Progression of socio-cognitive impairment from healthy aging to Alzheimer's Dementia: A systematic Review and Meta-Analysis

Association between midday napping and long-term trajectories of cognitive function among middle-aged and older Chinese adults

BACKGROUND

The prevalence of dementia has become an increasingly important public health priority. This study investigated the association between midday napping and long-term trajectories of cognitive function in middle-aged and older Chinese adults.

METHODS

Among 4648 participants aged 45+ years extracted from the China Health and Retirement Longitudinal Study (CHARLS). The components of the Telephone Interview of Cognitive Status battery (TICS-10) was used to assess cognitive function. Group-based trajectory modelling (GBTM) was used to identify long-term trajectories of cognitive function. Multinomial logistic regression model was used to estimate risk ratios (RRs) and 95% confidence intervals (CIs).

RESULTS

Three distinct long-term trajectories of cognitive function reflected patterns of rapid decline, slow decline, and stable. The RR (95% CI) for rapid decline was 1.45 (1.05-2.01) for 0 minutes, 1.49 (1.05-2.12) for 31-90 minutes, and 2.19 (1.41-3.42) for >90 minutes compared with midday napping 1-30 minutes. The RR (95% CI) for slow decline was 1.22 (1.02-1.47) for 0 minutes, 1.27 (1.04-1.55) for 31-90 minutes, and 1.80 (1.38-2.35) for >90 minutes compared with midday napping 1-30 minutes. In addition, the increased risk of cognitive decline that transferred from >90 to 31-90 minutes, switched from 31-90 to >90 minutes, and persisted in >90 minutes compared with midday napping 1-30 minutes, especially rapid decline.

CONCLUSIONS

There was a longitudinal association between no and long (>30 minutes) midday napping and long-term trajectories of cognitive decline, especially rapid decline. The study is a 4-year observational in nature and provides limited evidence for establishing causal relationships.

Intact embodiment during perspective-taking in older adults is not affected by focal tDCS

Embodied processing is crucial for visual perspective taking (VPT), with evidence from non-invasive transcranial direct current stimulation (tDCS) suggesting a causal role of the right temporoparietal junction (rTPJ). However, it is not known whether such embodied factors are maintained in older adults or whether rTPJ-tDCS has comparable effects in advanced age. We employed a balanced and sham-tDCS controlled, double-blinded, cross-over design, including two randomized experimental groups of healthy older adults, receiving focal tDCS over either the rTPJ (n = 30), or a control region in the dorsomedial prefrontal cortex (dmPFC, n = 30). A healthy young control group (n = 30, not receiving tDCS) was included to investigate potential changes in embodied processing in older adults. All groups completed neuropsychological baseline testing and an experimental VPT paradigm, in which perspective-taking (requiring embodied rotation) and perspective-tracking (line-of-sight judgements) were assessed. Structural magnetic resonance imaging data were acquired to conduct individualized current flow simulations, aimed at identifying potential changes in neurophysiological effects of tDCS in older adults. Older adults responded slower across perspective tracking and perspective taking tasks but showed comparable embodied effects of body posture and angle of rotation during perspective taking. Contrary to previous results in younger adults that demonstrated regionally and task-specific effects of focal rTPJ-tDCS, no stimulation effects on embodied processing were found in older adults. Electrical field simulations suggested focal current delivery in both age-groups but also significantly reduced current strength in the target regions for tDCS in older adults. Older adults are as embodied as young adults during perspective taking. However, tDCS administered to the rTPJ or dmPFC had no effect, which may be explained by reduced current delivery to the target regions due to age-associated changes in skull and brain anatomy and/or functional brain reorganization. Our results are in line with previous studies suggesting that tDCS effects obtained in young participants may not translate directly to advanced age. Future studies could address this by using individualized modelling approaches aimed at adjusting current dose for (older) study participants and pre-stimulation functional imaging involving VPT tasks-of-interest, to identify optimized target regions for tDCS.Registration: ClinicalTrials.gov Identifier: NCT04633499.

Emotion regulation in people living with dementia and their spouses: the role of neuropsychiatric symptoms

OBJECTIVES

People with dementia (PwD) and their care partners (CP) may have difficulties in emotion regulation, and individual differences in emotion regulation may be related to PwD's neuropsychiatric symptoms. This study explores whether there is self-awareness of PwD's difficulties in emotion regulation and whether CP's emotion regulation relates to the PwD's neuropsychiatric symptoms, potentially revealing bias or interpersonal effects.

