Allostatic load may not be associated with chronic stress in pregnant women, NHANES 1999-2006

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.

The Role of Racism in Childhood Obesity

PURPOSE OF REVIEW

Obesity rates continue to rise among children and have shown persistent racial disparities. Racism plays a potentially essential and actionable role in these disparities. This report reviews some mechanisms through which racism may shape childhood obesity.

RECENT FINDINGS

From the youngest ages, disparities in childhood obesity prevalence are already present. Racism may shape intergenerational and prenatal factors that affect obesity and various stressors and environments where children grow up. The relationships between clinicians and patients may also be shaped by everyday racism and legacies of past racism, which may affect obesity prevalence and treatment efficacy. Comprehensive data on the extent to which racism shapes childhood obesity is limited. However, compelling evidence suggests many ways through which racism ultimately does affect childhood obesity. Interventions to address racism at multiple points where it shapes childhood obesity, including intergenerational and prenatal mechanisms, may help to close disparities.

Associations of Socioeconomic Factors and Unhealthy Lifestyles with Allostatic Load: A Meta-analysis

BACKGROUND

Allostatic load (AL) is a biological tool for objectively assessing chronic stress and has been discussed inconsistently for its correlation with socioeconomic factors and unhealthy lifestyles. Therefore, this meta-analysis was performed to explore the impact of socioeconomic factors and unhealthy lifestyles on AL.

METHOD

Different databases, including Web of Science, PubMed, EBSCOhost, Embase, CNKI, VIP, SinoMed, and Wanfang, were searched from inception to June 6, 2023. A total of 25 studies, reporting the correlations of seven socioeconomic factors and three unhealthy lifestyles with AL, were finally included. The pooled odds ratios (OR) and 95% confidence intervals (CIs) were examined using random-effect and fixed-effect models. Literature quality, heterogeneity, and publication bias were evaluated.

RESULTS

The meta-analysis showed a significantly increased risk of high AL in the older individuals as compared to the younger ones (OR = 1.05, 95% CI 1.04-1.06), in the individual with low education as compared to those with high education (OR = 1.25, 95% CI 1.05-1.48), and in the individuals with low physical activities as compared to those with high physical activities (OR = 1.44, 95% CI 1.26-1.64). This meta-analysis also showed a significantly decreased risk of high AL in the individuals with high income as compared to those with low income (OR = 0.77, 95% CI 0.71-0.83) and in women as compared to men (OR = 0.80, 95% CI 0.80-0.81).

CONCLUSION

This meta-analysis showed older people, men, and people having low physical activity, low income, and low education were more likely to have a high AL.

TRIAL REGISTRATION

This meta-analysis was registered on the PROSPERO database with trial registration number CRD42022326105. Instead of providing information at registration, we added an author (Tingyu Mu), who provided critical revisions to the paper in this meta-analysis.

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.

Allostatic Load and Adverse Pregnancy Outcomes

OBJECTIVE

To assess the association between allostatic load, as an estimate of chronic stress, and adverse pregnancy outcomes.

METHODS

This was a secondary analysis of nuMoM2b (Nulliparous Pregnancy Outcomes Study: Monitoring Mothers-to-Be), a prospective observational cohort study. Our primary exposure was dichotomous high allostatic load in the first trimester, defined as 4 or more of 12 biomarkers in the "worst" quartile. The primary outcome was a composite adverse pregnancy outcome: hypertensive disorders of pregnancy (HDP), preterm birth, small for gestational age (SGA), and stillbirth. Secondary outcomes included components of the composite. Multivariable logistic regression was used to test the association between high allostatic load and adverse pregnancy outcomes, adjusted for potential confounders. Mediation and moderation analyses were conducted to assess the role of allostatic load along the causal pathway between racial disparities and adverse pregnancy outcomes.

RESULTS

Among 4,266 individuals, 34.7% had a high allostatic load. Composite adverse pregnancy outcome occurred in 1,171 (27.5%): 14.0% HDP, 8.6% preterm birth (48.0% spontaneous and 52.2% indicated), 11.0% SGA, and 0.3% stillbirth. After adjustment for maternal age, gravidity, smoking, bleeding in the first trimester, and health insurance, high allostatic load was significantly associated with a composite adverse pregnancy outcome (adjusted odds ratio [aOR] 1.5, 95% CI 1.3, 1.7) and HDP (aOR 2.5, 95% CI 2.0-2.9), but not preterm birth or SGA. High allostatic load partially mediated the association between self-reported race and adverse pregnancy outcomes. The association between allostatic load and HDP differed by self-reported race, but not for a composite adverse pregnancy outcome, preterm birth, or SGA.

CONCLUSION

High allostatic load in the first trimester is associated with adverse pregnancy outcomes, particularly HDP. Allostatic load was a partial mediator between race and adverse pregnancy outcomes. The association between allostatic load and HDP differed by self-reported race.

Prenatal allostatic load and preterm birth: A systematic review

Objective

Allostatic load refers to cumulative neuroendocrine burden and has been postulated to mediate and moderate physiological and psychological stress-related responses. This may have important implications for the risk of preterm birth. This systematic review examines the evidence on the association between prenatal allostatic load and preterm birth.

