Association of allostatic load with brain structure and cognitive ability in later life

Allostatic load, a measure of cumulative physiological stress, impairs brain structure but not β-accumulation in older adults: an exploratory study

Introduction

Allostatic load (AL) is a composite score of progressive physiological dysregulations in response to long-term exposure to everyday stress. Despite growing interest, limited research has focused on links with cerebral and cognitive aspects of aging and with markers sensitive to Alzheimer's disease (AD) in a healthy elderly population and with a multimodal approach.

Methods

At baseline, 111 older adults (without cognitive impairment) from the Age-Well trial completed blood and anthropometric markers collection, cognitive assessments and multimodal neuroimaging within 3 months.

Results

AL was negatively associated with gray matter volume and white matter integrity within frontal and temporal regions and poorer attentional performance.

Discussion

AL is linked to structural brain integrity in aging- and stress-sensitive regions but not with AD-related markers (β-amyloid load) and only in two AD-sensitive brain regions in older adults. These results highlight the potential interest of AL as a sensitive index of stress-induced brain aging.

Measuring the Interrelationships Between Cognitive Performance, Race/Ethnicity, Discrimination, Health Behaviors, and Physiological Dysregulation: A Path Analysis of the Multi-Ethnic Study of Atherosclerosis

ObjectiveThe objective of this study was to examine the interrelationships between cognitive performance, race/ethnicity, discrimination, health behaviors, and physiological dysregulation.MethodsWe used data from the Multi-Ethnic Study of Atherosclerosis (MESA) (N = 1667). We used path analyses to examine the association between discrimination, physiological dysregulation, health behaviors, and cognitive performance using the Cognitive Ability Screening Instrument (CASI) at Exam 5 (2010-12) and Exam 6 (2016-18). We examined the relationship between discrimination at Exam 1 (2000-02) and physiological dysregulation at Exam 5. We used overall and ethnoracial-stratified path analysis. All models were adjusted for age, sex, site, depression, stress, socioeconomic status, and APOE-e4.ResultsPhysiological dysregulation was associated with worse cognitive performance in the full sample and among the White ethnoracial subgroup. Everyday discrimination was associated with better cognitive performance among Black participants.DiscussionAssociations between discrimination, physiological dysregulation, and cognitive performance vary and should be examined longitudinally.

The pivotal role of sleep in mediating the effects of life stressors and healthy habits on allostatic load in mid-life adults

Objectives

We assessed the modulation of allostatic load (AL) by engagement in healthy habits and life stressors, mediated through resilience and the perceived influence of the stressors. Sleep was included as third mediator given extensive evidence associating to all the analysed factors.

Methods

Structural equation models to assess the modulation of AL by either traumatic or psychosocial stressors and healthy habits were generated with data from 620 mid-life adults (age 51.3 ± 5.48 years). Model 1 included self-reported life stressors, engagement in cognitive and physical activities, resilience and a pyramid score for diet. In Model 2, self-reported sleep quality was included in the mediation analysis between resilience and perceived stress on AL.

Results

Direct effects of sports and diet on AL, and on resilience by sports were found in all the evaluated models. The modulation of AL by both types of stressors was only revealed in model 2, through indirect effects of perceived influence via sleep quality. An effect of sport habits on AL via resilience was found to be mediated by sleep, and equivalent but opposed effects of perceived influence of stressors and resilience on sleep quality emerged as critical factor for AL modulation.

Conclusion

Our results suggest that sleep plays a pivotal role in the modulation of AL by both life stressors and sport habits, balancing the harmful and protective effects of perceived stress and resilience. The relative weight of one over the other to worsen or improve sleep quality will determine the resulting level of AL.

What Explains the Link Between Hearing and Vision Impairment and Cognitive Function? Analysis of Mediating Effects in the USA, England and Ireland

OBJECTIVES

Hearing and vision impairments are associated with cognitive decline and dementia risk. Explanations for this include age-related processes impacting on sensory and cognitive function (common cause), or sensory impairments having a direct or indirect impact on cognition via social engagement, depression and physical activity (cascade). We tested whether associations between hearing, vision and episodic memory were mediated by allostatic load, social engagement, depression and physical activity.

METHODS

We used structural equation modelling with cross-sectional data from the USA (n = 4746, aged 50-101), England (n = 4907, aged 50-89) and Ireland (4292, aged 50-80) to model factors related to the common cause (indexed by allostatic load) and the cascade hypothesis with respect to cognitive ability (episodic memory).

RESULTS

Poorer hearing/vision was associated with lower social engagement, depression and sedentary lifestyle. Poor vision was not related to allostatic load, and poor hearing was associated with allostatic load in only one data set, contributing to a common-cause hypothesis. Lower social engagement, depression and a sedentary lifestyle were associated with poorer episodic memory, contributing to the cascade hypothesis. Using effect estimates to calculate the proportion of the total effects mediated by the combined mediator variables, up to two fifths of the relationship between hearing and vision with episodic memory can be explained by the mediators.

CONCLUSIONS

The association between hearing, vision and episodic memory is mediated by allostatic load, social engagement, depression, and physical activity. The finding that social engagement, depression, and physical activity mediate the association between sensory abilities and cognitive function supported the cascade hypotheses. Interventions to improve healthy lifestyle, reduce depression and foster social engagement of older people with sensory impairments are likely to be beneficial in preventing cognitive decline and dementia.

Allostatic load measures in older adults with subjective cognitive decline and mild cognitive impairment: A cross-sectional analysis from the Brazilian Memory and Aging Study

INTRODUCTION

An increasing body of research suggests that stress and allostatic load are related to cognitive dysfunction and neurodegeneration.

OBJECTIVES

to determine the relationship between allostatic load (AL) and cognitive status in older adults classified with subjective cognitive decline (SCD) and mild cognitive impairment (MCI).

METHODOLOGY

Using the Brazilian Memory and Aging Study (BRAMS) database, we analyzed data from 57 older adults with SCD and MCI. Blood neuroendocrine (cortisol, DHEA-s), inflammatory (C-reactive protein, fibrinogen), metabolic (HbA1c, HDL-cholesterol, total cholesterol, creatinine), and cardiovascular (blood pressure, waist/hip ratio) were transformed into an AL index.

RESULTS

Despite a significant difference in the univariate analysis between waist/hip ratio (0.94 in the MCI group vs. 0, 88 in the SCD group, p = 0.03), total cholesterol levels (194 vs. 160, p = 0.02), and AL index (36.9 % in the MCI group vs. 27.2 % in the SCD group, p = 0.04), AL was not associated with SCD or MCI in the multivariate analysis.

CONCLUSION

Our data suggest that different profiles of AL in MCI compared to individuals with SCD could be due to cofounding factors. These findings need to be confirmed in longitudinal studies investigating profiles of AL changes at preclinical and prodromal stages of Alzheimer's disease.

