Associations of allostatic load with sleep apnea, insomnia, short sleep duration, and other sleep disturbances: findings from the National Health and Nutrition Examination Survey 2005 to 2008

Allostatic load in early pregnancy and sleep-disordered breathing

OBJECTIVES

To assess the association between allostatic load in early pregnancy and sleep-disordered breathing (SDB) during pregnancy.

METHODS

High allostatic load in the first trimester was defined as ≥ 4 of 12 biomarkers (systolic blood pressure, diastolic blood pressure, body mass index, cholesterol, low-density lipoprotein, high-density lipoprotein, high sensitivity C-reactive protein, triglycerides, insulin, glucose, creatinine, and albumin) in the unfavorable quartile. SDB was objectively measured using the Embletta-Gold device and operationalized as "SDB ever" in early (6-15 weeks) or mid-pregnancy (22-31 weeks); SDB at each time point was analyzed as secondary outcomes. Multivariable logistic regression was used to test the association between high allostatic load and SDB, adjusted for confounders. Moderation and sensitivity analyses were conducted to assess the role of allostatic load in racial disparities of SDB and obesity affected the relationship between allostatic load and SDB.

RESULTS

High allostatic load was present in 35.0% of the nuMoM2b cohort. The prevalence of SDB ever occurred among 8.3% during pregnancy. After adjustment, allostatic load remained significantly associated with SDB ever (aOR= 5.3; 3.6-7.9), in early-pregnancy (aOR= 7.0; 3.8-12.8), and in mid-pregnancy (aOR= 5.8; 3.7-9.1). The association between allostatic load and SDB was not significantly different for people with and without obesity. After excluding BMI from the allostatic load score, the association decreased in magnitude (aOR= 2.6; 1.8-3.9).

CONCLUSION

The association between allostatic load and SDB was independent of confounders including BMI. The complex and likely bidirectional relationship between chronic stress and SDB deserves further study in reducing SDB.

Sleep and blood pressure variability: A systematic literature review

BACKGROUND

Blood pressure variability (BPV) is a prognostic marker of cardiovascular disease (CVD). Sleep is recognized as a significant risk factor for CVD; however, little is known about the relationship between sleep characteristics and BPV.

OBJECTIVE

In this systematic review, we aimed to (1) describe methods used to measure BPV and sleep and (2) describe the current evidence in the literature on the association between sleep and BPV.

METHODS

A systematic search was conducted using the search terms "sleep" AND ("blood pressure variability" OR "ambulatory blood pressure monitor") in CINAHL, PubMed, Web of Science, and PsycINFO databases.

RESULTS

Twenty-two studies were included in this systematic review. Sleep was measured using various methods, including polysomnography, actigraphy, sleep diaries, and questionnaires, while BPV was measured over various time intervals using different monitoring devices such as a beat-to-beat blood pressure (BP) monitoring device, a 24-h ambulatory BP monitor, or an automatic upper arm BP monitor. The studies demonstrated mixed results on the associations between sleep parameters (sleep quality, architecture, and duration) and increased BPV.

CONCLUSIONS

Although the mechanisms that explain the relationship between sleep and BPV are still unclear, accumulating evidence suggests potential associations between increased BPV with poor sleep quality and longer sleep duration. Given the recent development of sleep and BP monitoring technologies, further research is warranted to assess sleep and BPV under free-living conditions. Such studies will advance our understanding of complex interactions between sleep and CVD risk.

Daytime symptom trajectories among adults with stable heart failure and insomnia: evidence from a randomised controlled trial of cognitive behavioural therapy for insomnia

People with heart failure (HF) experience a high symptom burden and prevalent insomnia. However, little is known about daytime symptom trajectories after cognitive behavioural therapy for insomnia (CBT-I). In this study we describe: (1) daytime symptom trajectories among adults with insomnia and stable HF over 1 year, (2) how symptom trajectories differ between CBT-I versus HF self-management interventions, and (3) associations between demographic, clinical, and sleep characteristics, perceived stress, health-related quality of life (HRQoL), functional performance and daytime symptoms trajectories. We retrospectively analysed data from a randomised controlled trial of CBT-I versus HF self-management (NCT0266038). We measured sleep, perceived stress, HRQoL, and functional performance at baseline and symptoms at baseline, 3, 6, and 12 months. We conducted group-based trajectory modelling, analysis of variance, chi-square, and proportional odds models. Among 175 participants (mean [standard deviation] age 63.0 [12.9] years, 57.1% male, 76% White), we found four daytime symptom trajectories: (A) low improving symptoms (38.3%); (B) low psychological symptoms and high improving physical symptoms (22.8%); (C) high improving symptoms (24.0%); and (D) high not improving symptoms (14.9%). The CBT-I versus the HF self-management group had higher odds of belonging to Group A compared to other trajectories after controlling for baseline fatigue (odds ratio = 3.27, 95% confidence interval 1.39-7.68). The difference between the CBT-I and the HF self-management group was not statistically significant after controlling for baseline characteristics. Group D had the highest body mass index, perceived stress, and insomnia severity and the lowest cognitive ability, HRQoL, and functional performance. Research is needed to further evaluate factors contributing to symptom trajectories.

Longitudinal associations between biopsychosocial stress indicators and sleep in older Puerto Rican adults

OBJECTIVES

To examine the association of biopsychosocial stress indicators (perceived stress, perceived discrimination, stressful life events, and allostatic load) with sleep outcomes (sleep duration and insomnia symptoms) and to examine sex and age interactions for associations between stress and sleep in older Puerto Rican adults.

METHODS

Secondary analyses were performed with 830 participants (72% female) from wave 2 (2006-2011) of the Boston Puerto Rican Health Study (BPRHS), a prospective population-based cohort study (45-75years at baseline) and Boston Puerto Rican Osteoporosis Study (BPROS) (2007-2012), an ancillary study of the BPRHS. Recruitment occurred in randomly selected census blocks using door-to-door and community-based activities. In-home data collection visits included a baseline assessment and follow-up interviews. Questionnaires assessed perceived stress, discrimination, stressful life events, and sleep. Allostatic load indicators were measured objectively. Regression models controlled for sociodemographic, behavioral, and health factors, with interaction analyses, followed by sex- and sex-by-age-stratified analyses.

RESULTS

In the prior 2years, participants with chronic stress had 50% greater odds of reporting nonoptimal sleep duration (<7 or >9 hours). Life events trajectories were significantly related to insomnia symptoms. Men ≥65years who experienced chronic stress had greater insomnia symptoms than women, or than men with low stress or acute stress.

CONCLUSIONS

Stressful life events may affect sleep duration and insomnia symptoms among older Puerto Rican adults, particularly men 65 years and older who experienced chronic stress. Given the differences in sleep patterns experienced by older adults and their relationships with health outcomes, identifying methods to support sleep health among those with chronic stress is important.

Household Food Security Status and Allostatic Load among United States Adults: National Health and Nutrition Examination Survey 2015-2020

BACKGROUND

Household food insecurity has been linked to adverse health outcomes, but the pathways driving these associations are not well understood. The stress experienced by those in food-insecure households and having to prioritize between food and other essential needs could lead to physiologic dysregulations [i.e., allostatic load (AL)] and, as a result, adversely impact their health.

OBJECTIVE

To assess the association between household food security status and AL and differences by gender, race and ethnicity, and Supplemental Nutrition Assistance Program (SNAP) participation.

METHODS

We used data from 7640 United States adults in the 2015-2016 and 2017-March 2020 National Health and Nutrition Examination Survey to estimate means and prevalence ratios (PR) for AL scores (based on cardiovascular, metabolic, and immune biomarkers) associated with self-reported household food security status from multivariable linear and logistic regression models.