Data sources

A comprehensive search of seven electronic databases was conducted from inception to August 23, 2022 to identify all English-language observational and mixed methods studies examining allostatic load and preterm birth with no year or geographic restrictions.

Study eligibility criteria

Studies were included if they measured allostatic load, evaluated as the cumulative effect of any combination of more than one allostatic load biomarker, during pregnancy. Studies must have observed preterm birth, defined as < 37 weeks' gestational age, as a primary or secondary outcome of interest.

Study appraisal and synthesis methods

The Quality In Prognosis Studies tool was used to evaluate risk of bias within included studies. A narrative synthesis was conducted to explore potential associations between allostatic load and preterm birth, and sources of heterogeneity.

Results

Three prospective cohort studies were identified and revealed mixed evidence for an association between allostatic load and preterm birth. One study reported a statistically significant association while the other two studies reported little to no evidence for an association. Heterogeneity in when and how allostatic load was measured, limitations in study design and cohort socio-demographics may have contributed to the mixed evidence.

Conclusions

This review provides insight into key individual-, community-, and study-level characteristics that may influence the association between allostatic load and preterm birth. Knowledge gaps are identified as foci for future research, including heterogeneity in allostatic load biomarkers and allostatic load index algorithms as well as pregnancy-specific considerations for allostatic load measurement. Further investigation of the allostatic load framework in the context of perinatal mental health is needed to advance understandings of maternal, infant, and child health.

Systematic review registration

https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42020208990, PROSPERO, identifier: CRD42020208990.

Breastfeeding Is Inversely Associated with Allostatic Load in Postpartum Women: Cross-Sectional Data from Nationally Representative US Women

BACKGROUND

The postpartum period is a critical transition period when exposures to protective factors such as breastfeeding can have long-lasting health impact. Studies have suggested downregulating effects of breastfeeding on stress biomarkers such as cortisol but have not explored the way breastfeeding interacts with allostatic load, a multisystem indicator of chronic stress.

OBJECTIVE

We aimed to examine the association between breastfeeding and maternal allostatic load among women within 2 y postpartum using nationally representative data.

METHODS

A cross-sectional analysis of 10 waves of data from the NHANES (1999-2018) was conducted in a sample of 1302 women aged ≥18 y who provided information on breastfeeding through the reproductive health questionnaire. Clinical and empirical allostatic load scores (range: 0-10; higher numbers associated with increased risk) were derived for each participant based on 10 biomarkers reflecting metabolic, cardiovascular, and immune health. Multiple linear regression tested associations between breastfeeding and allostatic load, adjusting for maternal age, race and ethnicity, education, poverty level, and survey wave.

RESULTS

Breastfeeding had a significant inverse association with allostatic load in unadjusted and adjusted models. Controlling for age, race and ethnicity, education, poverty level, and survey wave, breastfeeding women had a 0.36-point lower clinical allostatic load score than nonbreastfeeding women (β = -0.36, SE = 0.11; 95% CI: -0.59, -0.14; P = 0.002) and a 0.44-point lower empirical allostatic load score (β = -0.44, SE = 0.15; 95% CI: -0.74, -0.14; P = 0.005).

CONCLUSIONS

Our study suggests that breastfeeding is protective of maternal stress and provides a more comprehensive picture of breastfeeding's influence on multiple body systems, exemplifying physiological benefits beyond effects on single biomarkers. However, limitations of cross-sectional data and non-classification of breastfeeding duration, mode, and intensity should be considered when interpreting these findings, and further research to address the role of breastfeeding and allostatic load is needed.

Allostatic Load and Its Impact on Health: A Systematic Review

INTRODUCTION

Allostatic load refers to the cumulative burden of chronic stress and life events. It involves the interaction of different physiological systems at varying degrees of activity. When environmental challenges exceed the individual ability to cope, then allostatic overload ensues. Allostatic load is identified by the use of biomarkers and clinical criteria.

OBJECTIVE

To summarize the current knowledge on allostatic load and overload and its clinical implications based on a systematic review of the literature.

METHODS

PubMed, PsycINFO, Web of Science, and the Cochrane Library were searched from inception to December 2019. A manual search of the literature was also performed, and reference lists of the retrieved articles were examined.We considered only studies in which allostatic load or overload were adequately described and assessed in either clinical or non-clinical adult populations.

RESULTS

A total of 267 original investigations were included. They encompassed general population studies, as well as clinical studies on consequences of allostatic load/overload on both physical and mental health across a variety of settings.

CONCLUSIONS

The findings indicate that allostatic load and overload are associated with poorer health outcomes. Assessment of allostatic load provides support to the understanding of psychosocial determinants of health and lifestyle medicine. An integrated approach that includes both biological markers and clinimetric criteria is recommended.