Association between allostatic load and accelerated white matter brain aging: findings from the UK Biobank

White matter (WM) brain age, a neuroimaging-derived biomarker indicating WM microstructural changes, helps predict dementia and neurodegenerative disorder risks. The cumulative effect of chronic stress on WM brain aging remains unknown. In this study, we assessed cumulative stress using a multi-system composite allostatic load (AL) index based on inflammatory, anthropometric, respiratory, lipidemia, and glucose metabolism measures, and investigated its association with WM brain age gap (BAG), computed from diffusion tensor imaging data using a machine learning model, among 22 951 European ancestries aged 40 to 69 (51.40% women) from UK Biobank. Linear regression, Mendelian randomization, along with inverse probability weighting and doubly robust methods, were used to evaluate the impact of AL on WM BAG adjusting for age, sex, socioeconomic, and lifestyle behaviors. We found increasing one AL score unit significantly increased WM BAG by 0.29 years in association analysis and by 0.33 years in Mendelian analysis. The age- and sex-stratified analysis showed consistent results among participants 45-54 and 55-64 years old, with no significant sex difference. This study demonstrated that higher chronic stress was significantly associated with accelerated brain aging, highlighting the importance of stress management in reducing dementia and neurodegenerative disease risks.

Allostatic Load in Childhood, Adolescence, and Young Adulthood: Are Assumptions of Measurement Invariance Warranted?

OVERVIEW

Allostatic load represents the cumulative toll of chronic mobilization of the body's stress response systems, as indexed by biomarkers. Higher levels of stress and disadvantage predict higher levels of allostatic load, which, in turn, predict poorer physical and mental health outcomes. To maximize the efficacy of prevention efforts, screening for stress- and disadvantage-associated health conditions must occur before middle age-that is, during childhood, adolescence, and young adulthood. However, this requires that models of allostatic load display properties of measurement invariance across age groups. Because most research on allostatic load has featured older adults, it is unclear if these requirements can be met.

METHODS

To address this question, we fit a series of exploratory and confirmatory analytic models to data on eight biomarkers using a nationally representative sample of N = 4260 children, adolescents, and young adults drawn from the National Health and Nutrition Examination Survey dataset.

RESULTS

Exploratory and confirmatory models indicated that, consistent with allostatic load theory, a unidimensional model was a good fit to the data. However, this model did not display properties of measurement invariance; post-hoc analyses suggested that the biomarkers included in the final confirmatory model were most strongly intercorrelated among young adults and most weakly intercorrelated among adolescents.

CONCLUSIONS

These results underscore the importance of testing assumptions about measurement invariance in allostatic load before drawing substantive conclusions about stress, disadvantage, and health by directly comparing levels of allostatic load across different stages of development, while underscoring the need to expand investigations of measurement invariance to samples of longitudinal data.

The interrelationships of hearing function, allostatic load, and cognitive function: Evidence among middle-aged and older Chinese adults

OBJECTIVES

We aim to examine the interrelationships of self-reported hearing function, allostatic load (AL), and cognitive function among middle aged and older adults.

METHODS

Our data were collected from two waves of the China Health and Retirement Longitudinal Study (CHARLS) conducted in 2011 and 2015. The participants' hearing function was measured using self-rated subjective hearing function. Allostatic load (AL) was evaluated by measuring 14 biomarkers associated with physiological health, which were derived from blood samples. Cognitive function was assessed using three domains: episodic memory, mental intactness, and global cognition. To examine the relationships between hearing function, AL, and cognitive function, path analysis with structural equation modeling (SEM) methodology was employed.

RESULTS

Among individuals aged 60 and above non-hearing aids users, the hearing function at Time 1 (T1) in 2011 has a significant association with the level of AL at T1 (β = 0.02, p < 0.001), as well as on cognitive function at Time 2 (T2) in 2015 (β = -0.1, p < 0.001). Additionally, the AL related to the hearing function at T1 associates an increased risk of AL at T2 (β = 0.5, p < 0.001), and is significantly associated with a decrease of cognitive function scores at T2 (β = -0.4, p < 0.001). However, no significant relationship was found among individuals aged 45 - 59 with non-hearing aids utilizers. Similar findings were in the domains of epidemic memory and mental intactness for cognitive function.

CONCLUSIONS

There were interrelationships of subjective hearing function, AL, and cognitive function among aged 60 years and above, but not among those aged 45-59 years old. It may provide valuable insights for identifying subclinical thresholds in the physiological systems of individuals at risk of pathology in cognitive function.

Comprehensive allostatic load risk index is associated with increased frontal and left parietal white matter hyperintensities in mid-life cognitively healthy adults

To date, there is a considerable heterogeneity of methods to score Allostatic Load (AL). Here we propose a comprehensive algorithm (ALCS) that integrates commonly used approaches to generate AL risk categories and assess associations to brain structure deterioration. In a cohort of cognitively normal mid-life adults (n = 620, age 51.3 ± 5.48 years), we developed a comprehensive composite for AL scoring incorporating gender and age differences, high quartile approach, clinical reference values, and current medications, to then generate AL risk categories. Compared to the empirical approach (ALES), ALCS showed better model fit criteria and a strong association with age and sex. ALSC categories were regressed against brain and white matter hyperintensity (WMH) volumes. Higher AL risk categories were associated with increased total, periventricular, frontal, and left parietal WMH volumes, also showing better fit compared to ALES. When cardiovascular biomarkers were removed from the ALSC algorithm, only left-frontal WMHV remained associated with AL, revealing a strong vascular burden influencing the index. Our results agree with previous evidence and suggest that sustained stress exposure enhances brain deterioration in mid-life adults. Showing better fit than ALES, our comprehensive algorithm can provide a more accurate AL estimation to explore how stress exposure enhances age-related health decline.

Associations of Allostatic Load with Level of and Change in Cognitive Function Among Middle-Aged and Older Hispanic/Latino Adults: The Study of Latinos-Investigation of Neurocognitive Aging (SOL-INCA)

Background

Higher allostatic load (AL), a multi-system measure of physiological dysregulation considered a proxy for chronic stress exposure, is associated with poorer global cognition (GC) in older non-Hispanic white adults. However, evidence of these associations in middle-aged and older US-based Hispanic/Latino adults is limited.

Objective

To examine associations of AL with level of cognition, performance in cognition 7 years later, and change in cognition over 7 years among middle-aged and older US-based Hispanic/Latino adults.

Methods

We used data (n = 5,799, 45-74 years at baseline) from the Hispanic Community Health Study/Study of Latinos (HCHS/SOL) and SOL-Investigation of Neurocognitive Aging (SOL-INCA). The AL score comprised 16 biomarkers representing cardiometabolic, glucose, cardiopulmonary, parasympathetic, and inflammatory systems (higher scores = greater dysregulation). Cognitive outcomes included GC and individual tests of verbal learning and memory, world fluency (WF), Digit Symbol Substitution (DSS), and Trail Making (Parts A & B). Survey-linear regressions assessed associations of AL with performance in cognition at baseline, 7 years later, and via 7-year cognitive change scores adjusting for sociodemographic characteristics, lifestyle factors, and depressive symptoms.

Results

Higher AL was associated with lower baseline performance in GC and WF; and lower 7-year follow-up performance in these same measures plus DSS and Trail Making Parts A & B. Higher AL was associated with more pronounced 7-year change (reduction) in GC and on WF and DSS tests.