RESULTS

Adults in marginally food-secure [mean = 3.09, standard error (SE) = 0.10] and food-insecure households (mean = 3.05; SE = 0.08) had higher mean AL than those in food-secure households (mean = 2.70; SE = 0.05). Compared with adults in food-secure households in the same category, those more likely to have an elevated AL included: SNAP participants [PR = 1.12; 95% confidence interval (CI):  1.03, 1.22] and Hispanic women (PR = 1.20; 95% CI: 1.05, 1.37) in marginally food-secure households; and non-Hispanic Black women (PR = 1.14; 95% CI: 1.03, 1.26), men (PR = 1.13; 95% CI: 1.02, 1.26), and non-SNAP non-Hispanic White adults (PR = 1.22; 95% CI: 1.08, 1.39) in food-insecure households.

CONCLUSIONS

AL may be one pathway by which household food insecurity affects health and may vary by gender, race and ethnicity, and SNAP participation.

Allostatic load and risk of all-cause, cancer-specific, and cardiovascular mortality in older cancer survivors: an analysis of the National Health and Nutrition Examination Survey 1999-2010

Background

Allostatic load has been linked to an increased risk of death in various populations. However, to date, there is no research specifically investigating the effect of allostatic load on mortality in older cancer survivors.

Aims

To investigate the association between allostatic load (AL) and mortality in older cancer survivors.

Method

A total of 1,291 adults aged 60 years or older who survived for ≥1 year since cancer diagnoses were identified from the 1999-2010 National Health and Nutrition Examination Survey. AL was the exposure of interest incorporating 9 clinical measures/biomarkers; one point was added to AL if any of the measures/biomarkers exceeded the normal level. The sum of points was categorized as an ordinal variable to reflect low, moderate, and high AL. Our outcomes of interest were all-cause, cancer-specific, and cardiovascular disease (CVD)-specific mortality. Death was identified by linkage to the National Death Index. Multivariable Cox proportional hazards models were used to estimate adjusted hazard ratio (aHR) and 95% confidence intervals (CI) of mortality by AL category.

Results

Overall, 53.6% of participants were male and 78.4% were white. The mean age of study participants at interview was 72.8 years (SD=7.1). A total of 546 participants died during the follow-up (median follow-up time: 8.0 years). Among them, 158 died of cancer and 106 died of cardiovascular events. Results from multivariable Cox proportional hazards models showed that higher ALS was positively associated with higher all-cause mortality (ALS=4-9 vs. ALS =0-1: aHR=1.52, 95% CI =1.17-1.98, p-trend<0.01) and higher cancer-specific mortality (ALS=4-9 vs. ALS =0-1: aHR=1.80, 95% CI =1.12-2.90, p-trend=0.01). The association between ALS and cardiovascular mortality was positive but non-significant (ALS=4-9 vs. ALS =0-1: aHR=1.59, 95% CI =0.86-2.94, p-trend=0.11).

Conclusions

Our study suggests that older cancer survivors can have a higher risk of death if they have a high burden of AL.

Trajectories in allostatic load as predictors of sleep quality among urban adults: Healthy aging in neighborhoods of diversity across the life span study

OBJECTIVE

/Background: The allostatic framework is a theoretical perspective that identifies allostatic load (AL) as a meaningful measure of dysregulation and desynchrony across biological processes due to cumulative stress exposure, thereby increasing disease risk. Research exploring the relationships of AL with sleep quality have yielded inconsistent findings. We examined AL at three visits (2004-2009 [Visit 1], 2009-2013 [Visit 2] and 2013-2017 [Visit 3]) in relation to sleep quality [Visit 3] among urban adults by sex, race and age group.

PATIENTS/METHODS

We analyzed data on 1489 Healthy Aging in Neighborhoods of Diversity across the Life Span (HANDLS) participants [59.6% female, baseline age: 48.2 years, 58.5% African Americans] with available data on cardiovascular, metabolic and inflammatory AL markers and Pittsburgh Sleep Quality Index (PSQI) scores. Least squares regression models were constructed to evaluate AL score at Visit 1 (AL_v1) and z-transformed probability of higher trajectory in AL score between Visit 1 and Visit 3 (AL_traj) as predictors of PSQI score at Visit 3, controlling for demographic, lifestyle and health characteristics at Visit 1. AL_traj was generated using group-based trajectory modeling.

RESULTS

In fully adjusted models, AL_v1 and PSQI score were positively related among men only (β = 0.43, P = 0.001), whereas higher AL_traj was associated with PSQI score among women (β = 0.51, P = 0.001), White (β = 0.45, P = 0.011) and African American (β = 0.33, P = 0.014) populations. There were no statistically significant interactions according to age group (<50 vs. ≥ 50).

CONCLUSIONS

Disparities exist whereby AL trajectory predicted sleep quality among women irrespective of race and baseline AL predicted sleep quality among men. Future studies should examine bi-directional AL-sleep relationships.

Allostatic load and cardiovascular outcomes in males with prostate cancer

BACKGROUND

Cardiovascular disease (CVD) is the leading cause of death in men with prostate cancer (PC). Accumulated stress plays an important role in CVD development. The cumulative burden of chronic stress and life events can be measured using allostatic load (AL).

METHODS

The initial cohort included males aged 18 years and older diagnosed with PC (2005-2019). AL was modeled as an ordinal variable (0-11). Fine-Gray competing risk regressions measured the impact of precancer diagnosis AL and postdiagnosis AL in 2-year major cardiac events (MACE). The effect of AL changes over time on MACE development was calculated via piecewise Cox regression (before, and 2 months, 6 months, and 1 year after PC diagnosis).

RESULTS

We included 5261 PC patients of which 6.6% had a 2-year MACE. For every 1-point increase in AL before and within 60 days after PC diagnosis, the risk of MACE increased 25% (adjusted hazard ratio [aHR] =1.25, 95% confidence interval [CI] = 1.18 to 1.33) and 27% (aHR = 1.27, 95% CI = 1.20 to 1.35), respectively. Using AL as a time-varying exposure, the risk of MACE increased 19% (aHR = 1.19, 95% CI = 1.11 to 1.27), 22% (aHR = 1.22, 95% CI = 1.14 to 1.33), 28% (aHR = 1.28, 95% CI = 1.23 to 1.33), and 31% (aHR = 1.31, 95% CI = 1.27 to 1.35) for every 1-point increase in AL before, 2 months after, 6 months after, and 1 year after PC diagnosis, respectively.

CONCLUSION

AL and its changes over time are associated with MACE in PC patients, suggesting a role of a biological measure of stress as a marker of CVD risk among men with PC.

Longitudinal association of allostatic load with depressive symptoms among urban adults: Healthy Aging in Neighborhoods of Diversity across the Life Span study

BACKGROUND

Evidence suggests that lifetime exposure to stressful life events and chronic stressors may be linked to geriatric depression. Allostatic load (AL) is considered a mediator of the stress-health relationship and has been linked to psychosocial factors reflecting health disparities. The purpose of this study was to examine the longitudinal associations of AL with depressive symptoms scores among urban adults, before and after stratifying by sex and race.

METHODS

Secondary analyses were performed using Visit 1 (2004-2009), Visit 2 (2009-2013) and Visit 3 (2013-2017) data collected on 2298 Healthy Aging in Neighborhoods of Diversity across the Life Span study participants (baseline age: 30-64 y). AL at Visit 1 (ALv1) and z-transformed probability of higher AL trajectory (ALtraj) between Visits 1 and 3 were calculated using cardiovascular, metabolic and inflammatory risk indicators. The 20-item Center for Epidemiologic Studies Depression (CES-D) scale was used to calculate total and domain-specific depressive symptoms scores. Mixed-effects linear models controlled for socio-demographic, lifestyle and health characteristics.