Allostatic Load Among Black Sexual Minority Women

Background: Allostatic load is the physiological deterioration that accumulates as the body responds to stress, resulting in disparities in chronic disease. Although perceptions of stress vary, marginalization and social disadvantage are associated with elevated allostatic load. Allostatic load is understudied in the multiply marginalized populations of sexual minority Black women. Methods: We used data from six waves of the National Health and Nutrition Examination Survey (2001-2010, 2015-2016) to identify heterosexual (n = 78), lesbian (n = 21), and bisexual (n = 57) Black women. We quantified allostatic load using nine biomarkers, and compared mean allostatic load across the three groups, adjusting for age, educational attainment, income, and country of birth to account for possible confounding. Results: We found no significant differences in allostatic load among heterosexual, lesbian, and bisexual Black women. Conclusions: These findings suggest that sexual orientation may not contribute to within-group differences in allostatic load among Black women, a group previously noted to have elevated allostatic load.

Allostatic load and mental health: a latent class analysis of physiological dysregulation

This study explored the associations between specific profiles of biological dysregulation and mental health outcomes in a national, community sample of healthy adults in the United States. A latent class analysis of data from the Midlife Development in the United States study (n = 1,757) was conducted to determine classes of biological dysregulation. Multinomial logistic regressions of class membership were employed to determine associations with measures related to depression, including whether or not individuals had sought treatment, Center for Epidemiological Studies Depression Scale, and both the generalized distress and anhedonia subscales of the Mood and Anxiety Symptoms Questionnaire. Four classes of dysregulation emerged: baseline/low dysregulation, metabolic and inflammatory dysregulation, parasympathetic dysregulation, and SAM pathway dysregulation. Individuals who met the criteria for depression measures were more likely to be in the metabolic and immune dysregulation and parasympathetic dysregulation groups as compared to the baseline group. The results suggest that mental health outcomes, such as depression, are differentially associated with specific profiles of biological dysregulation. A more nuanced approach to profiles of dysregulation could better inform treatment decisions.Lay summaryHigher levels of allostatic load, which represents the cumulative wear and tear of exposure to stress, are associated with increased rates of depression and anhedonia. Specifically, parasympathetic dysregulation and immunometabolic dysregulation are associated with negative mental health outcomes.

Allostatic load: Developmental and conceptual considerations in a multi-system physiological indicator of chronic stress exposure

Developmental researchers studying how stress affects health have often focused on specific, individual, physiological parameters such as cortisol. Yet, recent theories of stress biology emphasize that the stress response is multi-faceted and engages distinct yet interconnected physiological systems, including metabolic, immune, and cardiovascular systems that respond to one another. Moreover, advocates of a systems approach also argue that the confluence of changes across several physiological systems presents a health risk, even when one indicator alone is not predictive of health outcomes. Allostatic load is one potential multi-system indicator of stress, capturing the cumulative, physiological burden of chronic stress exposure on the body. At the same time, studying allostatic load during early development raises several issues, including how allostatic load is operationalized, the clinical importance of commonly used biomarkers during distinct periods of development, and the fundamental role of timing. In this review paper, we discuss the potential of allostatic load in the context of studies of stress in developmental science, review developmental studies that have assessed allostatic load, and articulate critical conceptual questions regarding the study of allostatic load during the childhood years.

Antepartum Depression and Preterm Birth: Pathophysiology, Epidemiology, and Disparities due to structural racism

PURPOSE OF REVIEW

Informed by the evidence of links between physiology of stress and parturition, we review recent epidemiologic evidence (2015-2020) of antenatal depression as a risk factor for preterm birth (PTB). We also explain racial/ethnic disparities in depression and preterm birth as a consequence of structural racism.

RECENT FINDINGS

Epidemiologic evidence is consistent in linking antepartum depression with an elevated risk of PTB. Antidepressant usage has been linked with an elevated risk of PTB. However, recent evidence suggests that severity of depression is the underlying driver of the elevated risk attributed to antidepressant usage. The number of depressive symptoms, as a proxy for severity of maternal stress, may be a more informative predictor of PTB than criterion based predictors. Across various study designs, measurement modalities, and populations, antenatal depression predicts an elevated risk of delivering preterm. The physiology of stress provides a plausible explanation for this observation. Excessive stress-induced elevations in maternal and then fetal HPA hormones can alter maternal and fetal homeostasis and hasten the timing of parturition. Antenatal depression and exposure to structural racism are two stressors that can trigger the maternal stress response. Chronically elevated levels of stress hormones among women of color in the USA provide a likely physiologic explanation for Black-White disparities in the risk of PTB. Focusing on the number of depressive symptoms as the more informative predictor of PTB raises several questions. We consider these questions as well as directions for future research in the context of recent advances in the field.

Acknowledging and Addressing Allostatic Load in Pregnancy Care

The USA is one of the few countries in the world in which maternal and infant morbidity and mortality continue to increase, with the greatest disparities observed among non-Hispanic Black women and their infants. Traditional explanations for disparate outcomes, such as personal health behaviors, socioeconomic status, health literacy, and access to healthcare, do not sufficiently explain why non-Hispanic Black women continue to die at three to four times the rate of White women during pregnancy, childbirth, or postpartum. One theory gaining prominence to explain the magnitude of this disparity is allostatic load or the cumulative physiological effects of stress over the life course. People of color disproportionally experience social, structural, and environmental stressors that are frequently the product of historic and present-day racism. In this essay, we present the growing body of evidence implicating the role of elevated allostatic load in adverse pregnancy outcomes among women of color. We argue that there is a moral imperative to assign additional resources to reduce the effects of elevated allostatic load before, during, and after pregnancy to improve the health of women and their children.