Conclusions

Findings extend previous evidence in predominantly older non-Hispanic white cohorts to show that AL is related to level of and change in GC (as well as WF and DSS) among middle-aged and older US-based Hispanic/Latino adults.

Evidence for an association between allostatic load and multisensory integration in middle-aged and older adults

Multisensory integration, the ability of the brain to integrate information from different sensory modalities, is critical for responding to environmental stimuli. While older adults show changes in multisensory integration with age, the impact of allostatic load (AL) (i.e., the effect of exposure to chronic stress, which can accelerate ageing) on multisensory perception remains understudied. We explored the relationship between multisensory integration and AL in 1,358 adults aged 50+ from The Irish Longitudinal Study on Ageing by performing a Sound Induced Flash Illusion (SIFI) task at multiple audio-visual temporal asynchronies. The AL score was created using a battery of biomarkers representing the activity of four major physiological systems: immunological, cardiovascular, metabolic, and renal. The number of biomarkers for which a participant was categorised in the highest risk quartile using sex-specific cutoffs was used to produce an overall AL score. We accounted for medication use when calculating our AL score. We analysed the accuracy of illusion trials on a SIFI task using generalised logistic mixed effects regression models adjusted for a number of covariates. Observation of cross-sectional and longitudinal results revealed that lower accuracy in integration (i.e., higher SIFI susceptibility with larger temporal asynchronies) was associated with higher AL. This confirmed the distinct patterns of multisensory integration in ageing.

Elucidating individual differences in chronic pain and whole person health with allostatic load biomarkers

Chronic pain is a stressor that affects whole person functioning. Persistent and prolonged activation of the body's stress systems without adequate recovery can result in measurable physiological and neurobiological dysregulation recognized as allostatic load. We and others have shown chronic pain is associated with measures of allostatic load including clinical biomarker composites, telomere length, and brain structures. Less is known regarding how different measures of allostatic load align. The purpose of the study was to evaluate relationships among two measures of allostatic load: a clinical composite and pain-related brain structures, pain, function, and socioenvironmental measures. Participants were non-Hispanic black and non-Hispanic white community-dwelling adults between 45 and 85 years old with knee pain. Data were from a brain MRI, questionnaires specific to pain, physical and psychosocial function, and a blood draw. Individuals with all measures for the clinical composite were included in the analysis (n = 175). Indicating higher allostatic load, higher levels of the clinical composite were associated with thinner insula cortices with trends for thinner inferior temporal lobes and dorsolateral prefrontal cortices (DLPFC). Higher allostatic load as measured by the clinical composite was associated with greater knee osteoarthritis pathology, pain disability, and lower physical function. Lower allostatic load as indicated by thicker insula cortices was associated with higher income and education, and greater physical functioning. Thicker insula and DLPFC were associated with a lower chronic pain stage. Multiple linear regression models with pain and socioenvironmental measures as the predictors were significant for the clinical composite, insular, and inferior temporal lobes. We replicate our previously reported bilateral temporal lobe group difference pattern and show that individuals with high chronic pain stage and greater socioenvironmental risk have a higher allostatic load as measured by the clinical composite compared to those individuals with high chronic pain stage and greater socioenvironmental buffers. Although brain structure differences are shown in individuals with chronic pain, brain MRIs are not yet clinically applicable. Our findings suggest that a clinical composite measure of allostatic load may help identify individuals with chronic pain who have biological vulnerabilities which increase the risk for poor health outcomes.

Longitudinal study of Alzheimer's disease biomarkers, allostatic load, and cognition among memory clinic patients

Background

Allostatic load (AL) is defined as the cumulative dysregulation of neuroendocrine, immunological, metabolic, and cardiovascular systems that increases the susceptibility to stress-related health problems. Several dementia and Alzheimer's disease (AD) risk factors have been identified, yet little is known about the role of AL and its associations with AD biomarkers (e.g., beta-amyloid (Aβ) or tau) and cognitive function among memory clinic patients. Hence, this study aims to assess the association between AL and AD biomarkers, cognitive performance, and cognitive decline after 3-years of follow-up.

Methods

Data from 188 memory clinic patients were derived from the Cortisol and Stress in AD (Co-STAR) study in Sweden. Participants underwent baseline assessments including blood tests for AL measures (including cortisol, thyroid stimulating hormone, cobalamin, homocysteine, leukocytes, glycated hemoglobin, albumin, high-density and low-density lipoprotein cholesterol, triglycerides, and creatinine), cerebrospinal fluid (CSF) sampling for AD biomarkers and neuropsychological tests including five cognitive domains. Linear regressions were conducted, adjusting for age, sex, and education.

Results

Higher AL was associated with lower CSF Aβ1-42 levels (β = -0.175, p = 0.025), reflecting higher brain levels of Aβ1-42. Stratified analyses suggested a significant association among women but not men, although the AL-sex interaction was not statistically significant. AL was not significantly associated with T-tau level (β = -0.030, p = 0.682) and P-tau level (β = 0.091, p = 0.980). There were no significant associations between AL and cognition or cognitive decline after 3 years.

Conclusion

This study showed that higher AL was associated with increased brain amyloid accumulation. This suggests that AL may play a role in AD/dementia pathophysiology. Potential sex-related differences should be assessed in further larger studies.

Allostatic load and physical performance in older adults: Findings from the International Mobility in Aging Study (IMIAS)

OBJECTIVE

This study aimed to evaluate the association between Allostatic Load (AL) and physical performance scores in older adults from four cities in North and South America.

METHODS

In this cross-sectional study, data from 1101 volunteers from three countries (Canada, Brazil, and Colombia) from the International Mobility in Aging Study (IMIAS) were used to evaluate the association between AL index and Short Physical Performance Battery (SPPB) scores. Three multiple linear regression models adjusted by age, Socioeconomic Status (SES), chronic conditions, depression symptoms, and Leganés Cognitive Test (LCT) were developed to estimate the independent association between SPPB and AL. Mediation analysis with 2012 LA data and covariates was performed to access the total, direct, and indirect effects of mediation on SPPB scores from 2016.

RESULTS

AL and SPPB were inversely associated, with older adults with high allostatic load scoring lower on SPPB (β: -0.234, Std: 0.033, p-value: <0.001).  Indirect effects were evidenced between age, SES and chronic conditions with AL and SPPB scores. Chronic conditions also had a total effect on SPPB scores and were also mediated by AL. However, indirect effects of depressive symptoms and LCT on SPPB scores mediated by AL were not observed.

CONCLUSIONS

Findings from this study support that increased AL index determines worse physical performance states after full adjustments. AL has a mediator role between the number of chronic diseases, depressive symptoms, cognitive status and physical performance. Socioeconomic status also influenced physical scores mediated by the AL index.

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.

Depression interacts with allostatic load to predict cognitive decline in middle age

BACKGROUND

Allostatic load (AL) indicates the cumulative impact of stress on homeostatic mechanisms. Depression and AL have been associated with cognitive deficits, but it is unclear if they do so independently.