RESULTS

In fully adjusted models, a positive cross-sectional relationship was observed between ALv1 and "somatic complaints" depressive symptoms (β = 0.21, P = 0.006) score at Visit 1, whereas ALtraj was associated with increasing depressive symptoms score (β = 0.086, P = 0.003) between Visits 1 and 3. An inverse relationship was observed between ALtraj and "positive affect" depressive symptoms score at Visit 1 among women (β = -0.31, P < 0.0001) and White adults (β = -0.32, P = 0.004). Among women, ALtraj was also positively related to change in "somatic complaints" depressive symptoms score between Visits 1 and 3 (β = 0.043, P = 0.020).

CONCLUSIONS

Among urban adults, AL may be associated with "somatic complaints" depressive symptoms at baseline. Higher AL trajectories may predict increasing depressive symptoms (overall) and increasing "somatic complaints" depressive symptoms (among women). A higher AL trajectory may be associated with lower "positive affect" depressive symptoms at baseline among women and White adults only.

Minority stress and sleep: How do stress perception and anxiety symptoms act as mediators for sexual minority men?

OBJECTIVES

Sexual minority men experience worse sleep than heterosexuals. Little is known about how minority stress may account for these differences. Therefore, the aims of this study are to (1) understand the relationship between minority stress and sleep disturbance in a sample of sexual minority men, and (2) test whether these relationships are mediated by generalized anxiety symptoms and perception of stress.

METHODS

In 2020, 239 sexual minority men were recruited to complete an online survey. Participants responded to scales assessing minority stress (ie, internalized homophobia, experiences of harassment, microaggressions), perception of stress, generalized anxiety symptoms, and sleep disturbance. Linear regressions were used to test the relationship between minority stress and sleep disturbance and to test generalized anxiety symptoms and perception of stress as mediators.

RESULTS

The final model was significant (F = 16.916, p < .001) and accounted for 43.5% of the variance in sleep disturbance. Generalized anxiety symptoms and perception of stress fully mediated the relationships between minority stress and sleep disturbance.

CONCLUSIONS

Findings from this study suggest the need for psychological intervention to improve sleep for sexual minority men. Future research should test this model longitudinally, and include objective measures of stress. Future interventions could target stress perception using mindfulness or cognitive-based interventions.

Preliminary Evidence for the Sequentially Mediated Effect of Racism-Related Stress on Pain Sensitivity Through Sleep Disturbance and Corticolimbic Opioid Receptor Function

Sleep disturbance predicts worse pain outcomes. Because sleep disturbance inequitably impacts Black adults - with racism as the upstream cause - understanding how racism-related stress impacts pain through sleep might help minimize racialized pain inequities. This preliminary study examined sequential mediation of the effect of racism-related stress on experimental pain through sleep disturbance and corticolimbic μOR function in pain-free non-Hispanic Black (NHB) and White (NHW) adults. Participants completed questionnaires, actigraphy, positron emission tomography, and sensory testing. We reproduced findings showing greater sleep disturbance and pain sensitivity among NHB participants; greater sleep disturbance (r = .35) and lower pain tolerance (r=-.37) were significantly associated with greater racism-related stress. In a sequential mediation model, the total effect of racism-related stress on pain tolerance (β=-.38, P = .005) weakened after adding sleep disturbance and ventromedial prefrontal cortex (vmPFC) μOR binding potential (BPND) as mediators (β = -.18, P = .16). The indirect effect was statistically significant [point estimate = -.003, (-.007, -.0003). Findings showed a potential sequentially mediated effect of racism-related stress on pain sensitivity through sleep disturbance and vmPFC μOR BPND. As policy efforts are enacted to eliminate the upstream cause of systemic racism, these results cautiously suggest that sleep interventions within racism-based trauma informed therapy might help prevent downstream effects on pain. PERSPECTIVE: This preliminary study identified the effect of racism-related stress on pain through sleep disturbance and mu-opioid receptor binding potential in the ventromedial prefrontal cortex. Findings cautiously support the application of sleep interventions within racism-based trauma-informed therapy to prevent pain inequities as policy changes function to eliminate all levels of racism.

Allostatic Load and Cognitive Function Among Urban Adults in the Healthy Aging in Neighborhoods of Diversity across the Life Span Study

BACKGROUND

Cross-sectional studies have linked cognition to allostatic load (AL) which reflects multisystem dysregulation from life course exposure to stressors.

OBJECTIVE

To examine baseline and changes in AL and their relationships with 11 cognitive function test scores, while exploring health disparities according to sex and race.

METHODS

Longitudinal [Visit 1 (2004-2009) and Visit 2 (2009-2013)] data were analyzed from 2,223 Healthy Aging in Neighborhoods of Diversity across the Life Span participants. We calculated AL total score using cardiovascular, metabolic, and inflammatory risk indicators, and applied group-based trajectory modeling to define AL change.

RESULTS

Overall and stratum-specific relationships were evaluated using mixed-effects linear regression models that controlled for socio-demographic, lifestyle, and health characteristics. Baseline AL was significantly associated with higher log-transformed Part A Trail Making Test score [Loge (TRAILS A)] (β= 0.020, p = 0.004) and increasing AL was associated with higher Benton Visual Retention Test score [BVRT] (β= 0.35, p = 0.002) at baseline, in models that controlled for age, sex, race, poverty status, education, literacy, smoking, drug use, the 2010 healthy eating index and body mass index. Baseline AL and AL change were not related to change in cognitive function between visits. There were no statistically significant interaction effects by sex or race in fully-adjusted models.

CONCLUSION

At baseline, AL was associated with worse attention or executive functioning. Increasing AL was associated with worse non-verbal memory or visuo-constructional abilities at baseline. AL was not related to change in cognitive function over time, and relationships did not vary by sex or race.

Allostatic Load Measurement: A Systematic Review of Reviews, Database Inventory, and Considerations for Neighborhood Research

BACKGROUND

Neighborhoods are critical to understanding how environments influence health outcomes. Prolonged environmental stressors, such as a lack of green spaces and neighborhood socioeconomic disadvantage, have been associated with higher allostatic load levels. Since allostatic load levels experienced earlier in life have stronger associations with mortality risk, neighborhoods may be uniquely suited to monitor and mitigate the impacts of environmental stressors. Researchers often study allostatic load in neighborhoods by utilizing administrative boundaries within publicly accessible databases as proxies for neighborhoods.

METHODS

This systematic review of reviews aims to identify commonly used biomarkers in the measurement of allostatic load, compare measurement approaches, inventory databases to study allostatic load, and spotlight considerations referenced in the literature where allostatic load is studied in neighborhoods. The review was conducted using the search term "allostatic load" in the MEDLINE, CINAHL, and PsychINFO databases. The search results were filtered to include reviews.

RESULTS

The search returned 499 articles after deduplication. Overall, 18 synthesis reviews met the inclusion criteria and were retained for extraction. The synthesis reviews analyzed represented 238 studies published from 1995 to 2020. The original ten biomarkers were most often used to measure allostatic load. More recently, body mass index and C-reactive protein have additionally been frequently used to measure allostatic load burden.

CONCLUSIONS

The scientific contributions of this study are that we have identified a clear gap in geographic considerations when studying allostatic load. The implication of this study is that we have highlighted geographic concepts when conducting neighborhood-level research using administrative databases as a neighborhood proxy and outlined emerging future trends that can enable future study of allostatic load in the neighborhood context.

