Social Networks and Cerebrospinal Fluid Biomarkers of Alzheimer's Disease Pathology in Cognitively Intact Older Adults: The CABLE Study

Hearing impairment is associated with cognitive decline, brain atrophy and tau pathology

BACKGROUND

Hearing impairment was recently identified as the most prominent risk factor for dementia. However, the mechanisms underlying the link between hearing impairment and dementia are still unclear.

METHODS

We investigated the association of hearing performance with cognitive function, brain structure and cerebrospinal fluid (CSF) proteins in cross-sectional, longitudinal, mediation and genetic association analyses across the UK Biobank (N = 165,550), the Chinese Alzheimer's Biomarker and Lifestyle (CABLE, N = 863) study, and the Alzheimer's Disease Neuroimaging Initiative (ADNI, N = 1770) database.

FINDINGS

Poor hearing performance was associated with worse cognitive function in the UK Biobank and in the CABLE study. Hearing impairment was significantly related to lower volume of temporal cortex, hippocampus, inferior parietal lobe, precuneus, etc., and to lower integrity of white matter (WM) tracts. Furthermore, a higher polygenic risk score (PRS) for hearing impairment was strongly associated with lower cognitive function, lower volume of gray matter, and lower integrity of WM tracts. Moreover, hearing impairment was correlated with a high level of CSF tau protein in the CABLE study and in the ADNI database. Finally, mediation analyses showed that brain atrophy and tau pathology partly mediated the association between hearing impairment and cognitive decline.

INTERPRETATION

Hearing impairment is associated with cognitive decline, brain atrophy and tau pathology, and hearing impairment may reflect the risk for cognitive decline and dementia as it is related to bran atrophy and tau accumulation in brain. However, it is necessary to assess the mechanism in future animal studies.

FUNDING

A full list of funding bodies that supported this study can be found in the Acknowledgements section.

The effects of loneliness, social isolation, and associated gender differences on the risk of developing cognitive impairment for Chinese oldest old

OBJECTIVES

To investigate whether loneliness and social isolation could independently predict subsequent risk of cognitive impairment in Chinese oldest old, and to examine possible gender differences.

METHODS

The sample included 2,732 older adults aged 80 years and above with intact cognitive function from the Chinese Longitudinal Healthy Longevity Survey 2002-2018 waves, with an average follow-up of 4.24 years. Loneliness was measured by a single-item question about how often the participant felt lonely. Social isolation was defined by marital status, frequent visits by family members, and social activity engagement. Cognitive impairment was defined based on Mini-Mental State Examination scores.

RESULTS

Cox regression showed that social isolation independently predicted a higher risk of developing cognitive impairment at follow-up (HR = 1.14, 95% CI [1.03, 1.27], p = 0.014). Importantly, although there was no main effect of loneliness, a significant interaction between gender and loneliness (p = 0.013) suggested that increased loneliness was associated with a higher risk of developing cognitive impairment for men but not for women.

CONCLUSION

To prevent cognitive impairment and promote healthy longevity, socially isolated adults in their oldest old age should receive more attention, and men who often feel lonely should be offered with more emotional support.

Plasma Exo-miRNAs Correlated with AD-Related Factors of Chinese Individuals Involved in Aβ Accumulation and Cognition Decline

Numerous studies have investigated the risk factors of Alzheimer’s disease (AD); however, AD-risk factors related miRNAs were rarely reported. In this study, AD-risk factor related miRNAs of 105 Chinese individuals (45 AD patients and 60 cognitively normal controls) were investigated. The results showed that Hsa-miR-185-5p, Hsa-miR-20a-5p, and Hsa-miR-497-5p were related to AD and education, Hsa-miR-185-5p, Hsa-miR-181c-5p, Hsa-miR-664a-3p, Hsa-miR-27a-3p, Hsa-miR-451a, and Hsa-miR-320a were related to AD and depression. Target prediction of above miRNAs showed that these miRNAs were involved in the generation and clearance of amyloid-beta (Aβ), important molecules related to cognition, and disease-activated microglia response to AD. It is worth noting that Hsa-miR-185-5p was related to both education and depression, whose decreased expression pattern in AD patients was alleviated by education and enhanced by depression, and participates in Aβ generation and accumulation. Our results indicated that certain education and depression factors can contribute to AD progression by modulating miRNA expression, implying that preventive interventions might alter AD progression in Chinese patients.

The Relationship Between Suboptimal Social Networks and Postoperative Delirium: The PNDABLE Study

Background

Although it has been proven that social networks are related to cognition, studies are conducted to characterize the correlation between social networks and postoperative delirium (POD).

Objective

We investigated whether suboptimal social networks are a risk factor for POD, and to verify whether different levels of intimacy in the same social relationship can affect the concentration of cerebrospinal fluid (CSF) biomarkers, such as amyloid-β (Aβ42), total tau (T-tau), and phosphorylated tau (P-tau), and the mediating role of CSF biomarkers between social network and POD in middle-aged and elderly Han people.

Methods

Our study recruited 743 participants from The Perioperative Neurocognitive Disorder and Biomarker Lifestyle (PNDABLE) study. Confusion Assessment Method (CAM) was used to evaluate the incidence of POD and its severity was measured using the Memorial Delirium Assessment Scale (MDAS). The social networks were measured using self-reported questionnaires about social ties. Mann–Whitney U test, Logistic Regression and Independent-samples test were used for Statistical Analysis.

Results

The incidence of POD was 20.7%. Mann–Whitney U test showed that the total score of the social network was associated with POD (P < 0.001). Independent-samples test showed that different levels of intimacy in the same social relationship were significantly associated with CSF POD biomarkers, and mediation analyses revealed that the association between suboptimal social networks and POD was partially mediated by T-tau (proportion: 20%), P-tau (proportion: 33%), Aβ42/T-tau (proportion: 14%), and Aβ42/P-tau (proportion: 15%).

Conclusion

Having suboptimal social networks is a risk factor for POD in middle-aged and elderly Han people. CSF POD biomarkers can mediate the correlation between suboptimal social networks and POD, which is mainly mediated by tau protein.

Clinical Trial Registration

www.chictr.org.cn, identifier ChiCTR2000033439.

Social health, social reserve and dementia

PURPOSE OF REVIEW

There is increasing recognition of social health being protective against disease, including age-related cognitive decline and dementia. Many concepts around social health, reserve and connectedness are imprecise and without agreed definitions. The mechanisms by which social health is protective are not well understood.

RECENT FINDINGS

Several observational studies suggest that social participation and connectedness are protective against cognitive decline whereas loneliness is a risk factor for dementia. The possible mechanisms include effects on inflammatory process and immune function, reduced vascular disease risk, improved health behaviours, lower risk of depression, and increased cognitive reserve through cognitive stimulation and physical activity. Social networks have been shown to modify the relationship between Alzheimer's disease and cognitive impairment. The relationship of social networks is, however, reciprocal, with dementia leading to social loss, which in turn worsens cognitive decline. Social reserve is conceptualized as both brain processes underlying the ability and predisposition to form meaningful social ties, and their instantiation as an environmental resource in high-quality social networks.

SUMMARY

Consistent definitions of social health-related terms will lead to better understanding of their determinants so that tailored interventions can be developed to increase social reserve and improve social health of an individual.