METHODS

Using data from middle-aged participants in the observational longitudinal Midlife in the United States (MIDUS) study (n = 704, 57.5 % female, 63.8 ± 10.6 years old in 2014), we assessed whether the effect of prior depression (Composite International Diagnostic Interview Short-Form in 1995) on cognitive decline between 2004 and 2013 (composite Z-scores derived from the Brief Test of Adult Cognition by Telephone and the Stop & Go Switch Task) was moderated by AL Z-scores in 2004 (calculated from biomarkers in blood, urine, and electrocardiography).

RESULTS

A significant depression × AL interaction predicted a decline in a composite cognitive score (β = -0.066, SE=0.029, p = 0.024) and executive function (β = -0.068, SE=0.025, p = 0.007). Depression predicted a decline in composite cognition among those with AL Z-scores above - 0.055. AL subdomains of inflammation and lipid metabolism showed evidence of moderation.

CONCLUSION

Middle-aged adults with depression who had higher allostatic load were at greater risk of cognitive decline. Future studies should evaluate whether the interaction predicts incident dementia, and whether interventions targeting depression or elevated AL in people who have both can attenuate cognitive decline.

The association between allostatic load and brain: A systematic review

Allostatic load (AL) refers to prolonged dysregulation related to chronic stress that affects brain regions such as the hippocampus, amygdala, and prefrontal cortex (PFC). Higher levels of AL have been associated with poor health outcomes, including psychiatric disorders, cognitive decline, and chronic somatic conditions. However, still little is known about the relationship between AL and the brain, and the mechanisms explaining the damaging effects of stress-related biological dysregulations. Therefore, we aimed to perform a systematic review of studies investigating the association of the AL index with brain structure and functioning in adult populations. PubMed/MEDLINE, CINAHL, Academic Search Complete and Web of Science were searched from their inception until August, 9th 2021. A total of 13 studies were included in the qualitative synthesis. There was a high between-study heterogeneity with respect to the methods used to calculate the AL index and brain parameters. All studies confirmed the associations between a higher AL index and alterations in various brain areas, especially: 1) the hippocampus, white matter volume, gray matter volume, and density in the older adults; 2) the cortex, fornix, hippocampus and choroid plexus in patients with schizophrenia spectrum disorders; and 3) whole-brain white matter tracts, cortical gray matter volume, and cortical thickness in overweight subjects. Overall, the findings of this systematic review imply that an elevated AL index might be associated with various neurostructural and neurofunctional alterations. Some of these associations may appear regardless of clinical or non-clinical populations being investigated (e.g., white matter tracts), whereas others may appear in specific populations (e.g., cortical thinning in overweight/obesity and schizophrenia spectrum disorders). However, additional studies utilizing a consistent approach to calculating the AL index are needed to extend these findings and indicate populations that are most vulnerable to the damaging effects of AL.

The association between Mediterranean diet adherence and allostatic load in older adults

Allostatic load (AL) is a multisystemic index of biological wear and tear which is associated with poor health outcomes. In recent years, researchers have examined the association between dietary pattern intake and AL; however, no studies to date have examined the relationship between AL and consumption of a Mediterranean diet. Blood and urine samples were collected from 201 community-dwelling older adults who completed a Food Frequency Questionnaire (FFQ). A Mediterranean Diet Score (MDS) was calculated based on previous recommendations and a sex-based AL index was calculated using a count-based approach for 16 biomarkers associated with neuroendocrine, immune, cardiovascular, or metabolic function. It was hypothesized that a higher MDS would be associated with lower AL, and that this association would be particularly robust for the immune and metabolic subcomponents of the AL index. In support of the primary study hypotheses, generalized linear models revealed a significant inverse relationship between MDS and AL (ß = -0.03, P = 0.037). However, subcomponents of the AL model were not significantly associated with MDS. Exploratory sub-group analyses by sex suggested that the association between AL and MDS was more robust in male than in female participants. The current findings are interpreted with caution given the study design and sample characteristics. Nonetheless, these findings contribute to the literature supporting the Mediterranean diet as an important lifestyle behavior that may minimize AL, and therefore support healthy aging.

Increased allostatic load associated with ambient air pollution acting as a stressor: Cross-sectional evidence from the China multi-ethnic cohort study

BACKGROUND

Allostatic load measures the cumulative biological burden imposed by chronic stressors. Emerging experimental evidence supports that air pollution acting as a stressor activates the neuroendocrine system and then produces multi-organ effects, leading to allostatic load. However, relevant epidemiological evidence is limited.

OBJECTIVES

We aim to explore the relationships between chronic exposure to ambient air pollution (PM₁, PM_2.5, PM₁₀, and O₃) and allostatic load in Chinese adults.

METHODS

This cross-sectional study included 85,545 participants aged 30-79 from the baseline data of the China Multi-Ethnic Cohort (CMEC). Ambient air pollution levels were evaluated by a satellite-based random forest approach. The previous three-year average exposure concentrations were calculated for each participant based on the residential address. The outcome allostatic load was identified through the sum of the sex-specific scores of twelve biomarkers belonging to four major categories: cardiovascular, metabolic, anthropometric, and inflammatory parameters. We performed statistical analysis using a doubly robust approach which relies on inverse probability weighting and outcome model to adjust for confounding.

RESULTS

Long-term exposure to ambient air pollution was significantly associated with an increased risk of allostatic load, with relative risk (95% confidence interval) of 1.040 (1.024, 1.057), 1.029 (1. 018, 1. 039), and 1.087 (1.074, 1.101) for each 10 μg/m³ increase in ambient PM_2.5, PM₁₀, and O₃, respectively. No significant relationship was observed between chronic exposure to PM₁ and allostatic load. The associations between air pollution and allostatic load are modified by some intrinsic factors and non-chemical stressors. The people with older, minority, lower education, and lower-income levels had a significantly higher allostatic load induced by air pollution.

CONCLUSIONS

Chronic exposure to ambient PM_2.5, PM₁₀, and O₃ may increase the allostatic load. This finding provides epidemiological evidence that air pollution may be a chronic stressor, leading to widespread physiological burdens.

Alternate-day fasting, a high-sucrose/caloric diet and praziquantel treatment influence biochemical and behavioral parameters during Schistosoma mansoni infection in male BALB/c mice

Schistosoma mansoni-induced granulomas result in severe damage to the host's liver, as well as neurological and metabolic disorders. We evaluated the biochemical and behavioral changes during schistosomiasis under three diet protocols: ad libitum (AL), alternate-day fasting (ADF) and a high-sucrose/caloric diet (HSD). Healthy male BALB/c mice were divided into noninfected, matched infected and infected/treated [praziquantel (PZQ)] groups. Caloric intake and energy efficiency coefficients associated with diets were measured. Behavioral (exploratory and locomotor) and biochemical (glucose, triglycerides, total cholesterol, AST, ALT, ALP, and γ-GT) tests and histological analysis were performed. Fifteen weeks postinfection, HSD and PZQ promoted weight gain, with higher caloric consumption than ADF (p < 0.05), reflecting serum glucose levels and lipid profiles. HSD and PZQ prevented liver dysfunction (AST and ALT) and significantly prevented increases in granuloma area (p < 0.05). HSD and PZQ also significantly improved mouse physical performance in exploratory and locomotor behavior (p < 0.05), reversing the impaired motivation caused by infection. These findings showed that ADF worsened the course of S. mansoni infection, while HSD and PZQ, even with synergistic effects, prevented and/or attenuated biochemical and behavioral impairment from infection.