METHOD

We used data from the Wish Outcome Obstacle Plan Study with a sample of 45 PwD and their spousal CP (n = 90 individuals). Multivariate linear regression models were used to investigate the associations between the CP-reported neuropsychiatric symptoms in PwD and self-reports of emotion regulation in both dyad members, net of sociodemographic and health factors. Separate analyses were conducted for each neuropsychiatric subsyndrome and each domain of difficulties in emotion regulation.

RESULTS

Increasing severity of neuropsychiatric symptoms was associated with higher difficulties in emotion regulation in PwD (ß = 1.23, p < 0.05), but not with CP's difficulties in emotion regulation. When CP reported more severe neuropsychiatric symptoms in PwD, PwD reported that they had difficulties in accepting emotions, controlling impulses, goal-directed behaviors, and accessing emotion regulation strategies, but not in emotion awareness and clarification. Proxy-reports of hyperactivity and psychosis subsyndromes are significantly related to PwD's self-reported difficulties in emotion regulation.

CONCLUSION

PwD reported difficulties in emotion regulation at the early stage of dementia. Proxy-reported neuropsychiatric symptoms may capture PwD's emotion regulation capability and not be biased by CP's difficulties in emotion regulation.

APOE genotype, hippocampal volume, and cognitive reserve predict improvement by cognitive training in older adults without dementia: a randomized controlled trial

Cognitive training (CT) programs aim to improve cognitive performance and impede its decline. Thus, defining the characteristics of individuals who can benefit from these interventions is essential. Our objectives were to assess if the cognitive reserve (CR), APOE genotype (e4 carriers/non-carriers) and/or hippocampal volume might predict the effectiveness of a CT program. Participants were older adults without dementia (n = 226), randomized into parallel experimental and control groups. The assessment consisted of a neuropsychological protocol and additional data regarding total intracranial, gray matter, left/right hippocampus volume; APOE genotype; and Cognitive Reserve (CR). The intervention involved multifactorial CT (30 sessions, 90 min each), with an evaluation pre- and post-training (at six months); the control group simply following the center's routine activities. The primary outcome measures were the change in cognitive performance and the predictors of change. The results show that APOE-e4 non-carriers (79.1%) with a larger left hippocampal volume achieved better gains in semantic verbal fluency (R2 = .19). Subjects with a larger CR and a greater gray matter volume better improved their processing speed (R2 = .18). Age was correlated with the improvement in executive functions, such that older age predicts less improvement (R2 = .07). Subjects with a larger left hippocampal volume achieved more significant gains in general cognitive performance (R2 = .087). In conclusion, besides the program itself, the effectiveness of CT depends on age, biological factors like genotype and brain volume, and CR. Thus, to achieve better results through a CT, it is essential to consider the different characteristics of the participants, including genetic factors.Trial registration: Trial retrospectively registered on January 29th, 2020-(ClinicalTrials.gov -NCT04245579).

How interpersonal distance varies throughout the lifespan

Interpersonal Distance (IPD) is defined as the physical distance that individuals maintain between themselves and others during social interactions. While literature has extensively focused on this everyday social behavior, how IPD changes throughout the lifespan remains an open question. In this study, 864 participants, aged 3-89 years, performed the Stop Distance Paradigm in their real-life environments, and we measured the distance they kept from both familiar and unfamiliar others during social interactions. We found that IPD not only differs based on the identity of the other person (familiar versus unfamiliar) but critically declines as a function of age, following two distinct non-linear trends for familiar and unfamiliar others. Moreover, behavioral variability also undergoes a lifetime development, with IPD becoming more stable as age increases. Overall, the present study suggests that IPD is a complex and acquired behavior that changes throughout the lifespan and varies according to individual and situational variables.