Measuring allostatic load: Approaches and limitations to algorithm creation

OBJECTIVE

Allostatic load literature has proliferated over the past three decades, and a growing body of research demonstrates that higher levels of allostatic load are associated with a wide range of negative physical and mental health outcomes. However, there remain significant challenges with operationalization of the concept. A scoping review of the methods employed to create an allostatic load algorithm was conducted and recommendations for future research with an orientation towards advancing clinical application of the theory are discussed.

METHODS

A search of seven electronic databases (PubMed, PsycINFO, Social Work Abstracts, Social Service Abstracts, Social Sciences Citation Index (Web of Science), Sociological Abstracts, Scopus) was completed with the search term "allostatic load." Studies were reviewed, and if they met the inclusion criteria, data was extracted, complied, and presented in the narrative, table, and figures.

RESULTS

The initial searches yielded 5280 results with the final sample of 395 non-duplicate articles that met the inclusion criteria. More than half (52.5%) of all included publications employed biomarker cutoffs based on the high-risk quartiles of the sample distribution, 11.1% employed the sum of at-risk clinical scores, and the remainder of studies utilized a range of different algorithms.

CONCLUSION

Allostatic load literature has grown at an exponential rate in recent years, but researchers continue to operationalize the concept via algorithms that may have limited utility moving forward. More nuanced statistical approaches are emerging and should be considered, as should a shift towards an approach that can provide additional clinical utility.

Towards A Socioeconomic Model of Sleep Health among the Canadian Population: A Systematic Review of the Relationship between Age, Income, Employment, Education, Social Class, Socioeconomic Status and Sleep Disparities

A better understanding of the contribution of the socioeconomic status (SES) in sleep health could guide the development of population-based interventions aiming to reduce “the silent public health issue” that are sleep disturbances. PRISMA was employed to identify relevant studies having examined the association between social class, social capital, education, income/assets, occupation/employment status, neighborhood deprivation and sleep health. Sixteen cross-sectional and three longitudinal studies were selected, having sampled 226,029 participants aged from 2 months to 85 years old. Findings showed that: (1) sleep health disparities among children and adolescent are strongly correlated to parental socioeconomic indicators; (2) poor parental income, poor family SES and poor parental education are associated with higher sleep disturbances among children and adolescents; (3) lower education is a predictor of increased sleep disturbances for adults; (4) low SES is associated with high sleep disturbances in adults and old people and; (5) low income and full-time employment was significantly associated with short sleep among adults and old people. In conclusion, sleep health should be an important public health target. Such intervention would be beneficial for populational health, for all taxpayers and public administrations, which would see a reduction in absenteeism and productivity losses attributable to sleep-related health problems in the global economy.

Systematic review: sleep health in the US Latinx population

Sleep disturbances are a common and unmet health problem in Latinx. While Latinx report similar sleep disturbances as non-Hispanic Whites [NHW], Latinx suffer from these disturbances to a greater degree than their NHW counterparts. Sleep disturbances are associated with increased risk of chronic health conditions, which Latinx experience at high rates. Research also points to significant sleep differences within Latinx. Given that Latinx are a rapidly growing population in the United States, sleep disparities between Latinx and NHWs and sleep differences within Latinx warrant further investigation. While research on Latinx sleep is growing, the last narrative review on US Latinx sleep health was published by Loredo and colleagues in 2010. Our narrative review expands on Loredo et al.'s work, adding the literature on Latinx sleep published since 2010 (N = 70). A total of 78 peer-reviewed articles related to young to middle-aged (i.e., 18-65 years) healthy Latinx adult sleep were identified in three databases-PsycInfo, PubMed/Medline, and Web of Science. With the socioecological model as framework, this review (1) summarizes current evidence pertaining to sleep health in healthy, community dwelling, urban Latinx adults; (2) discusses measurement challenges related to investigating Latinx sleep disparities and differences; and (3) discusses potential contributors to Latinx sleep. The prevalence of short sleep duration, long sleep duration, and poor sleep quality is high among Latinx; there are differences by Latinx subgroup. Our review identifies several multi-level influences associated with poor sleep: SES, sexual minority status, racial discrimination, access to care, neighborhood environment, and shift work. N = 250/250.

Risk of COPD exacerbation is increased by poor sleep quality and modified by social adversity

STUDY OBJECTIVES

Sleep is an important dimension in the care of chronic obstructive pulmonary disease (COPD), but its relevance to exacerbations is unclear. We wanted to assess whether sleep quality as measured by the Pittsburgh Sleep Quality Index (PSQI) is associated with an increased risk of COPD exacerbations and does this differ by socio-environmental exposures.

METHODS

We included 1647 current and former smokers with spirometrically confirmed COPD from the SPIROMICS cohort. We assessed incidence rate ratios for exacerbation using zero-inflated negative binomial regression adjusting for demographics, medical comorbidities, and multiple metrics of disease severity, including respiratory medications, airflow obstruction, and symptom burden. Our final model adjusted for socio-environmental exposures using the Area Deprivation Index, a composite measure of contemporary neighborhood quality, and Adversity-Opportunity Index, a composite measure of individual-level historic and current socioeconomic indicators. We used a pre-determined threshold of 20% missingness to undertake multiple imputation by chained equations. As sensitivity analyses, we repeated models in those with complete data and after controlling for prior exacerbations. As an exploratory analysis, we considered an interaction between socio-environmental condition and sleep quality.

RESULTS

After adjustment for all co-variates, increasing PSQI scores (range 0-21) were associated with a 5% increased risk for exacerbation per point (p = .001) in the imputed dataset. Sensitivity analyses using complete cases and after controlling for prior exacerbation history were similar. Exploratory analysis suggested less effect among those who lived in poor-quality neighborhoods (p-for-interaction = .035).

CONCLUSIONS

Poor sleep quality may contribute to future exacerbations among patients with COPD. This represents one target for improving disease control.

CLINICAL TRIAL REGISTRATION

Subpopulations and Intermediate Outcome Measures in COPD Study (SPIROMICS). ClinicalTrials.gov Identifier# NCT01969344. Registry URL: https://clinicaltrials.gov/ct2/show/.

Mediating role of psychological distress in the associations between neighborhood social environments and sleep health

STUDY OBJECTIVES

The characteristics of neighborhood social environments, such as safety and social cohesion, have been examined as determinants of poor sleep. The current study investigates associations between neighborhood social characteristics and sleep health, as well as the mediating role of psychological distress on these possible associations.

METHODS

Three waves of PHRESH Zzz (n = 2699), a longitudinal study conducted in two low-income, predominately Black neighborhoods, were utilized for this analysis. The characteristics of neighborhood social environments were measured using crime rates, a neighborhood social disorder index, and self-reported social cohesion. Sleep health was measured via 7 days of wrist-worn actigraphy as insufficient sleep, sleep duration, wake after sleep onset (WASO), and sleep efficiency. G-estimations based on structural nested mean models and mediation analyses were performed to estimate the effects of neighborhood social environments on sleep as well as direct/indirect effects through psychological distress.

RESULTS

Crime rate around residential addresses was associated with increased risk of insufficient sleep (risk ratio: 1.05 [1.02, 1.12]), increased WASO (β: 3.73 [0.26, 6.04]), and decreased sleep efficiency (β: -0.54 [-0.91, -0.09]). Perceived social cohesion was associated with decreased risk of insufficient sleep (OR: 0.93 [0.88, 0.97]). Psychological distress mediated part of the associations of crime and social cohesion with insufficient sleep.

CONCLUSIONS

Neighborhood social environments may contribute to poor sleep health in low-income, predominantly Black neighborhoods, and psychological distress can be a salient pathway linking these neighborhood characteristics and sleep health.