The Role of Purpose in Life in the Relationship Between Widowhood and Cognitive Decline Among Older Adults in the U.S

OBJECTIVES

The objective of this study was to examine the role of purpose in life in the relationship between widowhood and cognitive decline.

METHODS

This study used a sample of 12,856 respondents (20,408 observations) collected from a national panel survey, the 2006-2014 waves of the Health and Retirement Study (HRS), that sampled older adults aged 50 or older. The study estimated growth-curve models with years since spousal death, purpose in life, and interaction between the two to predict cognition using three measures-total cognition, fluid, and crystallized intelligence scores. We also estimated growth-curve models by sex, race/ethnicity, and education.

RESULTS

While years since spousal death negatively correlated with cognition, purpose in life positively correlated with cognition. Furthermore, purpose in life had a moderating effect on the relationship between years since spousal death and cognition. This effect was found by using total cognition (coef. = 0.0515; z = 2.64; p < 0.01) and fluid intelligence scores (coef. = 0.0576; z = 3.23; p < 0.05). The same effects were salient among females (coef. = 0.0556; z = 2.19; p < 0.05), Whites (coef. = 0.0526; z = 2.52; p < 0.05), and older adults with more education (coef. = 0.0635; z = 2.10; p < 0.05).

CONCLUSION

Higher purpose in life relates to the negative correlations between widowhood and cognition of older adults. Educational programs improving purpose in life are a possible avenue for reducing the adverse effect of widowhood on cognition and warrant future exploration.

Addressing the biological embedding of early life adversities (ELA) among adults through mindfulness: Proposed mechanisms and review of converging evidence

Early life adversities (ELA) are prevalent and have a profound and adverse impact across the lifespan, including on age-related health outcomes, yet interventions to remediate its adverse impact are scarce. This paper presents evidence for mindfulness training to reduce the elevated mental and physical health risks linked to ELA among adults by targeting biological mechanisms of ELA leading to these adverse health outcomes. We first provide a brief overview of ELA, its adverse health impacts, and mechanisms that might be responsible. Next, we review converging evidence that demonstrates that mindfulness training influences key biological pathways involved in ELA-linked negative health consequences, including (a) brain networks involved in self-regulation, (b) immunity and inflammation, (c) telomere biology, and (d) epigenetic modifications. Further, we review preliminary evidence from mindfulness-based trials that focused on populations impacted by ELA. We discuss limitations of this review and provide recommendations for future research. If effective, a mindfulness-based approach could be an important public health strategy for remediating the adverse mental and physical health consequences of ELA.

Adverse childhood experiences and low socioeconomic status with respect to allostatic load in adulthood: A systematic review

Early-life psychosocial stress primes a number of health risk behaviors, and contributes to the development of various mental and somatic disorders in adulthood. It has been reported that adverse childhood experiences (ACEs) and low socioeconomic status (SES) might be associated with allostatic load (AL) in adulthood. In turn, elevated AL index has been found to predict a number of unfavorable health outcomes. Therefore, we aimed to perform a systematic review of studies investigating the association of ACEs and childhood SES with AL in adult populations. Independent online searches covered the publication period up to 20th Jun 2021. A total of 27 studies were included in qualitative synthesis. The majority of eligible studies showed that ACEs (14 out of 19 studies recording ACEs, 73.7%) and low childhood SES (11 out of 12 studies recording childhood SES, 91.7%) are associated with elevated AL in adults. However, several processes were found to mediate or moderate this association. These include educational attainments, social support, health behaviors, adult stress, post-traumatic stress disorder, coping strategies and aging. Moreover, a substantial methodological heterogeneity of approaches to calculating the AL index was observed. Apart from reports from overlapping samples, none of eligible studies used the same set of biomarkers. Findings from this systematic review imply that early-life psychosocial stress might have a lasting impact on biological dysregulations captured by the AL index. Future studies need to explore whether the association between early-life stress and the AL index accounts for the development of specific health outcomes.

Menstrual attitude and social cognitive stress influence autonomic nervous system in women with premenstrual syndrome

The autonomic nervous system (ANS) is activated by stress and is closely related to the female menstrual cycle. Women with premenstrual syndrome (PMS) have an imbalanced ANS response in their premenstrual period. However, no studies have explored the reasons for the differences in ANS response among women. In this study, we investigated how the female menstrual attitude and acute social stress influence the ANS response in women with PMS. First, 277 women [24.35 ± 2.1] were selected to measure the mediating role of women's menstrual attitude between PMS severity and perceived ANS response. Second, participants' (50 women [23.23 ± 1.25] with and 46 women [22.92 ± 2.00] without PMS) heart rate (HR) and HR variability (HRV; reflecting the functioning of ANS) under social stress were measured during various menstrual cycle phases. The results indicated that menstrual attitude (bothersome and predictable) had mediating effects between the degree of PMS and perceived ANS response; when undergoing a high cognitive load (e.g. mental-arithmetic) task, the ANS of the PMS group demonstrated hypo-arousal and delayed recovery in the late luteal phase; Therefore, menstrual attitude could influence female perceived ANS response, which may be a risk factor for PMS. When women with PMS experience high-strength cognitive pressure in the premenstrual period, their ANS showed hypo-arousal and delayed recovery, which may be another risk factor for PMS.

Evaluating measures of allostatic load in adolescents: A systematic review

BACKGROUND

Adolescents can experience heightened stress due to biopsychosocial changes that occur during this developmental stage. The 'wear and tear' of the physiological systems responsible for managing our stress response can lead to dysregulation of these systems, known as allostatic load (AL). AL is commonly measured within adult populations, however, inconsistencies exist across measures used to quantify the effects of stress on health. The aim of this review was to identify variations in measures across AL studies, and to consider how specific measures may be more appropriate for use within adolescent populations.

METHOD

Pubmed, PsycINFO, PsycARTICLES, Academic Search Complete, were searched in July 2020, using search terms 'allostatic load' and 'adolescence'. AL studies (1988-2020) with an adolescent population (age 10-24 years) were included. 354 records were screened by two reviewers and 41 full-text articles were assessed for eligibility.

RESULTS

25 studies were included in final synthesis. Biomarkers of AL ranged from 1 to 14. The most common index of AL consisted of 6 biomarkers; cortisol, epinephrine, norepinephrine, systolic blood pressure, diastolic blood pressure, and body-mass index.

FINDINGS

Defining measures of AL during adolescence may help to identify vulnerabilities specific to adolescents, which may shape their lifelong health trajectories.

