constant comparative method.

RESULTS

Participants described categories related to entrenched organizational practices, particularly managements' leadership style, which created an atmosphere of distrust. High demanding work schedules, as a result of technological advances, were discussed in relation to diminished breaks, fatigue, and unhealthy diets. Transit workers also attributed increased work demands and irregular working hours to compromised time with family and friends.

CONCLUSIONS

The described barriers to positive health behaviors and social support underscore the need for interventions that ensure adequate breaks and recovery between shifts and increase safety for transit passengers. Am. J. Ind. Med. 60:350-367, 2017. © 2017 Wiley Periodicals, Inc.

Mechanisms of stress in the brain

The brain is the central organ involved in perceiving and adapting to social and physical stressors via multiple interacting mediators, from the cell surface to the cytoskeleton to epigenetic regulation and nongenomic mechanisms. A key result of stress is structural remodeling of neural architecture, which may be a sign of successful adaptation, whereas persistence of these changes when stress ends indicates failed resilience. Excitatory amino acids and glucocorticoids have key roles in these processes, along with a growing list of extra- and intracellular mediators that includes endocannabinoids and brain-derived neurotrophic factor (BDNF). The result is a continually changing pattern of gene expression mediated by epigenetic mechanisms involving histone modifications and CpG methylation and hydroxymethylation as well as by the activity of retrotransposons that may alter genomic stability. Elucidation of the underlying mechanisms of plasticity and vulnerability of the brain provides a basis for understanding the efficacy of interventions for anxiety and depressive disorders as well as age-related cognitive decline.

Chronic, noninvasive glucocorticoid administration suppresses limbic endocannabinoid signaling in mice

Limbic endocannabinoid signaling is known to be sensitive to chronic stress; however, studies investigating the impact of prolonged exposure to glucocorticoid hormones have been limited by the concurrent exposure to the stress of daily injections. The present study was designed to examine the effects of a noninvasive approach to alter plasma corticosterone (CORT) on the endocannabinoid system. More precisely, we explored the effects of a 4-week exposure to CORT dissolved in the drinking water of mice (100 μg/ml) and measured cannabinoid CB(1) receptor binding, endocannabinoid content, activity of the endocannabinoid degrading enzyme fatty acid amide hydrolase (FAAH), and mRNA expression of both the CB(1) receptor and FAAH in both the hippocampus and amygdala. Our data demonstrate that CORT decreases CB(1) receptor binding site density in both the hippocampus and amygdala and also reduced anandamide (AEA) content and increased FAAH activity within both structures. These changes in both CB(1) receptor binding and FAAH activity were not accompanied by changes in mRNA expression of either the CB(1) receptor or FAAH in either brain region. Interestingly, our CORT delivery regimen significantly increased 2-AG concentrations within the hippocampus, but not the amygdala. Collectively, these data demonstrate that the confounder of injection stress is sufficient to conceal the ability of protracted exposure to glucocorticoids to reduce CB(1) receptor density and augment AEA metabolism within limbic structures.

Endocrine and physiological changes in response to chronic corticosterone: a potential model of the metabolic syndrome in mouse

Numerous clinical and experimental studies have linked stress to changes in risk factors associated with the development of physiological syndromes, including metabolic disorders. How different mediators of the stress response, such as corticosterone (CORT), influence these changes in risk remains unclear. Although CORT has beneficial short-term effects, long-term CORT exposure can result in damage to the physiological systems it protects acutely. Disruption of this important physiologic signal is observed in numerous disparate disorders, ranging from depression to Cushing's syndrome. Thus, understanding the effects of chronic high CORT on metabolism and physiology is of key importance. We explored the effects of 4-wk exposure to CORT dissolved in the drinking water on the physiology and behavior of male mice. We used this approach as a noninvasive way of altering plasma CORT levels while retaining some integrity in the diurnal rhythm present in normal animals. This approach has advantages over methods involving constant CORT pellets, CORT injections, or adrenalectomy. We found that high doses of CORT (100 microg/ml) result in rapid and dramatic increases in weight gain, increased adiposity, elevated plasma leptin, insulin and triglyceride levels, hyperphagia, and decreased home-cage locomotion. A lower dose of CORT (25 microg/ml) resulted in an intermediate phenotype in some of these measures but had no effect on others. We propose that the physiological changes observed in the high-CORT animals approximate changes observed in individuals suffering from the metabolic syndrome, and that they potentially serve as a model for hypercortisolemia and stress-related obesity.