Allostatic Load, Single, and Dual Chronic Conditions: Evidence from the National Health and Nutrition Examination Survey

Background:

Allostatic load (AL) is defined as a cumulative burden of chronic stress and life events, which involves the interaction of different physiological systems at varying degrees of activity. AL is suspected of contributing to health disparities among different populations. Suppressed or overactive physiological systems can interrupt AL affecting proper tissue and organ function leading to disease. The objective of our study was to determine the association of AL with dual chronic conditions.

Methods:

We used data from the National Health and Nutrition Examination Survey (NHANES). For the current analysis, we used the data cycles of 2007–2010, which is the most recent data that collected comprehensive measures of the composite AL outcome variable. Descriptive, bivariate, and multivariable logistic regression, with stepwise forward variable selection method (P < 0.05), were conducted using STATA/IC 15.0.

Results:

AL levels were high among 20% of the respondents (n = 2179). Having a lower income to poverty ratio, being married, physical inactivity, experiencing sleep problems, and a history of smoking were significantly associated with high AL (P < 0.05). Non-Hispanic blacks [odds ratio (OR): 1.8; 95% confidence interval (CI): 1.6–2.4] and Mexicans and other Hispanics (OR: 1.4; 95% CI: 1.1–1.7) had higher AL compared to Caucasians. Having cardiovascular disease (CVD) (OR: 1.7; 95% CI: 1.4–2.2) and diabetes (OR: 4.7; 95% CI: 3.8–5.7) independently, as well as both CVD and diabetes (OR: 3.1; 95% CI 2.7–3.6), were associated with higher odds of AL. We conducted an age-adjusted regression model that indicated higher odds of elevated AL among females with diabetes independently (OR: 1.4; 95% CI: 1.2–1.9) and with both CVD and diabetes (OR: 1.6; 95% CI: 1.2–2.1) compared to men.

Conclusions:

Despite the significant impact and association of AL with overall health, there is minimal evidence of its risk factors and linkage to disease burden. Modifiable lifestyle factors were associated with a higher AL. There is a critical need to support ethnic and gender contextual interventions to reduce the burden of AL on chronic conditions.

Variables Impacting the Quality of Life of Dementia Caregivers: A Data Visualization Analysis

PURPOSE

Visually explore the rates of and relationships between overall physical and mental health, sleep disturbances, and depression rates in a single sample of caregivers of persons with dementia, caregivers of persons with other chronic illness, and non-caregiving adults.

DESIGN

Exploratory descriptive study utilizing data visualization methods.

METHODS

Data were analyzed from the 2017 Behavioral Risk Factor Surveillance System dataset. Multiple graphs and charts were developed to visualize data between groups. Descriptive statistics analyzed the rates of variables of interest across the three groups. One-way analysis of variance assessed relationships between variables.

RESULTS

Caregivers of persons with dementia and of other chronic illnesses reported poorer health outcomes as compared to non-caregiving adults. However, caregivers of persons with other chronic illnesses reported the worst outcomes of all groups. Depression and sleep disturbances were prevalent in all three groups.

CONCLUSIONS

The quality of life of caregivers of persons with dementia and chronic illness is impacted by poorer health outcomes, specifically mental health and sleep.

CLINICAL RELEVANCE

Findings support the need for caregiver-specific interventions that target overall physical and mental health, depression, and sleep disturbances. However, we also found support for mental health and sleep interventions for all individuals.

Environmental Influences on Sleep in the California Teachers Study Cohort

Only two-thirds of Americans meet the recommended 7 hours of sleep nightly. Insufficient sleep and circadian disruption have been associated with adverse health outcomes, including diabetes and cardiovascular disease. Several environmental disruptors of sleep have been reported, such as artificial light at night (ALAN) and noise. These studies tended to evaluate exposures individually. We evaluated several spatially derived environmental exposures (ALAN, noise, green space, and air pollution) and self-reported sleep outcomes obtained in 2012-2015 in a large cohort of 51,562 women in the California Teachers Study. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated for sleep duration and latency. After adjusting for age, race/ethnicity, chronotype, use of sleep medication, and self-reported trouble sleeping, ALAN (per 5 millicandela (mcd)/m2 luminance, OR = 1.13, 95% CI: 1.07, 1.20) and air pollution (per 5 μg/m3 PM2.5, OR = 1.06, 95% CI: 1.04, 1.09) were associated with shorter sleep duration (<7 hours), and noise was associated with longer latency (>15 minutes) (per 10 decibels, OR = 1.05, 95% CI: 1.01, 1.10). Green space was associated with increased duration (per 0.1 units, OR = 0.41, 95% CI: 0.28, 0.60) and decreased latency (per 0.1 units, OR = 0.55, 95% CI: 0.39, 0.78). Further research is necessary to understand how these and other exposures (e.g., diet) perturb an individuals' inherited sleep patterns and contribute to downstream health outcomes.

Sleep behavior of New York City taxi drivers compared to the general US population

Introduction

Taxi drivers are a low income population with long work hours, a high-stress sedentary occupation, and varied work shifts, augmenting their risk for sleep disorders. We evaluated sleep quality among New York City (NYC) taxi drivers, a predominantly immigrant/minority population, for associations with sleep outcomes and examined intervention development and policy implications.

Methods

A cross-sectional survey was conducted at driver-frequented locations with 211 consenting NYC taxi drivers and included the 12-item Medical Outcomes Study Sleep Scale and the Perceived Stress Scale-10. For five domains (sleep disturbance, snoring, shortness of breath, sleep adequacy, and somnolence) and Sleep Problems Index-II, self-reported scores were calculated and normed against a nationally representative 2009 US sample to obtain standardized t-test scores. Scores <47 were lower than US averages, indicating worse sleep quality. Results were explored in multivariable linear and logistic regression models.

Results

Almost one-half (47%) of drivers had scores indicating sleep quality below US averages for snoring, 36% for shortness of breath/obstruction, and 19% for somnolence. There were significant associations of perceived stress with Sleep Problems Index II (p<0.001), sleep disturbance (p<0.001), somnolence (p<0.001), and sleep adequacy (p<0.05). Stress was predictive of sleep adequacy (p<0.05, bivariate; p<0.05, multivariate) and shortness of breath/obstruction (p<0.01, bivariate; p<0.001, multivariate). Nightshift drivers had significantly worse sleep disturbance scores than dayshift drivers (p<0.05). Taxi drivers were more likely to get an inadequate amount of daily sleep (<7 hours) than the average US male (48.5% vs. 38.3%).

Conclusions

Sleep hygiene and stress management interventions could benefit the health of this population and improve driver and public safety. The associations of taxi driver sleep quality and stress indicate an opportunity for targeted intervention. Further research into sleep as an important determinant of taxi driver health is needed, especially in the burgeoning for-hire vehicle (Uber, Lyft, etc) sector.

Association between health behaviours and cardiometabolic dysregulation: a population-based survey among healthy adults in Hong Kong

OBJECTIVE

To explore the association between cardiometabolic dysregulation, an integral component of allostatic load, and health risk behaviours (HRBs) of the Hong Kong healthy adult population.

DESIGN

Secondary analysis of cross-sectional anonymous data.

SETTING

Data on sociodemographics, self-reported health status, HRBs and biomarkers were extracted from the Hong Kong Population Health Survey 2014/2015.

PARTICIPANTS

One thousand five hundred and fifty-one participants aged 18-64 years without self-reported diagnoses of hypertension, diabetes mellitus, hyperlipidaemia, cardiovascular disease, cognitive impairment or cancer.

