Aging and Positive Mood: Longitudinal Neurobiological and Cognitive Correlates

More organized white matter is associated with positivity bias in older adults

On average, healthy older adults prefer positive over neutral or negative stimuli. This positivity bias is related to memory and attention processes and is linked to the function and structure of several interconnected brain areas. However, the relationship between the positivity bias and white matter integrity remains elusive. The present study examines how white matter organization relates to the degree of the positivity bias among older adults. We collected imaging and behavioral data from 25 individuals (12 females, 13 males, and a mean age of 77.32). Based on a functional memory task, we calculated a Pos-Neg score, reflecting the memory for positively valenced information over negative information, and a Pos-Neu score, reflecting the memory for positively valenced information over neutral information. Diffusion-weighted magnetic resonance imaging data were processed using Tract-Based Spatial Statistics. We performed two non-parametric permutation tests to correlate whole brain white matter integrity and the Pos-Neg and Pos-Neu scores while controlling for age, sex, and years of education. We observed a statistically significant positive association between the Pos-Neu score and white matter integrity in multiple brain connections, mostly frontal. The results did not remain significant when including verbal episodic memory as an additional covariate. Our study indicates that the positivity bias in memory in older adults is associated with more organized white matter in the connections of the frontal brain. While these frontal areas are critical for memory and executive processes and have been related to pathological aging, more extensive studies are needed to fully understand their role in the positivity bias and the potential for therapeutic interventions.

Research status and global trends of late-life depression from 2004 to 2023: bibliometric analysis

Background

Global research hotspots and future research trends in the neurobiological mechanisms of late-life depression (LLD) as well as its diagnosis and treatment are not yet clear.

Objectives

This study profiled the current state of global research on LLD and predicted future research trends in the field.

Methods

Literature with the subject term LLD was retrieved from the Web of Science Core Collection, and CiteSpace software was used to perform econometric and co-occurrence analyses. The results were visualized using CiteSpace, VOSviewer, and other software packages.

Results

In total, 10,570 publications were included in the analysis. Publications on LLD have shown an increasing trend since 2004. The United States and the University of California had the highest number of publications, followed consecutively by China and England, making these countries and institutions the most influential in the field. Reynolds, Charles F. was the author with the most publications. The International Journal of Geriatric Psychiatry was the journal with the most articles and citations. According to the co-occurrence analysis and keyword/citation burst analysis, cognitive impairment, brain network dysfunction, vascular disease, and treatment of LLD were research hotspots.

Conclusion

Late-life depression has attracted increasing attention from researchers, with the number of publications increasing annually. However, many questions remain unaddressed in this field, such as the relationship between LLD and cognitive impairment and dementia, or the impact of vascular factors and brain network dysfunction on LLD. Additionally, the treatment of patients with LLD is currently a clinical challenge. The results of this study will help researchers find suitable research partners and journals, as well as predict future hotspots.

An Executive Functioning Composite Does Not Moderate the Relationship Between Combat Exposure and Posttraumatic Stress Disorder Symptom Clusters

OBJECTIVE

Posttraumatic stress disorder (PTSD) is prevalent among U.S. combat Veterans, and associated with poor health and wellbeing. As combat experiences are likely to significantly modify self-, other-, and society-oriented cognitions and heighten risk for PTSD, examination of related cognitive processes may yield new treatment strategies. The cognitive model of PTSD suggests that persistent threat perceptions contribute to symptom worsening. Thus, cognitive processes of shifting perspectives or generating novel interpretations may be particularly relevant to lessen PTSD symptoms. This cross-sectional study examined executive functioning as a moderator to the relationship between combat exposure and PTSD symptom clusters among post-9/11 Veterans.

METHOD

Data from 168 Veterans were drawn from a larger study examining post-deployment mental health and cognitive function. An executive functioning composite derived from Wisconsin Card Sorting Test Perseveration Errors, WAIS-III Similarities, Trail Making Test B, and Stroop Color-Word Inhibition scores was computed. Path analysis was used to test the moderation model.

RESULTS

After accounting for age, sex, and estimated premorbid functioning, results indicated that combat exposure was associated with all symptom clusters on the PTSD Checklist-Military. Executive functioning was not significantly associated with the PTSD symptom clusters and did not moderate the relationship between combat exposure and any of the PTSD symptom clusters.

CONCLUSIONS

Combat exposure is an important dimension of risk related to PTSD in Veterans that warrants regular screening. Moderation by executive functioning was not observed despite theoretical support. Future work could test methodological and sampling reasons for this finding to determine if theoretical adjustment is necessary.