Improving mentalizing deficits in older age with region-specific transcranial direct current stimulation

Older adults have difficulties to detect the intentions, thoughts, and feelings of others, indicating an age-associated decline of socio-cognitive abilities that are known as "mentalizing". These deficits in mental state recognition are driven by neurofunctional alterations in brain regions that are implicated in mentalizing, such as the right temporo-parietal junction (rTPJ) and the dorso-medial prefrontal cortex (dmPFC). We tested whether focal transcranial current stimulation (tDCS) of the rTPJ and dmPFC has the potential to eliminate mentalizing deficits in older adults. Mentalizing deficits were assessed with a novel mindreading task that required the recognition of mental states in child faces. Older adults (n = 60) performed worse than younger adults (n = 30) on the mindreading task, indicating age-dependent deficits in mental state recognition. These mentalizing deficits were ameliorated in older adults who received sham-controlled andodal tDCS over the rTPJ (n = 30) but remained unchanged in older adults who received sham-controlled andodal tDCS over the dmPFC (n = 30). We, thus, showed for the first time that anodal tDCS over the rTPJ has the potential to remediate age-dependent mentalizing deficits in a region-specific way. This provides a rationale for exploring stimulation-based interventions targeting mentalizing deficits in older age.

Multidimensional assessment of social cognition using non-immersive virtual reality in dementia with Lewy bodies and Alzheimer's disease: an exploratory study

INTRODUCTION

Few studies have focused on social cognition in dementia with Lewy bodies (DLB), even though some brain structures being well known as underlying social cognitive processes are directly impacted in this disease. Furthermore, social cognition processes have been mostly studied independently using evaluations with poor ecological validity. We aimed at studying the ability of a new naturalistic and multidimensional social cognition task to reveal impairments in DLB patients. We chose to compare the profile of these patients with that of Alzheimer's disease (AD) patients, for which social cognition is better preserved.

METHOD

Fifteen patients (DLB: n = 7; AD: n = 8) and 28 healthy controls underwent the REALSoCog task. They encountered several social situations (e.g. control versus transgressions) in a non-immersive virtual city environment allowing the assessment of moral cognition, cognitive and affective theory of mind (ToM), emotional empathy and behavioral intentions.

RESULTS

The main results showed (i) a lower ability to detect transgressions in DLB patients, particularly conventional ones, whereas moral cognition seemed better preserved in AD patients; (ii) a cognitive ToM impairment in both DLB and AD patients, while affective ToM is impaired only in DLB patients; (iii) a decreased emotional empathy specifically observed in DLB patients; (iv) more inappropriate behavioral intentions, mainly in DLB patients, but also in some AD patients.

CONCLUSIONS

This study suggests the feasibility and potential interest of the REALSoCog task in revealing social cognition deficits, particularly for DLB patients by showing different social patterns as compared to AD patients. These results offer interesting clinical perspectives to develop more naturalistic tasks in such populations and for clinical differential diagnosis. Limitations and future perspectives are discussed.

Dynamic and/or multimodal assessments for social cognition in neuropsychology: Results from a systematic literature review

Objective: Despite the prevalence of socio-cognitive disturbances, and their important diagnostic/therapeutic implications, the assessment of these disturbances remains scarce. This systematic review aims to identify available social cognition tools for adult assessment that use multimodal and/or dynamic social cues, specifying their strengths and limitations (e.g. from a methodological, psychometric, ecological, and clinical perspective). Method: An electronic search was conducted in Pubmed, PsychINFO, Embase and Scopus databases for articles published up to the 3th of January 2023 and the first 200 Google Scholar results on the same date. The PRISMA methodology was applied, 3884 studies were screened based on title and abstract and 329 full texts were screened. Articles using pseudo-dynamic methodologies (e.g. morphing), reported only subjective or self-reported measures, or investigated only physiological or brain activity responses were excluded. Results: In total, 149 works were included in this review, representing 65 assessment tools (i.e. 48% studying emotion recognition (n = 31), 32% Theory of Mind (n = 21), 5% empathy (n = 3), 1.5% moral cognition/social reasoning (n = 1), and 14% being multimodal (n = 9)). For each study, the tool's main characteristics, psychometric properties, ecological validity indicators and available norms are reported. The tools are presented according to social-cognitive process assessed and communication channels used. Conclusions: This study highlights the lack of validated and standardized tools. A few tools appear to partially meet some clinical needs. The development of methodologies using a first-person paradigm and taking into account the multidimensional nature of social cognition seems a relevant research endeavour for greater ecological validity.

Relationship between neuroimaging and emotion recognition in mild cognitive impairment patients

OBJECTIVE

Dementia is a major public health problem with high needs for early detection, efficient treatment, and prognosis evaluation. Social cognition impairment could be an early dementia indicator and can be assessed with emotion recognition evaluation tests. The purpose of this study is to investigate the link between different brain imaging modalities and cognitive status in Mild Cognitive Impairment (MCI) patients, with the goal of uncovering potential physiopathological mechanisms based on social cognition performance.