PRIMARY OUTCOME MEASURES

Cardiometabolic dysregulation index (CMDI), ranging from 0 to 6, was calculated by counting the number of biomarkers including systolic blood pressure, diastolic blood pressure, waist to hip ratio, glycated haemoglobin, total cholesterol to high-density lipoprotein cholesterol ratio, and triglycerides that were above the respective normal level suggested by international guidelines and literature. HRBs including smoking, dietary habits and sleeping hours were collected by self-report questionnaire. Alcohol consumption was assessed by the 10-item Alcohol Use Disorders Identification Test, while physical activity level was measured using the Global Physical Activity Questionnaire. A composite HRB score, ranging from 0 to 5, was calculated as the cumulative number of HRBs. The effect of HRB on CMDI was evaluated by negative binomial regression with adjustment for socioeconomic status, health awareness and comorbidities of the participants.

RESULTS

The mean CMDI of the studied population was 1.6; 29.5% had a CMDI of 0, whereas 1.5% had a CMDI of 6. Significant difference was observed in mean CMDI between gender and different age groups. Sleeping less than 6 hours (incidence rate ratio (IRR)=1.26, p<0.001), smoking (IRR=1.15, p=0.027), insufficient physical activity (IRR=1.12, p=0.007) and higher composite HRB score (IRR=1.12, 95% CI 1.06 to 1.18) were significantly associated with higher CMDI.

CONCLUSION

Smoking, physical inactivity and inadequate sleep-an essential yet often overlooked health behaviour-were associated with higher CMDI in the Hong Kong healthy adult population.

Socioeconomic status and sleep disturbances among pediatric population: a continental systematic review of empirical research

To this day, no consensus has been established on the definition and the conceptualization of the socioeconomic status (SES), since all the available studies on the relation between SES and health did not use the same conceptual framework and operationalization to assess SES. While literature reported that SES markers (such as income, social support networks, education, employment or occupation) influence the health of populations by shaping living conditions; empirical research does not tell us which SES markers affect more strongly the sleep components of the individuals, as well as which sleep disorders (SD) are affected and how. Even though several original studies have tried to assess how changes in socioeconomic status of parents may affect the psychosocial environment and mental health of an individual directly or through his community, no systematic reviews on the influence of SES on children's sleep are available. This systematic review make an update on the different measures of SES and sleep disturbances used for pediatric population across the different regions of the world. Recommendations for a future standardization of SES measures is proposed, for a better understanding of its influence on sleep disturbances.

Exploring the Relationship Between Substance Use and Allostatic Load in a Treatment/Research Cohort and in a US Probability Sample (NHANES 2009-2016)

Allostatic load, an operationalization for cumulative strain on physiology from adaptation (allostasis) to stress over a lifetime, can manifest as damage to cardiovascular, neuroendocrine, and metabolic systems. The concept of allostatic load may be particularly useful in research on substance-use disorders (SUDs) because SUD researchers have sought to better understand the relationship between chronic stressors and drug use. Theoretical models hold that SUDs can be conceptualized as a spiral toward a state of persistent allostasis (i.e., allostasis so persistent as to represent homeostasis at a new, unhealthy set point). Regardless of the extent to which those models are accurate, increased allostatic load could be a mechanism by which frequent drug administration increases risk for adverse outcomes. We conducted two secondary analyses to evaluate allostatic load in the context of drug use, including alcohol use, in a locally recruited sample with a high proportion of illicit substance use (N = 752) and in a nationally representative sample from the NHANES 2009-2016. We hypothesized that after controlling for age and other potential confounds, people with longer histories of drug use would have higher allostatic-load scores. Multiple regression was used to predict allostatic load from participants' drug-use histories while controlling for known confounds. In the locally recruited sample, we found that longer lifetime use of cocaine or opioids was related to increased allostatic load. In NHANES 2009-2016, we found few or no such associations. Lengthy histories of problematic non-medical substance use may facilitate more rapid increases in allostatic load than aging alone, and, together with findings from previous investigations, this finding suggests increased risk for chronic disease.

Allostatic load and women's brain health: A systematic review

Allostatic load represents the 'wear and tear' of chronic stress on the brain and body that may differ between men and women. A small but growing number of studies are assessing allostatic load in relation to mental health. The objective of this systematic review was to (1) assess sex differences in allostatic load and (2) identify allostatic load associations that are specific to women. We systematically searched for allostatic load studies that included psychosocial causes and/or psychiatric consequences. Our search focused on allostatic load studies that disaggregated by sex and that include women. Sixty-two studies were included in this systematic review. First, men appear to have higher allostatic load than women. Second, women show gender-specific variation for numerous factors such as age, race/ethnicity, adversities, social support, and health behaviors that influence associations between allostatic load and mental health. Recommendations are made to guide researchers advance sex and gender approaches.

Pre-diagnostic allostatic load and health-related quality of life in a cohort of Black breast cancer survivors

PURPOSE

To determine the association of pre-diagnostic allostatic load (AL) with health-related quality of life (HRQOL) among Black women with breast cancer.

METHODS

In a sample of 409 Black women with non-metastatic breast cancer enrolled in the Women's Circle of Health Follow-Up Study (WCHFS), two pre-diagnostic AL measures were estimated using medical records data from up to 12 months prior to breast cancer diagnosis: AL-lipid/metabolic profile-based measure and AL-inflammatory profile-based measure. HRQOL was assessed approximately 24 months post diagnosis, using the Functional Assessment of Cancer Therapy-Breast Cancer (FACT-B) instrument, including 5 subscale scores [presented by physical well-being (PWB), social & family well-being (SFWB), emotional well-being (EWB), functional well-being (FWB), and breast cancer-specific scale (BCS)] and 3 derived total scores [presented by trial outcome index (TOI), Functional Assessment of Cancer Therapy-General (FACT-G) and FACT-B]. We used multivariable logistic regression models, using dichotomized AL scores (lower AL: 0-3 points, higher AL: 4-8 points), to assess the associations between the two pre-diagnostic AL measures and HRQOL.

RESULTS

Higher pre-diagnostic AL was associated with poorer FWB and lower FACT-G, but these associations were statistically significant for the AL-inflammatory profile-based measure (FWB: OR 1.63, 95% CI 1.04, 2.56; FACT-G: OR 1.62, 95% CI 1.04, 2.54), but not the AL-lipid/metabolic profile-based measure (FWB: OR 1.45, 95% CI 0.81, 2.59; FACT-G: OR 1.33, 95% CI 0.75, 2.37).

CONCLUSION

These findings suggest that higher AL, particularly when measured using the inflammatory profile-based measure, was associated with poorer HRQOL, namely FWB and FACT-G, among Black breast cancer survivors.

Interaction of Sleep and Cortical Structural Maintenance From an Individual Person Microlongitudinal Perspective and Implications for Precision Medicine Research

Sleep and maintenance of brain structure are essential for the continuity of a person's cognitive/mental health. Interestingly, whether normal structural maintenance of the brain and sleep continuously interact in some way over day-week-month times has never been assessed at an individual-person level. This study used unconventional microlongitudinal sampling, structural magnetic resonance imaging, and n-of-1 analyses to assess normal interactions between fluctuations in the structural maintenance of cerebral cortical thickness and sleep duration for day, week, and multi-week intervals over a 6-month period in a healthy adult man. Correlation and time series analyses provided indications of "if-then," i.e., "if" this preceded "then" this followed, sleep-to-thickness maintenance and thickness maintenance-to-sleep bidirectional inverse interactions. Inverse interaction patterns were characterized by concepts of graded influences across nights, bilaterally positive relationships, continuity across successive weeks, and longer delayed/prolonged effects in the thickness maintenance-to-sleep than sleep-to-thickness maintenance direction. These interactions are proposed to involve normal circadian/allostatic/homeostatic mechanisms that continuously influence, and are influenced by, cortical substrate remodeling/turnover and sleep/wake cycle. Understanding interactions of individual person "-omics" is becoming a central interest in precision medicine research. The present n-of-1 findings contribute to this interest and have implications for precision medicine research use of a person's cortical structural and sleep "-omics" to optimize the continuous maintenance of that individual's cortical structure, sleep, and cognitive/mental health.