Stress-induced aberrations in sensory processing predict worse cognitive outcomes in healthy aging adults

It is well recognized that not all individuals age equivalently, with functional dependence attributable, at least in part, to stress accumulated across the lifespan. Amongst these dependencies are age-related declines in cognitive function, which may be the result of impaired inhibitory processing (e.g., sensory gating). Herein, we examined the unique roles of life and biological stress on somatosensory gating dynamics in 74 adults (22-72 years old). Participants completed a sensory gating paired-pulse electrical stimulation paradigm of the right median nerve during magnetoencephalography (MEG) and data were subjected to advanced oscillatory and time-domain analysis methods. We observed separable mechanisms by which increasing levels of life and biological stress predicted higher oscillatory gating ratios, indicative of age-related impairments in inhibitory function. Specifically, elevations in life stress significantly modulated the neural response to the first stimulation in the pair, while elevations in biological stress significantly modulated the neural response to the second stimulation in the pair. In contrast, neither elevations in life nor biological stress significantly predicted the gating of time-domain neural activity in the somatosensory cortex. Finally, our study is the first to link stress-induced decline in sensory gating to cognitive dysfunction, suggesting that gating paradigms may hold promise for detecting discrepant functional trajectories in age-related pathologies in the future.

Positive Effect of Cognitive Reserve on Episodic Memory, Executive and Attentional Functions Taking Into Account Amyloid-Beta, Tau, and Apolipoprotein E Status

Studies exploring the simultaneous influence of several physiological and environmental factors on domain-specific cognition in late middle-age remain scarce. Therefore, our objective was to determine the respective contribution of modifiable risk/protective factors (cognitive reserve and allostatic load) on specific cognitive domains (episodic memory, executive functions, and attention), taking into account non-modifiable factors [sex, age, and genetic risk for Alzheimer's disease (AD)] and AD-related biomarker amount (amyloid-beta and tau/neuroinflammation) in a healthy late-middle-aged population. One hundred and one healthy participants (59.4 ± 5 years; 68 women) were evaluated for episodic memory, executive and attentional functioning via neuropsychological test battery. Cognitive reserve was determined by the National Adult Reading Test. The allostatic load consisted of measures of lipid metabolism and sympathetic nervous system functioning. The amyloid-beta level was assessed using positron emission tomography in all participants, whereas tau/neuroinflammation positron emission tomography scans and apolipoprotein E genotype were available for 58 participants. Higher cognitive reserve was the main correlate of better cognitive performance across all domains. Moreover, age was negatively associated with attentional functioning, whereas sex was a significant predictor for episodic memory, with women having better performance than men. Finally, our results did not show clear significant associations between performance over any cognitive domain and apolipoprotein E genotype and AD biomarkers. This suggests that domain-specific cognition in late healthy midlife is mainly determined by a combination of modifiable (cognitive reserve) and non-modifiable factors (sex and age) rather than by AD biomarkers and genetic risk for AD.

Mechanisms of Racial Disparities in Cognitive Aging: An Examination of Material and Psychosocial Well-Being

OBJECTIVES

We tested the hypothesis that education's effect on cognitive aging operates in part through measures of material and psychosocial well-being.

METHOD

Our sample was of non-Latino black and white participants of the National Social Life Health and Aging Project who had valid cognitive assessments in Waves 2 and 3 (n = 2,951; age range: 48-95). We used structural equation modeling to test for mediation and moderated mediation by income, assets, perceived stress, social status, and allostatic load on the relationships between race, education, and cognition at two time points.

RESULTS

Education consistently mediated the race-cognition relationship, explaining about 20% of the relationship between race and cognition in all models. Income and assets were moderated by race; these factors were associated with cognition for whites but not blacks. Social status mediated the association between race and cognition, and social status and perceived stress mediated the education-cognition pathway. Allostatic load was not a mediator of any relationship.

DISCUSSION

Education remains the best explanatory factor for cognitive aging disparities, though material well-being and subjective social status help to explain a portion of the racial disparity in cognitive aging.

Relationship between allostatic load and clinical outcomes in youth at ultra-high risk for psychosis in the NEURAPRO study

Individuals at ultra-high risk (UHR) for psychosis have an elevated risk of developing psychosis and other psychiatric outcomes. Risk biomarkers can assist in delineating individual risk and allow better prediction of longer-term outcomes. The aim of the present study was to examine if allostatic load (AL), a multisystem index of neuroendocrine, cardiovascular, immune and metabolic dysregulation, is associated with clinical outcomes in youth at UHR for psychosis. AL was measured in 106 participants of the NEURAPRO study (n = 70 female, n = 36 male; mean age 17.21, SD 2.37), a multicentre randomized-controlled trial of long-chain omega-3 polyunsaturated fatty acids versus placebo in people at UHR for psychosis. Psychiatric symptoms and social and occupational functioning were assessed at baseline and 6 and 12 months after study intake. Multivariate linear and logistic regression models were used to test the relationship between AL and clinical outcomes. High AL at baseline was associated with poor social and occupational functioning at 6 months (β = -0.224, p = 0.025) and with more severe manic symptoms at 6 months (β = 0.207, p = 0.026), taking into account relevant covariates including age and smoking status. No significant associations were observed at the 12-month follow-up assessment or with any other clinical outcome measures. Our data provide initial evidence for a link between AL and impaired functioning in individuals at UHR for psychosis. Further studies are needed to evaluate AL as a potential predictor of early treatment response.

The association between allostatic load and cognitive function: A systematic and meta-analytic review

Previous research suggests that high allostatic load (AL), a biological indicator of physiological dysregulation due to chronic stress, is associated with poor cognitive functioning. To date, no studies have systematically reviewed the literature to evaluate the strength and consistency of this relationship. The objective of this study was to conduct a systematic and meta-analytic review of studies that have investigated the association between AL and performance on standardized cognitive tests among adults aged 18 years and older. A total of 18 studies were retained for review. Meta-analyses revealed a significant cross-sectional association between higher AL and poor global cognition (r = -0.08, p <  0.001) and executive function (r = -0.07, p =  0.02), but not memory (r = -0.07, p =  0.10). Due to variation in statistical methods used, longitudinal meta-analyses were not performed. Qualitative review of the literature suggests that AL algorithm, physiological systems and individual biomarkers included in the AL index, and sample age may be key moderators of the AL-cognition relationship. Although the magnitude of reported associations is small, findings support AL as a robust indicator of cognitive function among adults. Study limitations and future directions are discussed.

Parsing inter- and intra-individual variability in key nervous system mechanisms of stress responsivity and across functional domains

Exposure to stressful events is omnipresent in modern human life, yet people show considerable heterogeneity in the impact of stress exposure(s) on their functionality and overall health. Encounter with stressor(s) is counteracted by an intricate repertoire of nervous-system responses. This narrative review starts with a brief summary of the vast evidence that supports heart rate variability, cortisol secretion, and large-scale cortical network interactions as kay physiological, endocrinological, and neural mechanisms of stress responsivity, respectively. The second section highlights potential sources for inter-individual variability in these mechanisms, by focusing on biological, environmental, social, habitual, and psychological factors that may influence stress responsivity patterns and thus contribute to heterogeneity in the impact of stress exposure on functionality and health. The third section introduces intra-individually variability in stress responsivity across functional domains as a novel putative source for heterogeneity in the impact of stress exposure. Challenges and future directions are further discussed. Parsing inter- and intra-individual variability in nervous-system mechanisms of stress responsivity and across functional domains is critical towards potential clinical translation.