Concomitant exposure to area-level poverty, ambient air volatile organic compounds, and cardiometabolic dysfunction: a cross-sectional study of U.S. adolescents

PURPOSE

A key to better understanding the influence of the place of residence on cardiometabolic function is the effect of concomitant exposure to both air pollution and residence in economically marginalized areas. We hypothesized that, among adolescents, the association between air pollution and cardiometabolic function is exacerbated among residents of economically marginalized areas.

METHODS

In this cross-sectional study, individual-level data on cardiometabolic function collected from a representative sample of U.S. adolescents in the National Health and Nutrition Examination Survey (n = 10,415) were merged with data on area-level poverty (U.S. decennial survey and American Community Survey) and air pollution levels (National-Scale Air Toxics Assessment ) using contemporary census-tract identifiers. We excluded respondents who were pregnant, had hypertension or diabetes or using medication for hypertension or diabetes, or with missing data on outcome variables.

RESULTS

We observed a significant interaction between area-level poverty and air pollution. Among residents of high-poverty areas, exposure to high levels of air pollution predicted a 30% elevated odds of cardiometabolic dysfunction (OR = 1.30; 95% CI: 1.04, 1.61), whereas in low-poverty areas, exposure to high levels of air pollution was not associated with elevated odds of cardiometabolic dysfunction (OR = 1.04; 95% CI: 0.85, 1.28).

CONCLUSIONS

Our findings suggest that the cardiometabolic consequences of air pollution are more readily realized among residents of economically marginalized areas. Structural remedies are discussed.

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.

Allostatic load, a measure of chronic physiological stress, is associated with pregnancy outcomes, but not fertility, among women with unexplained infertility

STUDY QUESTION

Among infertile women undergoing ovarian stimulation, is allostatic load (AL), a measure of chronic physiological stress, associated with subsequent fertility and pregnancy outcomes?

SUMMARY ANSWER

AL at baseline was not associated with conception, spontaneous abortion or live birth, however, it was significantly associated with increased odds of pre-eclampsia and preterm birth among women who had a live birth in the study.

WHAT IS KNOWN ALREADY

Several studies have linked AL during pregnancy to adverse outcomes including preterm birth and pre-eclampsia, hypothesizing that it may contribute to well-documented disparities in pregnancy and birth outcomes. However, AL biomarkers change over the course of pregnancy, raising questions as to whether gestational AL assessment is a valid measure of cumulative physiologic stress starting long before pregnancy. To better understand how AL may impact reproductive outcomes, AL measurement in the non-pregnant state (i.e. prior to conception) is needed.

STUDY DESIGN, SIZE, DURATION

A secondary data analysis based on data from 836 women who participated in Assessment of Multiple Intrauterine Gestations from Ovarian Stimulation (AMIGOS), a multi-center, randomized clinical trial of ovarian stimulation conducted from 2011 to 2014.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Ovulatory women with unexplained infertility (ages 18-40) were enrolled and at baseline, biological and anthropometric measures were collected. AL scores were calculated as a composite of the following baseline variables determined a priori: BMI, waist-to-hip ratio, systolic blood pressure, diastolic blood pressure, dehydroepiandrosterone sulfate, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, triglycerides, C-reactive protein and HOMA score. Participants received ovarian stimulation for up to four cycles and if they conceived, were followed throughout pregnancy. We fit multi-variable logistic regression models examining AL (one-tailed and two-tailed) in relation to the following reproductive outcomes: conception, spontaneous abortion, live birth, pre-eclampsia, preterm birth and low birthweight.

MAIN RESULTS AND THE ROLE OF CHANCE

Adjusting for covariates, a unit increase in two-tailed AL score was associated with 62% increased odds of pre-eclampsia (OR: 1.62, 95% CI: 1.14, 2.38) 44% increased odds of preterm birth (OR: 1.44, 95% CI: 1.02, 2.08), and 39% increased odds of low birthweight (OR: 1.39, 95% CI: 0.99, 1.97). The relationship between AL and preterm birth was mediated by pre-eclampsia (P = 0.0003). In one-tailed AL analyses, associations were similar, but slightly attenuated. AL was not associated with fertility outcomes (conception, spontaneous abortion, live birth).

LIMITATIONS, REASONS FOR CAUTION

Results may not be generalizable to fertile women who conceive naturally or women with other types of infertility. Comparisons to previous, related work are difficult because variables included in AL composite measures vary across studies. AL may be indicative of overall poor health, rather than being specific to chronic physiological stress.

WIDER IMPLICATIONS OF THE FINDINGS

Our results suggest that chronic physiological stress may not impact success of ovarian stimulation, however, they confirm and extend previous work suggesting that AL is associated with adverse pregnancy outcomes. Physiological dysregulation due to chronic stress has been proposed as a possible mechanism underlying disparities in birth outcomes, which are currently poorly understood. Assessing biomarkers of physiological dysregulation pre-conception or in early pregnancy, may help to identify women at risk of adverse pregnancy outcomes, particularly pre-eclampsia.