Engineering Virtuous health habits using Emotion and Neurocognition: Flexibility for Lifestyle Optimization and Weight management (EVEN FLOW)

Interventions to preserve functional independence in older adults are critically needed to optimize 'successful aging' among the large and increasing population of older adults in the United States. For most aging adults, the management of chronic diseases is the most common and impactful risk factor for loss of functional independence. Chronic disease management inherently involves the learning and adaptation of new behaviors, such as adopting or modifying physical activity habits and managing weight. Despite the importance of chronic disease management in older adults, vanishingly few individuals optimally manage their health behavior in the service of chronic disease stabilization to preserve functional independence. Contemporary conceptual models of chronic disease management and health habit theory suggest that this lack of optimal management may result from an underappreciated distinction within the health behavior literature: the behavioral domains critical for initiation of new behaviors (Initiation Phase) are largely distinct from those that facilitate their maintenance (Maintenance Phase). Psychological factors, particularly experiential acceptance and trait levels of openness are critical to engagement with new health behaviors, willingness to make difficult lifestyle changes, and the ability to tolerate aversive affective responses in the process. Cognitive factors, particularly executive function, are critical to learning new skills, using them effectively across different areas of life and contextual demands, and updating of skills to facilitate behavioral maintenance. Emerging data therefore suggests that individuals with greater executive function are better able to sustain behavior changes, which in turn protects against cognitive decline. In addition, social and structural supports of behavior change serve a critical buffering role across phases of behavior change. The present review attempts to address these gaps by proposing a novel biobehavioral intervention framework that incorporates both individual-level and social support system-level variables for the purpose of treatment tailoring. Our intervention framework triangulates on the central importance of self-regulatory functioning, proposing that both cognitive and psychological mechanisms ultimately influence an individuals' ability to engage in different aspects of self-management (individual level) in the service of maintaining independence. Importantly, the proposed linkages of cognitive and affective functioning align with emerging individual difference frameworks, suggesting that lower levels of cognitive and/or psychological flexibility represent an intermediate phenotype of risk. Individuals exhibiting self-regulatory lapses either due to the inability to regulate their emotional responses or due to the presence of executive functioning impairments are therefore the most likely to require assistance to preserve functional independence. In addition, these vulnerabilities will be more easily observable for individuals requiring greater complexity of self-management behavioral demands (e.g. complexity of medication regimen) and/or with lesser social support. Our proposed framework also intuits several distinct intervention pathways based on the profile of self-regulatory behaviors: we propose that individuals with intact affect regulation and impaired executive function will preferentially respond to 'top-down' training approaches (e.g., strategy and process work). Individuals with intact executive function and impaired affect regulation will respond to 'bottom-up' approaches (e.g., graded exposure). And individuals with impairments in both may require treatments targeting caregiving or structural supports, particularly in the context of elevated behavioral demands.

Poorer aging trajectories are associated with elevated serotonin synthesis capacity

The dorsal raphe nucleus (DRN) is one of the earliest targets of Alzheimer's disease-related tau pathology and is a major source of brain serotonin. We used [18F]Fluoro-m-tyrosine ([18F]FMT) PET imaging to measure serotonin synthesis capacity in the DRN in 111 healthy adults (18-85 years-old). Similar to reports in catecholamine systems, we found elevated serotonin synthesis capacity in older adults relative to young. To establish the structural and functional context within which serotonin synthesis capacity is elevated in aging, we examined relationships among DRN [18F]FMT net tracer influx (Ki) and longitudinal changes in cortical thickness using magnetic resonance imaging, longitudinal changes in self-reported depression symptoms, and AD-related tau and β-amyloid (Aβ) pathology using cross-sectional [18F]Flortaucipir and [11C]Pittsburgh compound-B PET respectively. Together, our findings point to elevated DRN [18F]FMT Ki as a marker of poorer aging trajectories. Older adults with highest serotonin synthesis capacity showed greatest temporal lobe cortical atrophy. Cortical atrophy was associated with increasing depression symptoms over time, and these effects appeared to be strongest in individuals with highest serotonin synthesis capacity. We did not find direct relationships between serotonin synthesis capacity and AD-related pathology. Exploratory analyses revealed nuanced effects of sex within the older adult group. Older adult females showed the highest DRN synthesis capacity and exhibited the strongest relationships between entorhinal cortex tau pathology and increasing depression symptoms. Together these findings reveal PET measurement of the serotonin system to be a promising marker of aging trajectories relevant to both AD and affective changes in older age.

Roles of physical activity and diet in cognitive aging: is more better?

Objective: To determine the synergistic effects of nutrition, specifically adherence to the Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) diet, and physical activity on cognition and brain outcomes in a cross-sectional healthy aging cohort. Methods: A total of 132 adults (age range 52-91; Clinical Dementia Rating = 0) from the UCSF Brain Aging Project completed a 15-item MIND diet food frequency questionnaire and an 11-item self-report measure of weekly physical activity (Physical Activity Scale [PASE]). Cognitive outcomes included executive functioning, episodic memory, and language. Neuroimaging outcomes consisted of total grey matter volume and total white matter volume, adjusted for total intracranial volumes. All regression interaction models adjusted for age, sex, education, and a composite vascular burden score. Results: There was a significant interaction between PASE and MIND on executive functioning and total grey matter volume. Low levels of both related to disproportionately poorer cognitive and brain structural outcomes. Increasing levels of either, but not both, PASE or MIND related to better executive functioning and gray matter outcomes. For memory, language, and total white matter volume, the interaction between PASE and MIND showed the same directionality but did not reach statistical significance. Conclusions: Higher levels of physical activity associated with better executive functioning and gray matter volume, particularly when diet was poor. Similarly, higher levels of MIND diet adherence were associated with better brain and cognitive outcomes when physical activity was low. However, highest levels of physical activity and MIND diet together did not necessarily lead to disproportionately better cognitive and brain volume outcomes.