Roles of Gut Microbiota in Pathogenesis of Alzheimer's Disease and Therapeutic Effects of Chinese Medicine

Alzheimer's disease (AD) is the most common neurodegenerative disease characterized by progressive cognitive impairment. The pathogenesis of AD is complex, and its susceptibility and development process are affected by age, genetic and epigenetic factors. Recent studies confirmed that gut microbiota (GM) might contribute to AD through a variety of pathways including hypothalamic pituitary adrenal axis and inflflammatory and immune processes. CM formula, herbs, and monomer enjoy unique advantages to treat and prevent AD. Hence, the purpose of this review is to outline the roles of GM and its core metabolites in the pathogenesis of AD. Research progress of CMs regarding the mechanisms of how they regulate GM to improve cognitive impairment of AD is also reviewed. The authors tried to explore new therapeutic strategies to AD based on the regulation of GM using CM.

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.

Personality and Motoric Cognitive Risk Syndrome

OBJECTIVES

To examine whether five major personality traits are related to the motoric cognitive risk (MCR) syndrome, a pre-dementia syndrome characterized by cognitive complaints and slow gait speed.

DESIGN

Cross-sectional.

SETTING

Health and Retirement Study (HRS) and the National Health and Aging Trends Survey (NHATS).

PARTICIPANTS

Dementia-free older adults aged 65 to 107 years (N > 8000).

MEASUREMENTS

In both samples, participants provided data on personality, cognitive complaints, and measures of gait speed, as well as on demographic factors, physical activity, depressive symptoms, and body mass index (BMI).

RESULTS

Across the two samples and a meta-analysis, higher neuroticism was related to higher risk of MCR (combined odds ratio [OR] = 1.32; 95% confidence interval [CI] = 1.21-1.45; P < .001), whereas higher extraversion (combined OR = .71; 95% CI = .65-.79; P < .001) and conscientiousness (combined OR = .70; 95% CI = .62-.78; P < .001) were associated with a lower likelihood of MCR. Higher openness was also related to a lower risk of MCR in the HRS and the meta-analysis (combined OR = .77; 95% CI = .70-.85; P < .001), whereas agreeableness was protective only in the HRS (OR = .83; 95% CI = .74-.92; P < .001). Additional analyses indicated that physical activity, depressive symptoms, and BMI partially accounted for these associations.

CONCLUSION

This study adds to existing research on the factors related to the risk of MCR by showing an association with personality traits. Personality assessment may help to identify individuals who may be targeted by interventions focused on reducing the risk of MCR and ultimately of dementia. J Am Geriatr Soc 68:803-808, 2020.

The Factor Structure of Cognitive Functioning in Cognitively Healthy Participants: a Meta-Analysis and Meta-Analysis of Individual Participant Data

Many neuropsychologists are of the opinion that the multitude of cognitive tests may be grouped into a much smaller number of cognitive domains. However, there is little consensus on how many domains exist, what these domains are, nor on which cognitive tests belong to which domain. This incertitude can be solved by factor analysis, provided that the analysis includes a broad range of cognitive tests that have been administered to a very large number of people. In this article, two such factor analyses were performed, each combining multiple studies. However, because it was not possible to obtain complete multivariate data on more than the most common test variables in the field, not all possible domains were examined here. The first analysis was a factor meta-analysis of correlation matrices combining data of 60,398 healthy participants from 52 studies. Several models from the literature were fitted, of which a version based on the Cattell-Horn-Carroll (CHC) model was found to describe the correlations better than the others. The second analysis was a factor analysis of the Advanced Neuropsychological Diagnostics Infrastructure (ANDI) database, combining scores of 11,881 participants from 54 Dutch and Belgian studies not included in the first meta-analysis. Again, the model fit was better for the CHC model than for other models. Therefore, we conclude that the CHC model best characterizes both cognitive domains and which test belongs to each domain. Therefore, although originally developed in the intelligence literature, the CHC model deserves more attention in neuropsychology.

Disruption of Neural Homeostasis as a Model of Relapse and Recurrence in Late-Life Depression

The significant public health burden associated with late-life depression (LLD) is magnified by the high rates of recurrence. In this manuscript, we review what is known about recurrence risk factors, conceptualize recurrence within a model of homeostatic disequilibrium, and discuss the potential significance and challenges of new research into LLD recurrence. The proposed model is anchored in the allostatic load theory of stress. We review the allostatic response characterized by neural changes in network function and connectivity and physiologic changes in the hypothalamic-pituitary-adrenal axis, autonomic nervous system, immune system, and circadian rhythm. We discuss the role of neural networks' instability following treatment response as a source of downstream disequilibrium, triggering and/or amplifying abnormal stress response, cognitive dysfunction and behavioral changes, ultimately precipitating a full-blown recurrent episode of depression. We propose strategies to identify and capture early change points that signal recurrence risk through mobile technology to collect ecologically measured symptoms, accompanied by automated algorithms that monitor for state shifts (persistent worsening) and variance shifts (increased variability) relative to a patient's baseline. Identifying such change points in relevant sensor data could potentially provide an automated tool that could alert clinicians to at-risk individuals or relevant symptom changes even in a large practice.

The Face of Early Cognitive Decline? Shape and Asymmetry Predict Choice Reaction Time Independent of Age, Diet or Exercise

Slower reaction time is a measure of cognitive decline and can occur as early as 24 years of age. We are interested if developmental stability predicts cognitive performance independent of age and lifestyle (e.g., diet and exercise). Developmental stability is the latent capacity to buffer ontogenetic stressors and is measured by low fluctuating asymmetry (FA). FA is random—with respect to the largest side—departures from perfect morphological symmetry. The degree of asymmetry has been associated with physical fitness, morbidity, and mortality in many species, including humans. We expected that low FA (independent of age, diet and exercise) will predict faster choice reaction time (i.e., correct keyboard responses to stimuli appearing in a random location on a computer monitor). Eighty-eight university students self-reported their fish product consumption, exercise, had their faces 3D scanned and cognitive performance measured. Unexpectedly, increased fish product consumption was associated with worsened choice reaction time. Facial asymmetry and multiple face shape variation parameters predicted slower choice reaction time independent of sex, age, diet or exercise. Future work should develop longitudinal interventions to minimize early cognitive decline among vulnerable people (e.g., those who have experienced ontogenetic stressors affecting optimal neurocognitive development).

Trajectories of cognitive decline by widowhood status among Korean older adults

OBJECTIVES

Given the limited evidence regarding the longitudinal impact of widowhood on cognitive function in later life, the present study aimed to investigate the longitudinal effect of widowhood status on cognitive change among Korean older adults.

METHODS

The study sample was drawn from a nationally representative data set, the Korean Longitudinal Study of Ageing (KLoSA); it consisted of 3,660 Korean adults aged 60 and over who were married at baseline. Our dependent variable, cognitive function, was measured by the Korean version of the Mini-Mental State Examination (K-MMSE). Widowhood status was measured with the combination of widowhood status and duration. Growth curve models were constructed using five waves of the KLoSA (2006-2014) to examine the longitudinal trajectories of cognitive changes.

RESULTS

In the unadjusted model, widowed older adults had significantly lower cognitive function than their nonwidowed counterparts regardless of widowhood duration. Adjusting for covariates, results from the growth curve models showed that widowed older adults with widowhood duration 4 to 6 years had a significantly steeper decline in cognitive function than nonwidowed older adults (P < 0.05).