STUDY FUNDING/COMPETING INTEREST(S)

Support for AMIGOS was provided by: U10 HD39005, U10 HD38992, U10 HD27049, U10 HD38998, U10 HD055942, HD055944, U10 HD055936 and U10HD055925. Support for the current analysis was provided by T32ES007271, R25HD075737, P30ES001247 and P30ES005022. This research was made possible by funding by American Recovery and Reinvestment Act. The content is solely the responsibility of the authors and does not necessarily represent the official views of NICHD, NIEHS or NIH. E.B., W.V., O.M., R.A., M.R., V.B., G.W.B., C.C., E.E., S.K., R.U., P.C, H.Z., N.S. and S.T. have nothing to disclose. R.L. reported serving as a consultant to Abbvie, Bayer, Kindex, Odega, Millendo and Fractyl and serving as a site investigator and receiving grants from Ferring. K.H. reported receiving grants from Roche Diagnostics and Ferring. R.R. reported a grant from AbbVie. M.D. reported being on the Board of Directors of and a stockholder in Advanced Reproductive Care.

TRIAL REGISTRATION NUMBER

Clinical Trials.gov number: NCT01044862.

Giving a good start to a new life via maternal brain allostatic adaptations in pregnancy

Successful pregnancy requires adjustments to multiple maternal homeostatic mechanisms, governed by the maternal brain to support and enable survival of the growing fetus and placenta. Such adjustments fit the concept of allostasis (stability through change) and have a cost: allostatic load. Allostasis is driven by ovarian, anterior pituitary, placental and feto-placental hormones acting on the maternal brain to promote adaptations that support the pregnancy and protect the fetus. Many women carry an existing allostatic load into pregnancy, from socio-economic circumstances, poor mental health and in 'developed' countries, also from obesity. These pregnancies have poorer outcomes indicating negative interactions (failing allostasis) between pre-pregnancy and pregnancy allostatic loads. Use of animal models, such as adult prenatally stressed female offspring with abnormal neuroendocrine, metabolic and behavioural phenotypes, to probe gene expression changes, and epigenetic mechanisms in the maternal brain in adverse pregnancies are discussed, with the prospect of ameliorating poor pregnancy outcomes.

Innovations in biological assessments of chronic stress through hair and nail cortisol: Conceptual, developmental, and methodological issues

Much of the existing research on biological mechanisms underlying the stress experience has focused largely on moment-to-moment stress, rather than on chronic stress, an arguably more powerful predictor of long-term outcomes. Recent methodological innovations have paved the way for new lines of research on chronic stress, with promising implications for developmental researchers and for those who study health and adversity. In particular, there are increasing studies that have focused on chronic stress assessments by relying on cortisol derived from hair and nails as a biomarker for chronic stress. In this paper, we provide an overview of their use, describe how hair and nail cortisol ought to be conceptualized differently across the lifespan, how developmental factors may impact its interpretation, and the circumstances under which its use may be more methodologically sensible. The purpose of this review is to provoke further discussion and encourage careful research designs that utilize hair and nail cortisol for understanding the effects of chronic stress exposure from the early developmental period, across adverse contexts, and in association with psychological and physical health outcomes.

Cumulative Physiologic Dysfunction and Pregnancy: Characterization and Association with Birth Outcomes

Objective To characterize cumulative physiologic dysfunction (CPD) in pregnancy as a measure of the biological effects of chronic stress and to examine its associations with gestational age and birth weight. Methods Women ≤28 weeks gestation were enrolled from obstetric clinics in Rochester, NY and followed through their delivery. CPD parameters included total cholesterol, Interleukin 6 (IL-6), high sensitivity-C-reactive protein (hs-CRP), systolic and diastolic blood pressure, body mass index at <14 weeks gestation, glucose tolerance, and urinary albumin collected in the third trimester. Linear regression was used to estimate the association between physiologic dysfunction and birth weight and gestational age, respectively (N = 111). Results CPD scores ranged from 0 to 6, out of a total of 8 parameters (Mean 2.09; SD = 1.42). Three-fourths of the participants had a CPD score of 3.0 or lower. The mean birth weight was 3397 g (SD = 522.89), and the mean gestational age was 39.64 weeks (SD = 1.08). CPD was not significantly associated with either birth weight or gestational age (p = 0.42 and p = 0.44, respectively). Conclusion CPD measured at >28 weeks was not associated with birth weight or gestational age. Refinement of a CPD score for pregnancy is needed, taking into consideration both the component parameters and clinical and pre-clinical cut-points for risk scoring.

The contribution of three dimensions of allostatic load to racial/ethnic disparities in poor/fair self-rated health

Objective

This study evaluates whether different dimensions of physiological dysregulation, modeled individually rather than additively mediate racial/ethnic disparities in self-reported health.