Household Food Insecurity and the Association with Cumulative Biological Risk among Lower-Income Adults: Results from the National Health and Nutrition Examination Surveys 2007-2010

Household food insecurity has been associated with adverse health outcomes; however, the mechanisms underlying these associations are not well-defined. Using data from 5005 adults from the 2007-2010 National Health and Nutrition Examination Surveys (NHANES), we examined associations between household food insecurity and cumulative biological risk, a measure of the body's physiological response to chronic stress. Household food security was assessed using the 18-item Household Food Security Survey Module. Marginal food security refers to 1-2 positive responses, and food insecurity refers to ≥3 positive responses. The cumulative biological risk scores were calculated based on the distributions of ten biomarkers from the cardiovascular, metabolic, and immune systems. Elevated biological risk was defined as a risk score of ≥3. Multivariable regression models were used to examine associations between food security and cumulative biological risk scores, adjusting for sociodemographic characteristics. After multivariable adjustment, food insecurity was associated with a 0.14-unit higher cumulative biological risk score (95% CI 0.05-0.22, p-trend = 0.003) and higher odds of elevated biological risk (OR 1.20, 95% CI 1.05-1.37, p-trend = 0.003). These associations differed by gender. Among women, food insecurity was associated with 0.30-unit higher cumulative biological risk score (95% CI 0.14-0.45, p-trend = 0.0004) and higher odds of elevated biological risk (OR 1.61, 95% CI 1.29-2.00, p-trend < 0.0001). These associations were not observed in men. Women experiencing food insecurity demonstrated elevated levels of biological risk. These findings support the hypothesis that food insecurity may be associated with women's chronic health outcomes through the pathway of chronic stress. Further research is needed to understand why these associations were not observed in men.

Trends in the use of medications with insomnia side effects and the implications for insomnia among US adults

Americans are increasingly consuming pharmaceuticals that although effective in treating their focal indication, include insomnia as a side effect. Regardless, no studies have documented trends in the concurrent use of these medications and their implications for insomnia among community-dwelling adults. Using a nationally representative sample of US adults from the 1999-2016 National Health and Nutrition Examination Survey (NHANES), this study shows that the concurrent use of medications with insomnia as a potential side effect ("insomnia side effects" hereafter) has increased considerably in the past two decades. Between 1999 and 2016, the use of one and two or more medications with insomnia side effects increased by 66% and 164%, respectively. Compared to non-users, respondents who took two or more of these medications were more likely to report insomnia symptoms (odds ratio [OR] = 1.78; 95% confidence interval [CI], 1.22 to 2.60), daytime sleepiness symptoms (OR = 1.73; 95% CI, 1.16 to 2.60) and difficulty with at least two daytime activities due to sleepiness or tiredness (OR = 1.96; 95% CI, 1.28 to 3.00). These findings highlight the need for insomnia screenings among patients who consume medications with insomnia side effects. They also emphasize the increased risks of insomnia associated with polypharmacy.

Allostatic Load Indices With Cholesterol and Triglycerides Predict Disease and Mortality Risk in Zoo-Housed Western Lowland Gorillas (Gorilla gorilla gorilla)

Allostatic load, or the physiological dysregulation accumulated due to senescence and stress, is an established predictor of human morbidity and mortality and has been proposed as a tool for monitoring health and welfare in captive wildlife. It is estimated by combining biomarkers from multiple somatic systems into allostatic load indices (ALIs), providing a score representing overall physiological dysregulation. Such ALIs have been shown to predict disease and mortality risk in western lowland gorillas. In these prior analyses, we were unable to include lipid markers, a potential limitation as they are key biomarkers in human models. Recently, we were able to assay serum cholesterol and triglycerides and add them to our previous ALI. We then re-examined associations with health outcomes using binomial generalized linear models. We constructed ALIs using 2 pooling strategies and 2 methods. By itself, a 1-unit increase in allostatic load was associated with higher odds of all-cause morbidity and mortality, but results were mixed for cardiac disease. However, the best fit models for all-cause morbidity and cardiac disease included only age and sex. Allostatic load was retained alongside age in the best fit models for mortality, with a 1-unit increase associated with 23% to 45% higher odds of death. Compared with previous results, ALIs containing cholesterol and triglycerides better predict disease risk in zoo-housed western lowland gorillas, as evidenced by larger effect sizes for some models and better goodness of fit for all ALIs. Based on these results, we address methodology for future allostatic load research on wildlife.

Bidirectional relationship between sleep and Alzheimer's disease: role of amyloid, tau, and other factors

As we age, we experience changes in our nighttime sleep and daytime wakefulness. Individuals afflicted with Alzheimer's disease (AD) can develop sleep problems even before memory and other cognitive deficits are reported. As the disease progresses and cognitive changes ensue, sleep disturbances become even more debilitating. Thus, it is imperative to gain a better understanding of the relationship between sleep and AD pathogenesis. We postulate a bidirectional relationship between sleep and the neuropathological hallmarks of AD; in particular, the accumulation of amyloid-β (Aβ) and tau. Our research group has shown that extracellular levels of both Aβ and tau fluctuate during the normal sleep-wake cycle. Disturbed sleep and increased wakefulness acutely lead to increased Aβ production and decreased Aβ clearance, whereas Aβ aggregation and deposition is enhanced by chronic increased wakefulness in animal models. Once Aβ accumulates, there is evidence in both mice and humans that this results in disturbed sleep. New findings from our group reveal that acute sleep deprivation increases levels of tau in mouse brain interstitial fluid (ISF) and human cerebrospinal fluid (CSF) and chronic sleep deprivation accelerates the spread of tau protein aggregates in neural networks. Finally, recent evidence also suggests that accumulation of tau aggregates in the brain correlates with decreased nonrapid eye movement (NREM) sleep slow wave activity. In this review, we first provide a brief overview of the AD and sleep literature and then highlight recent advances in the understanding of the relationship between sleep and AD pathogenesis. Importantly, the effects of the bidirectional relationship between the sleep-wake cycle and tau have not been previously discussed in other reviews on this topic. Lastly, we provide possible directions for future studies on the role of sleep in AD.

Neurobehavioural complications of sleep deprivation: Shedding light on the emerging role of neuroactive steroids

Sleep deprivation (SD) is associated with a broad spectrum of cognitive and behavioural complications, including emotional lability and enhanced stress reactivity, as well as deficits in executive functions, decision making and impulse control. These impairments, which have profound negative consequences on the health and productivity of many individuals, reflect alterations of the prefrontal cortex (PFC) and its connectivity with subcortical regions. However, the molecular underpinnings of these alterations remain elusive. Our group and others have begun examining how the neurobehavioural outcomes of SD may be influenced by neuroactive steroids, a family of molecules deeply implicated in sleep regulation and the stress response. These studies have revealed that, similar to other stressors, acute SD leads to increased synthesis of the neurosteroid allopregnanolone in the PFC. Whereas this up-regulation is likely aimed at counterbalancing the detrimental impact of oxidative stress induced by SD, the increase in prefrontal allopregnanolone levels contributes to deficits in sensorimotor gating and impulse control, signalling a functional impairment of PFC. This scenario suggests that the synthesis of neuroactive steroids during acute SD may be enacted as a neuroprotective response in the PFC; however, such compensation may in turn set off neurobehavioural complications by interfering with the corticolimbic connections responsible for executive functions and emotional regulation.

Social and spatial inequalities in allostatic load among adults in China: a multilevel longitudinal study

OBJECTIVES

To investigate potential geographical and socioeconomic patterning of allostatic load (AL) in China.