CONCLUSIONS

These findings suggest that widowhood is detrimental for late-life cognitive function. Further research is required to understand the mechanisms underlying this relationship. Policy and practice implications are discussed according to the cultural context.

Allostatic load and executive functions in overweight adults

BACKGROUND/OBJECTIVE

Overweight is linked to inflammatory and neuroendocrine responses potentially prompting deregulations in biological systems harmful to the brain, particularly to the prefrontal cortex. This structure is crucial for executive performance, ultimately supervising behaviour. Thus, in the present work, we aimed to test the relationship between allostatic load increase, a surrogate of chronic physiological stress, and core executive functions, such as cognitive flexibility, inhibitory control, and working memory.

METHOD

Forty-seven healthy-weight and 56 overweight volunteers aged from 21 to 40 underwent medical and neuropsychological examination.

RESULTS

Overweight subjects exhibited a greater allostatic load index than healthy-weight individuals. Moreover, the allostatic load index was negatively related to inhibitory control. When separated, the link between allostatic load index and cognitive flexibility was more marked in the overweight group.

CONCLUSIONS

An overweight status was linked to chronic physiological stress. The inverse relationship between the allostatic load index and cognitive flexibility proved stronger in this group. Set-shifting alterations could sustain rigid-like behaviours and attitudes towards food.

State inequality, socioeconomic position and subjective cognitive decline in the United States

BACKGROUND

Social gradients in health have been observed for many health conditions and are suggested to operate through the effects of status anxiety. However, the gradient between education and Alzheimer's disease is presumed to operate through cognitive stimulation. We examined the possible role of status anxiety through testing for state-level income inequality and social gradients in markers of socioeconomic position (SEP) for Alzheimer's disease risk.

METHODS

Using data from the cross-sectional 2015 and 2016 Behavioral Risk Factor Surveillance System (BRFSS) and the U.S. Census Bureau's American Community Survey, we tested for the association between U.S. state-level income inequality and individual SEP on subjective cognitive decline (SCD) - a marker of dementia risk - using a generalized estimating equation and clustering by state.

RESULTS

State income inequality was not significantly associated with SCD in our multivariable model (OR 1.2; 95% CI: 0.9, 1.6; p=0.49). We observed a clear linear relationship between household income and SCD where those with an annual household income of 50k to 75k had 1.4 (95% CI: 1.3, 1.6) times the odds and those with household incomes of less than $10,000 had 4.7 (95% CI: 3.8, 5.7) times the odds of SCD compared to those with household income of more than $75,000. We also found that college graduates (ref.) and those who completed high school (OR: 1.1; 95% CI 1.04, 1.2) fared better than those with some college (OR: 1.3, 95% CI 1.2, 1.4) or less than a high school degree (OR: 1.5; 95% CI: 1.4, 1.7).

CONCLUSIONS

Income inequality does not play a dominant role in SCD, though a social gradient in individual income for SCD suggests the relationship may operate in part via status anxiety.

Psychobiological factors of resilience and depression in late life

In contrast to traditional perspectives of resilience as a stable, trait-like characteristic, resilience is now recognized as a multidimentional, dynamic capacity influenced by life-long interactions between internal and environmental resources. We review psychosocial and neurobiological factors associated with resilience to late-life depression (LLD). Recent research has identified both psychosocial characteristics associated with elevated LLD risk (e.g., insecure attachment, neuroticism) and psychosocial processes that may be useful intervention targets (e.g., self-efficacy, sense of purpose, coping behaviors, social support). Psychobiological factors include a variety of endocrine, genetic, inflammatory, metabolic, neural, and cardiovascular processes that bidirectionally interact to affect risk for LLD onset and course of illness. Several resilience-enhancing intervention modalities show promise for the prevention and treatment of LLD, including cognitive/psychological or mind-body (positive psychology; psychotherapy; heart rate variability biofeedback; meditation), movement-based (aerobic exercise; yoga; tai chi), and biological approaches (pharmacotherapy, electroconvulsive therapy). Additional research is needed to further elucidate psychosocial and biological factors that affect risk and course of LLD. In addition, research to identify psychobiological factors predicting differential treatment response to various interventions will be essential to the development of more individualized and effective approaches to the prevention and treatment of LLD.

How stress mediators can cumulatively contribute to Alzheimer's disease An allostatic load approach

Allostatic load is defined as the frequent activation of the neuroendocrine, immunological, metabolic and cardiovascular systems, which makes individuals more susceptible to stress-related health problems. According to this model, physiological dysregulations start to emerge decades before diseases manifest. Consequently, stress research has shifted its attention to anticipating the degree of this dysregulation to better understand the impact of stress hormones and other biomarkers on disease progression. In view of the growing number of studies that demonstrate the influence of modifiable risk factors on cognitive decline, in addition to the effects of chronic stress mediators, the objective of the present review was to present an overview of the development of cognitive changes based on studies on stress and its mediators.

Allostatic load and disordered white matter microstructure in overweight adults

Overweight and stress are both related to brain structural abnormalities. The allostatic load model states that frequent disruption of homeostasis is inherently linked to oxidative stress and inflammatory responses that in turn can damage the brain. However, the effects of the allostatic load on the central nervous system remain largely unknown. The current study aimed to assess the relationship between the allostatic load and the composition of whole-brain white matter tracts in overweight subjects. Additionally, we have also tested for grey matter changes regarding allostatic load increase. Thirty-one overweight-to-obese adults and 21 lean controls participated in the study. Our results showed that overweight participants presented higher allostatic load indexes. Such increases correlated with lower fractional anisotropy in the inferior fronto-occipital fasciculi and the right anterior corona radiata, as well as with grey matter reductions in the left precentral gyrus, the left lateral occipital gyrus, and the right pars opercularis. These results suggest that an otherwise healthy overweight status is linked to long-term biological changes potentially harmful to the brain.

Parental socioeconomic position and midlife allostatic load: a study of potential mediators

BACKGROUND

The mechanisms underlying the association of parental socioeconomic position with later life allostatic load remain unclear. The present study aims to examine potential pathways underlying this association: personality, social relations, intelligence and education.

METHODS

The study comprised 361 members of the Copenhagen Perinatal Cohort who participated in two subsequent follow-ups: the Prenatal Development Project (mean age 27 years) and the Copenhagen Aging and Midlife Biobank study (mean age 50 years). Allostatic load was based on 14 biomarkers representing the inflammatory, metabolic and cardiovascular system measured at midlife. Information on potential mediators was collected in young adulthood, and their role in the association of parental socioeconomic position with midlife allostatic load were examined in linear regression path analyses.

RESULTS

Parental socioeconomic position at one year was inversely associated with midlife allostatic load (β = - 0.238, p < .001). No mediation effects were found for personality or social relations. In a model including intelligence and education, a significant indirect effect was found for education (β = - 0.151, p < .001). A significant direct effect remained (β = - 0.111, p = .040).

CONCLUSIONS

Parental socioeconomic position was inversely associated with allostatic load in midlife. Results suggest that part of this association was mediated by education. A better understanding of the non-cognitive pathways related to education is an important prerequisite for the development of effective intervention strategies.