Methods

Using data from the National Health and Nutrition Examination Survey (2005–2010) and the Karlson, Hold, and Breen (KHB) mediation model, this paper explores what operationalization of biomarker data most strongly mediate racial/ethnic disparities in poor/fair self-rated health (SRH) among adults in the United States, net of demographic, socioeconomic, behavioral, and medication controls.

Results

Non-Hispanic blacks and Hispanics had significantly higher odds of reporting poor/fair self-rated health in comparison to non-Hispanic whites. Operationalizations of allostatic load that disaggregate three major dimensions of physiological dysregulation mediate racial/ethnic disparities strongly between non-Hispanic blacks and non-Hispanic whites, but not between Hispanics and non-Hispanic whites. Disaggregating these dimensions explains racial/ethnic disparities in poor/fair SRH better than the continuous score. Analyses on sex-specific disparities indicate differences in how individual dimensions of allostatic load contribute to racial/ethnic disparities in poor/fair SRH differently. All individual dimensions are strong determinants of poor/fair SRH for males. In contrast, for females, the only dimension that is significantly associated with poor/fair SRH is inflammation. For the analytic sample, additive biomarker scores fit the data as well or better than other approaches, suggesting that this approach is most appropriate for explaining individual differences. However, in sex-specific analyses, the interactive approach models fit the data best for men and women.

Conclusions

Future researchers seeking to explain racial/ethnic disparities in full or sex-stratified samples should consider disaggregating allostatic load by dimension.

•

Non-Hispanic blacks and Hispanics have higher rates of poor/fair self-rated health and levels of allostatic load

•

Allostatic load mediates the race/ethnicity-self rated health relationship.

•

Overall, dividing allostatic load into three dimensions better explains the white-black gap

•

In sex-specific models interactive approaches better explain self-rated health

Allostatic load in early pregnancy is associated with poor sleep quality

BACKGROUND

Allostatic load (AL) measures the cumulative impact of chronic stress and is associated with adverse health outcomes. A novel scoring system has previously been developed for AL in early pregnancy that is associated with pre-eclampsia. It was hypothesized that AL, as identified by the present model, is associated with psychosocial stressors and, specifically, poor sleep quality.

METHODS

Women were selected from a low-risk, community-dwelling study population who enrolled at <15 weeks gestation. Nine physiologic components were divided among the domains of cardiovascular, metabolic, and inflammatory function. Spearman's rank correlations were used to examine the association of AL with age, income, the Revised Prenatal Distress Questionnaire (NuPDQ), Inventory of Depressive Symptoms (IDS), and Pittsburgh Sleep Quality Index (PSQI). The Wilcoxon rank-sum test was used to compare AL by race and educational attainment.

RESULTS

A total of 103 women were identified, with: a mean age of 29.8 ± 5.0 years, 17.5% black, and mean gestational age 12.2 ± 1.1 weeks. Allostatic load was positively correlated with the PSQI (ρ = 0.23, p = 0.018). There were no associations with age, income, prenatal distress, race, or depression scores. College-educated women had lower AL compared with those with less education (0.57 ± 0.43 vs 0.81 ± 0.55, p = 0.045).

CONCLUSION

Higher AL, measured by the pregnancy-specific model, was associated with poorer sleep quality and lower educational attainment, both of which were considered to be chronic stressors. These relationships were consistent with previous findings in non-pregnant populations, and suggest that AL may be useful for capturing the physiologic impact of chronic stress in early pregnancy.

Allostatic load: a useful concept for advancing nursing research

AIMS AND OBJECTIVES

To elucidate the historical development of the allostatic load concept, alongside its use in nursing research, and to explore how allostatic load has been investigated among two stress-vulnerable populations.

BACKGROUND

'Stress' is a prominent term in understanding the development of disease. Allostatic load is among several approaches undertaken to quantify the magnitude of stress and understand how stress can affect health.

METHOD

We explored the advent of allostatic load including its antecedents, and consequences. We used an exemplar case to apply the concept. We reviewed studies that used allostatic load among workers and women of childbearing age.

RESULTS

There remains a need to consolidate a common definition and operationalisation of allostatic load. Despite this need for further work, allostatic load is a good fit for nursing science which focuses on the client, environment and health. Only 12 studies explored allostatic load among workers (n = 6) and women of childbearing age (n = 6). In some studies, allostatic load was used as a predictor while in others it was used as an outcome. None of the studies considered it as a mediator.

CONCLUSIONS

The concept of allostatic load holds promise for nursing researchers to operationalise a holistic view of multiple stressors and to quantify their effects on health. Studies are needed to affirm the role of allostatic load as a potential mediator between multiple stressors and outcomes. Longitudinal studies are also needed to demonstrate a causal pathway from stressor exposure to tertiary outcomes such as chronic conditions and morbidity.

RELEVANCE TO CLINICAL PRACTICE

Allostatic load is a useful concept for nurses working with stress-vulnerable populations. With the use of an interpretable allostatic load index, nurses will be able to intervene at various stages of the allostasis-adaptation process (stress-response) and adjust interventions accordingly.

Explaining racial and ethnic inequalities in postpartum allostatic load: Results from a multisite study of low to middle income woment

BACKGROUND

Racial and ethnic inequalities in women's health are widely documented, but not for the postpartum period, and few studies examine whether neighborhood, psychosocial, and biological factors explain these gaps in women's health.