METHODS

The relationship between the Reading the Mind in the Eyes Test (RMET) and some clinical and biochemical variables ([18 F]FDG PET-CT and anatomical MR parameters, neuropsychological evaluation, and CSF biomarkers) was studied in 166 patients with MCI by using a correlational approach.

RESULTS

The RMET correlated with neuropsychological variables, as well as with structural and functional brain parameters obtained from the MR and FDG-PET imaging evaluation. However, significant correlations between the RMET and CSF biomarkers were not found.

DISCUSSION

Different neuroimaging parameters were found to be related to an emotion recognition task in MCI. This analysis identified potential minimally-invasive biomarkers providing some knowledge about the physiopathological mechanisms in MCI.

Neural correlates of empathy in mild cognitive impairment

The occurrence of clinically significant changes in empathy is a matter of debate in Alzheimer's disease (AD). Altered empathic mechanisms observed in AD may be a consequence of cognitive impairment, more specifically of reduced mental flexibility and self-regulation. The present study explored possible changes in empathy for subjects in the prodromal phase of AD, namely mild cognitive impairment (MCI) due to AD, and of their neural substrates. Eighteen MCI patients and 20 healthy controls (HC) were included in the study. The Interpersonal Reactivity Index (IRI) questionnaire was administered to each participant. The IRI encompasses four factors: Perspective Taking; Fantasy; Empathic Concern; Personal Distress. MCI patients underwent a magnetic resonance imaging structural examination and were compared to 30 healthy controls (HC-MRI). A limited number of cortical and subcortical regions involved in social cognition was selected as regions of interest (ROIs). MCI individuals obtained lower scores than HC in the Perspective Taking and Fantasy subscales of the IRI, whereas they obtained higher scores on Empathic Concern. Regarding neuroimaging data, a significant correlation emerged between IRI scores and the neural measurements of different regions involved in empathy, especially covering the temporoparietal junction, which is a critical region engaged in both affective and cognitive dimensions of empathy. The results of the present study suggest that a subtle impairment in regulatory mechanisms of empathy may occur very early during the course of AD, possibly as a consequence of neuropathological changes occurring in brain regions involved in social cognition.

Theory of Mind and Executive Functions in Individuals with Mild Cognitive Impairment or Healthy Aging

Social cognition involves skills for maintaining harmonious personal and social relationships throughout life. Social cognition issues, including Theory of Mind (ToM), can significantly impact the well-being of older individuals and intensify with the onset of neurological conditions. Mild Cognitive Impairment (MCI) is a state between healthy and pathological neurocognitive aging, where monitoring social functions is crucial. Despite numerous studies on ToM challenges in older adults and cognitive disorders, the underlying mechanisms remain debated. Uncertainty exists regarding whether ToM deficits are related to other cognitive functions, such as Executive Functions (EFs). Our study examined the correlation between EF and ToM performance in 32 MCI patients and 36 healthy elderly controls. The findings revealed a link between EF and ToM performance among healthy elderly individuals. Specifically, within the assessed EFs, the role of the working memory (WM) emerged. The study also highlighted distinctions between the MCI group and the healthy elderly group, showing that despite a general reduction in cognitive performance, the condition could impact these abilities in different ways. The study contributes to the literature, fostering comprehension of the mechanisms underlying ToM difficulties, while also paving the way for targeted interventions and enhanced clinical or preventative care.

Neural bases of loss aversion when choosing for oneself versus known or unknown others

Despite the ubiquitous interdependence between one's own decisions and others' welfare, and the controversial evidence on the behavioral effect of choosing for others, the neural bases of making decisions for another versus oneself remain unexplored. We investigated whether loss aversion (LA; the tendency to avoid losses over approaching equivalent gains) is modulated by (i) choosing for oneself, other individuals, or both; (ii) knowing or not knowing the other recipients; or (iii) an interaction between these factors. We used fMRI to assess the brain activations associated with choosing whether to accept or reject mixed gambles, either for oneself, for another player, or both, in 2 groups of 28 participants who had or had not briefly interacted with the other players before scanning. Participants displayed higher LA for choices involving their payoff compared with those affecting only the payoff of other, known, players. This "social" modulation of decision-making was found to engage the dorsomedial prefrontal cortex and its inhibitory connectivity to the middle cingulate cortex. This pattern might underpin decision-making for known others via self-other distinction processes associated with dorsomedial prefrontal areas, with this in turn promoting the inhibition of socially oriented responses through the downregulation of the midcingulate node of the empathy network.