DESIGN

Multilevel longitudinal study of the 2010 Chronic Disease Risk Factor Surveillance linked to the National Death Surveillance up to 31 December 2015.

SETTING

All 31 provinces in China, not including Hong Kong, Macao or Taiwan.

PARTICIPANTS

96 466 ≥ 18 years old (women=54.3%).

EXPOSURES

Person-level educational attainment and mean years of education in counties.

OUTCOME

AL was measured using clinical guidelines for nine biomarkers: body mass index; waist circumference; systolic blood pressure; diastolic blood pressure; fasting blood glucose; total cholesterol; triglycerides; high-density lipoprotein cholesterol; low-density lipoprotein cholesterol.

RESULTS

Multilevel logistic regressions adjusted for sex, age, marital status, person-level education, county mean years of education and urban/rural reported ORs of 1.22 (95% CI 1.08 to 1.38) for 5-year all-cause mortality (n=3284) and 1.20 (1.04-1.37) for deaths from non-communicable diseases (n=2891) among people in AL quintile 5 (high) compared with quintile 1 (low). The median rate ratio estimated from unadjusted multilevel negative binomial regression showed AL clustered geographically (province=1.14; county=1.12; town=1.11; village=1.14). After adjusting for aforementioned confounders, AL remained higher with age (rate ratio 1.02, 95% CI 1.02 to 1.02), higher in women compared with men (1.17, 1.15 to 1.19), lower among singletons (0.83, 0.81 to 0.85) and widowers (0.96, 0.94 to 0.98). AL was lower among people with university-level compared with no education (0.92, 0.89 to 0.96), but higher in counties with higher mean education years (1.03, 1.01 to 1.05). A two-way interaction suggested AL was higher (1.04, 1.02 to 1.06) among those with university-level compared with no education within counties with higher mean years of education. Similar results were observed for alternative constructions of AL using 75th and 80th percentile cut-points.

CONCLUSIONS

AL in China is patterned geographically. The degree of association between AL and person-level education seems to be dependent on area-level education, which may be a proxy for other contextual factors that warrant investigation.

Decline in telomere length by age and effect modification by gender, allostatic load and comorbidities in National Health and Nutrition Examination Survey (1999-2002)

BACKGROUND

This study aims to assess the decline in telomere length (TL) with age and evaluate effect modification by gender, chronic stress, and comorbidity in a representative sample of the US population.

METHODS

Cross-sectional data on 7826 adults with a TL measurement, were included from the National Health and Nutrition Examination Survey, years 1999-2002. The population rate of decline in TL across 10-year age categories was estimated using crude and adjusted regression.

RESULTS

In an adjusted model, the population rate of decline in TL with age was consistent and linear for only three age categories: 20-29 (β = -0.0172, 95% CI: -0.0342, -0.0002), 50-59 (β = -0.0182, 95% CI: -0.0311, -0.0054) and 70-79 (β = -0.0170, 95% CI: -0.0329, -0.0011) years. The population rate of decline in TL with age was significantly greater for males and those with high allostatic load and a history of comorbidities. When the population rate of decline in TL was analyzed by gender in 10-year age bins, a fairly consistent yet statistically non-significant decline for males was observed; however, a trough in the rate was observed for females in the age categories 20-29 years (β = -0.0284, 95% CI: -0.0464, -0.0103) and 50-59 years (β = -0.0211, 95% CI: -0.0391, -0.0032). To further elucidate the gender difference observed in the primary analyses, secondary analyses were conducted with reproductive and hormonal status; a significant inverse association was found between TL and parity, menopause, and age at menopause.

CONCLUSIONS

TL was shorter with increasing age and this decline was modified by gender, chronic stress and comorbidities; individuals with chronic morbidity and/or chronic stress and females in their twenties and fifties experienced greater decline. Female reproductive factors, i.e., parity and menopause, were associated with TL.

Allostatic Load: Importance, Markers, and Score Determination in Minority and Disparity Populations

Allostatic load is a physiological measure of the cumulative burden of stress on the body assessed by markers of physiological dysregulation. It is a multisystem construct that quantifies biological risk which leads to poor health and maladaptive trajectories. In this overview, which is based on a presentation made at the Flip the Script: Understanding African American Women's Resilience in the Face of Allostatic Load meeting at Ohio State University in August 2018, we build upon previous reviews by discussing four key aspects of allostatic load, specifically its: (1) importance, (2) operationalization, (3) use in minority health and health disparities research, and (4) value in such research. Operationalized in various ways, allostatic load is composed of 10 original markers and additional markers deriving from research among minority and disparity populations. The markers represent four biological systems: (1) cardiovascular, (2) metabolic, (3) inflammatory, and (4) neuroendocrine. System-specific racial/ethnic and sex-based differences have been observed. An overall score can be determined using sample-generated or empirically derived clinically relevant cut points. In summary, allostatic load provides an overall and a body system-specific mechanistic link between exposures to stressors and health outcomes that may help explain health disparities among minority populations.

Direct and indirect associations of cognitive reappraisal and suppression with disease biomarkers

OBJECTIVE

Habitual use of emotion regulation strategies may influence physical health. We examined whether the tendencies to employ cognitive reappraisal and suppression were associated with health biomarkers, and whether stress and sleep quality mediated these associations. Design & main outcome measures: Using data from the Biomarkers substudy (n = 1255) of the national Midlife in the U.S. Study, we tested the hypothesis that there would be indirect, but not direct, associations of cognitive reappraisal and suppression to biomarker indicators of multisystem physiological dysregulation, that is, allostatic load (AL). We computed the proportion of biomarkers in the highest risk quartile within seven biological systems, and summed these scores to compute AL. Associations with the biological systems were also examined separately.

RESULTS

Neither reappraisal nor suppression was directly associated with AL or biomarker function in the seven biological systems. Suppression was indirectly associated with higher AL and greater dysregulation in the inflammatory, metabolic, and hypothalamic-pituitary-adrenal systems via its relations to stress and sleep, p < 0.05. Reappraisal was indirectly associated with lower AL and less metabolic and inflammatory dysregulation, ps<0.05.

CONCLUSIONS

Suppression and reappraisal may have different downstream health effects via stress, sleep, and biomarker expression, suggesting malleable emotion regulation strategies may be an important intervention target.

Exploring the multidimensional complex systems structure of the stress response and its relation to health and sleep outcomes

To gain a comprehensive understanding of the multidimensional complex systems structure of the stress response and related health outcomes, we utilized network analysis in a sample of 328 healthy participants in two steps. In a first step, we focused on associations between measures of basal hypothalamic-pituitary-adrenal axis functioning and subjective stress perceptions. In a second step, we linked these diverse stress-related measures to biomarkers and self-reports of health and sleep. Overall, measures clustered depending on their method of assessment, with high correlations between different saliva-based indices of diurnal cortisol regulation, between cortisol and cortisone levels in hair, between different biological health indicators (systemic inflammatory activity and body mass index), between state (experience sampling) and trait (questionnaire-based) self-reports of stress and wellbeing, and between different self-reports of sleep. Bridges between clusters suggested that if individuals perceive stress throughout their daily lives this is reflected in their total salivary cortisol output possibly contributing to long-term cortisol accumulation in hair. Likewise, earlier awakening time may contribute to cortisol accumulation in hair via an influence on awakening cortisol processes. Our results show that while meaningful connections between measures exist, stress is a highly complex construct composed of numerous aspects. We argue that network analysis is an integrative statistical approach to address the multidimensionality of the stress response and its effects on the brain and body. This may help uncover pathways to stress-related disease and serve to identify starting points for prevention and therapeutic intervention.