METHODS

Using prospective longitudinal data collected from 1766 low to middle income women between 2008 and 2012 by the Community Child Health Network (CCHN), we tested the extent to which adjustment for neighborhood, economic, psychological, and medical conditions following a birth explained differences between African American, Latina, and White women in an indicator of physiological dysregulation allostatic load (AL), at one year postpartum as measured by 10 biomarkers: Body Mass Index, Waist Hip Ratio, systolic and diastolic blood pressure, high sensitivity C-reactive protein, Hemoglobin A1c, high-density lipoprotein and cholesterol ratio, and diurnal cortisol.

RESULTS

Mean postpartum AL scores were 4.65 for African American, 4.57 for Latina and 3.86 for White women. Unadjusted regression estimates for high AL for African American women (with White as the reference) were 0.80 (SD = 0.11) and 0.53 (SD = 0.15) for Latina women. Adjustment for household poverty, neighborhood, stress, and resilience variables resulted in a reduction of 36% of the excess risk in high AL for African Americans versus Whites and 42% of the excess risk for Latinas compared to Whites.

CONCLUSIONS

Racial and ethnic inequalities in AL were accounted for largely by household poverty with additional contributions by psychological, economic, neighbourhood and medical variables. There remained a significant inequality between African American, and Latina women as compared to Whites even after adjustment for this set of variables. Future research into health inequalities among women should include a fuller consideration of the social determinants of health including employment, housing and prepregnancy medical conditions.

Relationship Between Mean Leucocyte Telomere Length and Measures of Allostatic Load in US Reproductive-Aged Women, NHANES 1999-2002

BACKGROUND

Reproductive health disparities may be partly explained by the cumulative effects of chronic stress experienced by socially disadvantaged groups. Although, telomere length (TL) and allostatic load score have each been used as biological markers of stress, the relationship between these two measures is unknown.

METHODS

We investigated the association between leucocyte TL and allostatic load score in 1503 non-pregnant women (20-44 years) participating in the National Health and Nutrition Examination Survey, 1999-2002. We constructed six different allostatic load scores using either quartile- or clinical-based cut-points for 14 biomarkers based on previously published methods. We estimated associations between TL and allostatic load scores and component biomarkers using linear regression, also assessing interactions by race/ethnicity.

RESULTS

After adjustment for age, longer TL was associated with higher HDL cholesterol and lower C-reactive protein and creatinine clearance; TL was not associated with the other component biomarkers. Shorter TL was associated with higher allostatic load scores for the two clinical cut-point-based scores after adjustment for age, but not the four scores based on quartile cut-points. Significant interactions by race/ethnicity were observed for TL and HbA1c and triglycerides, but not for other component biomarkers or allostatic load scores.

CONCLUSIONS

Although TL and allostatic load score are both considered measures of cumulative stress, most component biomarkers and scores using quartile-based cut-points were not associated with TL. In reproductive-aged women, allostatic load scores using clinical-based cut-points were more strongly associated with TL compared with quartile-based scores.

A potential role for allostatic load in preeclampsia

Preeclampsia is a multisystemic disorder of pregnancy associated with maternal and fetal complications as well as later-life cardiovascular disease. Its exact cause is not known. We developed a pregnancy-specific multisystem index score of physiologic risk and chronic stress, allostatic load (AL), early in pregnancy. Our objective was to determine whether AL measured early in pregnancy was associated with increased odds of developing preeclampsia. Data were from a single-center, prospectively collected database in a 1:2 individual-matched case control of women enrolled at <15 weeks gestation. We matched 38 preeclamptic cases to 75 uncomplicated, term deliveries on age, parity, and lifetime smoking status. AL was determined using 9 measures of cardiovascular, metabolic, and inflammatory function. Cases and matched controls were compared using conditional logistic regression. We compared the model's association with preeclampsia to that of obesity, a well-known risk factor for preeclampsia, by assessing goodness-of-fit by Akaike information criterion (AIC), where a difference >1-2 suggests better fit. Early pregnancy AL was higher in women with preeclampsia (1.25 ± 0.68 vs. 0.83 ± 0.62, p = 0.002); women with higher AL had increasing odds of developing preeclampsia (OR 2.91, 95 % CI 1.50-5.65). The difference between AIC for AL and obesity was >2 (AIC 74.4 vs. 84.4), indicating AL had a stronger association with preeclampsia. Higher allostatic load in early pregnancy is associated with increasing odds of preeclampsia. This work supports a possible role of multiple maternal systems and chronic stress early in pregnancy in the development of preeclampsia.