The aging mind: A complex challenge for research and practice

Cognitive decline as part of mental ageing is typically assessed with standardized tests; below-average performance in such tests is used as an indicator for pathological cognitive aging. In addition, morphological and functional changes in the brain are used as parameters for age-related pathological decline in cognitive abilities. However, there is no simple link between the trajectories of changes in cognition and morphological or functional changes in the brain. Furthermore, below-average test performance does not necessarily mean a significant impairment in everyday activities. It therefore appears crucial to record individual everyday tasks and their cognitive (and other) requirements in functional terms. This would also allow reliable assessment of the ecological validity of existing and insufficient cognitive skills. Understanding and dealing with the phenomena and consequences of mental aging does of course not only depend on cognition. Motivation and emotions as well personal meaning of life and life satisfaction play an equally important role. This means, however, that cognition represents only one, albeit important, aspect of mental aging. Furthermore, creating and development of proper assessment tools for functional cognition is important. In this contribution we would like to discuss some aspects that we consider relevant for a holistic view of the aging mind and promote a strengthening of a multidisciplinary approach with close cooperation between all basic and applied sciences involved in aging research, a quick translation of the research results into practice, and a close cooperation between all disciplines and professions who advise and support older people.

The causal association between empty nest and depressive symptoms with cognitive impairments in China

BACKGROUND

In the context of rapid aging, "empty nest syndrome" is becoming a major public health concern. The causal effects of empty nest on depressive symptoms have been studied in developed countries, but the mediating mechanism of depressive symptoms in the association between empty nest and cognitive impairments has not been studied. This study estimated the causal association of empty nest with depressive symptoms and cognitive impairments in China, and then estimated how depression mediates the association between empty nest and cognitive impairments.

METHODS

Using data of 23,614 urban older adults (65+) obtained from the Shandong Province Aging and Mental Health Survey in 2020, a weighted linear regression model combined with instrumental variable was applied to explore the causal effects of empty nest, and a four-step mediation model was run to test the mediator of depressive symptoms. The Ascertain Dementia 8-item Questionnaire and Patient Health Questionnaire-9 were used to measure cognitive impairments and depressive symptoms.

RESULTS

Empty nest was associated with 0.13 (95%CI: 0.04-0.23) and 0.23 (95%CI: 0.14-0.33) increases in the Ascertain Dementia 8-item Questionnaire and the Patient Health Questionnaire-9 scores, respectively. The association between empty nest and the Ascertain Dementia 8-item Questionnaire scores was mediated by the Patient Health Questionnaire-9 scores.

CONCLUSIONS

Empty nest affected depression in adulthood with cognitive impairments. A focus on integrative intervention for empty nesters is recommended, taking depression and cognition into account.

LIMITATIONS

It is a cross-sectional study and the data is not nationally representative.

Brain-based mechanisms of late-life depression: Implications for novel interventions

Late-life depression (LLD) is a particularly debilitating illness. Older adults suffering from depression commonly experience poor outcomes in response to antidepressant treatments, medical comorbidities, and declines in daily functioning. This review aims to further our understanding of the brain network dysfunctions underlying LLD that contribute to disrupted cognitive and affective processes and corresponding clinical manifestations. We provide an overview of a network model of LLD that integrates the salience network, the default mode network (DMN) and the executive control network (ECN). We discuss the brain-based structural and functional mechanisms of LLD with an emphasis on their link to clinical subtypes that often fail to respond to available treatments. Understanding the brain networks that underlie these disrupted processes can inform the development of targeted interventions for LLD. We propose behavioral, cognitive, or computational approaches to identifying novel, personalized interventions that may more effectively target the key cognitive and affective symptoms of LLD.

Stress and aging: A neurovisceral integration perspective

Darwin emphasized the intimate relationship between the brain and the heart over 150 years ago. Healthy aging is associated with significant changes in both the brain and the heart. The changes between these, the two most important organs of the body, are linked via the vagus nerve. In this review, we examine the normative changes with aging and the effect that stress may have on how the brain-heart connection changes with age. We provide a framework based on the concept of neurovisceral integration and propose that stress regulation is emotion regulation. As such, studies that have investigated emotion regulation may yield insights into successful stress regulation that helps protect people from age-related decline. In addition, interventions that improve brain health also improve heart health and vice versa. We conclude by noting that significant sex and ethnic differences exist but that future studies are needed to more fully explicate how they may moderate the associations between stress and aging.