Emotion recognition and baseline cortisol levels relationship in early Alzheimer disease

BACKGROUND

Emotion recognition is often impaired in early Alzheimer's disease (AD) and can be evaluated using the Reading the Mind in the Eyes Test (RMET). Similarly, cortisol levels can affect cognition and could be considered a biomarker of AD.

OBJECTIVES

The aim of this study was to analyse the relationship between the emotion recognition task and cortisol levels in participants with early Alzheimer Disease (AD).

METHODS

Complex emotion recognition was assessed with RMET, and plasma cortisol levels were determined by mass spectrometry in participants classified into mild cognitive impairment (MCI) due to AD (n = 25), mild dementia (MD) due to AD (n = 20), MCI non-AD (n = 34), MD non-AD (n = 13) and healthy controls (HC) (n = 16) groups.

RESULTS

Significantly lower positive emotion recognition was found in the MCI non-AD group (p = 0.02) and lower emotion recognition in MD (AD and non-AD) groups (p < 0.01) compared to the healthy group. In addition, significant differences were observed between cortisol and all RMET scores among the MCI and MD groups (p < 0.01). A significant correlation was also obtained between total and neutral RMET scores and cortisol levels in MD groups (p = 0.01).

CONCLUSIONS

These outcomes suggest that detection of positive emotion dysfunction could help to identify MCI non-AD patients. Furthermore, general impaired emotion recognition and high cortisol levels may be associated with cognitive impairment at mild dementia level.

Heart failure decouples the precuneus in interaction with social cognition and executive functions

Aging increases the risk to develop Alzheimer's disease. Cardiovascular diseases might accelerate this process. Our study aimed at investigating the impact of heart failure on brain connectivity using functional magnetic resonance imaging at resting state. Here we show brain connectivity alterations related to heart failure and cognitive performance. Heart failure decreases brain connectivity in the precuneus. Precuneus dysconnectivity was associated with biomarkers of heart failure-left ventricular ejection fraction and N-terminal prohormone of brain natriuretic peptide-and cognitive performance, predominantly executive function. Meta-analytical data-mining approaches-conducted in the BrainMap and Neurosynth databases-revealed that social and executive cognitive functions are mainly associated with those neural networks. Remarkably, the precuneus, as identified in our study in a mid-life cohort, represents one central functional hub affected by Alzheimer's disease. A long-term follow-up investigation in our cohort after approximately nine years revealed more severe cognitive impairment in the group with heart failure than controls, where social cognition was the cognitive domain mainly affected, and not memory such as in Alzheimer's disease. In sum, our results indicate consistently an association between heart failure and decoupling of the precuneus from other brain regions being associated with social and executive functions. Further longitudinal studies are warranted elucidating etiopathological mechanisms.

β-Hydroxybutyrate Regulates Activated Microglia to Alleviate Neurodegenerative Processes in Neurological Diseases: A Scoping Review

This scoping review aimed to summarise the effects of the ketone body β-hydroxybutyrate. The review details the revealed pathways and functional properties following its intervention in the context of neurodegenerative diseases. In this study, 5 research publications that met the inclusion and exclusion criteria were shortlisted. Following the intervention, we discovered a tendency of reduced inflammatory status in microglia, as evidenced by lower levels of pro-inflammatory mediators produced, reduced microgliosis in afflicted tissues, and enhanced cognitive functions in neurodegenerative models. We found that there is a significant overlap in the mechanism of action of β-hydroxybutyrate (BHB) via activation of the G-protein-Coupled Receptor 109A (GPR109a) receptor and deactivation of the inflammasome complex. Furthermore, although comparing outcomes can be challenging due to the heterogeneity in the study model, the results we have assembled here were consistent, giving us confidence in the intervention's efficacy. We also discussed new studies where BHB is involved in various roles in regulating inflammation in microglia, allowing for fresh therapeutic targets against neurodegeneration. This brief review provides evidence to support the huge potential of BHB in the treatment of neurodegenerative illnesses.