Maternal and pediatric health and disease: integrating biopsychosocial models and epigenetics

The concepts of allostasis (stability through adaptation) and accumulated life stress (McEwen's allostatic load) aim to understand childhood and adult outcomes. Chronic malnutrition, changes in social condition, and adverse early-life experiences may program phenotypes and contribute to long-lasting disease risk. However, integration of life course approaches, social and economic contexts, and comparison among different biopsychosocial models has not generally been explored. This review critically examines the literature and evaluates recent insights into how environmental stress can alter lifelong hypothalamic-pituitary-adrenal axis and immune system responsiveness and induce metabolic and neurodevelopmental maladaptation. Models of biopsychosocial stress overlap but may consider different conditions. Concepts include allostasis, which incorporates hormonal responses to predictable environmental changes, and Geronimus's "weathering," which aims to explain how socially structured, repeated stress can accumulate and increase disease vulnerability. Weathering emphasizes roles of internalized/interpersonal racism in outcomes disparities. For Mexican immigrants and Mexican Americans, the "acculturation" framework has proven especially useful to explore disparities, including preterm birth and neuropsychiatric risks in childhood. Complexities of stress assessments and recent research into epigenetic mechanisms mediating effects of physical, nutritional, psychological, and social stress are reviewed.

Allostatic Load and Preterm Birth

Preterm birth is a universal health problem that is one of the largest unmet medical needs contributing to the global burden of disease. Adding to its complexity is that there are no means to predict who is at risk when pregnancy begins or when women will actually deliver. Until these problems are addressed, there will be no interventions to reduce the risk because those who should be treated will not be known. Considerable evidence now exists that chronic life, generational or accumulated stress is a risk factor for preterm delivery in animal models and in women. This wear and tear on the body and mind is called allostatic load. This review explores the evidence that chronic stress contributes to preterm birth and other adverse pregnancy outcomes in animal and human studies. It explores how allostatic load can be used to, firstly, model stress and preterm birth in animal models and, secondly, how it can be used to develop a predictive model to assess relative risk among women in early pregnancy. Once care providers know who is in the highest risk group, interventions can be developed and applied to mitigate their risk.

Allostatic load in women with a history of low birth weight infants: the national health and nutrition examination survey

BACKGROUND

The purpose of our study was to determine whether women of reproductive age with history of low birth weight (LBW) deliveries have higher allostatic load (AL), a measure of the cumulative toll of chronic stress, than those with normal-weight deliveries.

METHODS

We used data from women ages 17-35 who responded to the National Health and Nutrition Examination Survey (NHANES) reproductive-health questionnaire, 1999-2006. Women reported history of LBW infants and those who were preterm. We classified preterm-LBW and term-LBW as surrogates for preterm birth (PTB) and small for gestational age (SGA), respectively. Normal weight included those without LBW infant history. We utilized nine biomarkers measured in NHANES to determine AL and used linear regression to compare unadjusted and adjusted means.

RESULTS

We identified 877 women divided among SGA (2%), PTB (10%), and normal groups (88%). The SGA group had higher unadjusted and adjusted AL scores than did the normal group (2.82 ± 0.35 vs. 1.92 ± 0.07, p=0.011); women in the PTB group had higher AL scores than did the referent in adjusted analyses (2.58 ± 0.21 vs. 1.92 ± 0.07, p=0.001).

CONCLUSIONS

Women with history of SGA or PTB had higher AL than did those with normal birth weight outcomes. This suggests a link between adverse pregnancy outcomes, chronic stress, and subclinical disease.

Life course approach in social epidemiology: an overview, application and future implications

The application of the life course approach to social epidemiology has helped epidemiologists theoretically examine social gradients in population health. Longitudinal data with rich contextual information collected repeatedly and advanced statistical approaches have made this challenging task easier. This review paper provides an overview of the life course approach in epidemiology, its research application, and future challenges. In summary, a systematic approach to methods, including theoretically guided measurement of socioeconomic position, would assist researchers in gathering evidence for reducing social gradients in health, and collaboration across individual disciplines will make this task achievable.

Joint exposure to chemical and nonchemical neurodevelopmental stressors in U.S. women of reproductive age in NHANES

Lead (Pb) and methyl mercury (MeHg) are well established neurodevelopmental toxicants (NDTs), but joint exposure to chemical and nonchemical (e.g., maternal stress) stressors has rarely been considered. We characterized exposure to Pb, MeHg and a measure of physiological dysregulation associated with chronic stress and examined race/ethnicity as a predictor of joint NDT exposure. Using data from the 2003-2004 NHANES, potential chronic stress exposure was estimated using allostatic load (AL), a quantitative measure of physiological dysregulation. A Hazard Index was calculated for joint exposure to Pb and MeHg (HI(NDT)). Logistic regression was used to assess the relationship between an indicator of elevated joint NDT exposures (HI(NDT) > 1) and race/ethnicity. The multivariate model was stratified by AL groups to examine effect measure modification. African American (adjusted odds ratio [OR] [95% confidence interval] = 2.2 [1.4, 3.3]) and Mexican American (1.4 [0.7, 2.6]) women were more likely to have an HI(NDT) > 1 compared to Caucasian women. Chronic stress was identified as an effect measure modifier with the largest ORs among women with high AL scores (African Americans = 4.3 [2.0, 9.5]; Mexican Americans = 4.2 [1.3, 14.1]). Chronic stress was found to modify the association between elevated joint NDT exposure and race/ethnicity, highlighting the importance of evaluating chemical and nonchemical stressor exposures leading to a common endpoint.