A Prospective Sociocentric Study of 2 Entire Traditional Korean Villages: The Korean Social Life, Health, and Aging Project (KSHAP).

The Korean Social Life, Health, and Aging Project (KSHAP) was a multidisciplinary prospective study conducted in South Korea that measured various health biomarkers from blood, hair, and brain magnetic resonance imaging, and we examined their associations with sociocentric (global) social network data of older adults in 2 entire villages (or cohorts). Cohort K included participants aged 60 years or older, and cohort L included participants aged 65 years or older. We performed a baseline survey involving 814 of the 860 individuals (94.7% response rate) in cohort K in 2012 and 947 of the 1,043 individuals (90.8% response rate) in cohort L in 2017. We gathered longitudinal data for 5 waves in cohort K from 2011 to 2019 and 2 waves in cohort L from 2017 to 2022. Here, we describe for the first time the follow-up design of the KSHAP, the changes in social networks, and various biomarkers over a number of years. The data for cohort K are publicly available via the Korean Social Science Data Archive as well as the project website, and the data for cohort L will be shared soon.

Association between Loneliness and Memory Function through White Matter Hyperintensities in Older Adults: The Moderating Role of Gender.

Loneliness has an important impact on memory function in late life. However, the neural mechanism by which loneliness detrimentally influences memory function remains elusive. Furthermore, it remains unclear whether the association between loneliness and memory function varies by gender. The current study aimed to investigate the neural mechanism underlying the association between loneliness and episodic memory function and explore whether it varies with gender among cognitively normal older adults. A total of 173 community-dwelling adults aged 60 years or older from the Korean Social Life, Health, and Aging Project (KSHAP) study (mean age = 71.87) underwent an assessment of loneliness, neuropsychological testing, and structural magnetic resonance imaging. The association between loneliness and episodic memory function was mediated by the volume of white matter hyperintensities (WMHs), but not by hippocampal or gray matter volumes. In addition, the association between loneliness and memory function through WMHs was significantly moderated by gender; specifically, the indirect effect was significant among men but not among women. The study suggests that WMHs may be a potential neurological mechanism that causes late-life memory dysfunction associated with loneliness in older men. The findings underscore the need for gender-specific interventions to mitigate memory impairment associated with late-life loneliness, with significant public health implications.

Social network position and the Conserved Transcriptional Response to Adversity in older Koreans.

BACKGROUND: Social connections are crucial to human health and well-being. Previous research on molecular mechanisms in health has focused primarily on the individual-level perception of social connections (e.g., loneliness). This study adopted socio-centric social network analysis that includes all social ties from the entire population of interest to examine the group-level social connections and their association with a molecular genomic measure of health. METHODS: Using socio-centric (global) social network data from an entire village in Korea, we investigated how social network characteristics are related to immune cell gene expression among older adults. Blood samples were collected (N = 53, 65-79 years) and mixed effect linear model analyses were performed to examine the association between social network characteristics and Conserved Transcriptional Response to Adversity (CTRA) RNA expression patterns. RESULTS: Social network positions measured by k-core score, the degree of cohesive core positions in an entire village, were significantly associated with CTRA downregulation. Such associations emerged above and beyond the effects of perceived social isolation (loneliness) and biobehavioral risk factors (smoking, alcohol, BMI, etc.). Social network size, defined as degree centrality, was also associated with reduced CTRA gene expression, but its association mimicked that of perceived social isolation (loneliness). CONCLUSIONS: The current findings implicate community-level social network characteristics in the regulation of individual human genome function above and beyond individual-level perceptions of connectedness.

Brain connectivity during social exclusion differs depending on the closeness within a triad among older adults living in a village.

Social exclusion occurs in various types of social relationships, from anonymous others to close friends. However, the role that social relationships play in social exclusion is less well known because most paradigms investigating social exclusion have been done in laboratory contexts, without considering the features of individuals' real-world social relationships. Here, we addressed this gap by examining how pre-existing social relationships with rejecters may influence the brain response of individuals experiencing social exclusion. Eighty-eight older adults living in a rural village visited the laboratory with two other participants living in the same village and played Cyberball in an Magnetic Resonance Imaging scanner. Utilizing whole-brain connectome-based predictive modeling, we analyzed functional connectivity (FC) data obtained during the social exclusion task. First, we found that the level of self-reported distress during social exclusion was significantly related to sparsity, i.e. lack of closeness, within a triad. Furthermore, the sparsity was significantly predicted by the FC model, demonstrating that a sparse triadic relationship was associated with stronger connectivity patterns in brain regions previously implicated in social pain and mentalizing during Cyberball. These findings extend our understanding of how real-world social intimacy and relationships with excluders affect neural and emotional responses to social exclusion.

Association of group-level segregation with cardiovascular health in older adults: an analysis of data from the Korean Social Life, Health, and Aging Project.

OBJECTIVES: The adverse health effects of individual-level social isolation (e.g., perceived loneliness) have been well documented in older adults. However, little is known about the impact of collective-level social isolation on health outcomes. We sought to examine the association of group-level segregation with cardiovascular health (CVH) in older adults. METHODS: From the prospective Korean Social Life, Health, and Aging Project database, we identified 528 community-dwelling older adults who were aged ≥60 years or were married to those aged ≥60 years. Participants who belonged to smaller social groups separate from the major social group were defined as group-level-segregated. The CVH score was calculated as the number of ideal non-dietary CVH metrics (0-6), as modified from the American Heart Association's Life's Simple 7. Using ordinal logistic regression models, we assessed cross-sectional and longitudinal associations between group-level segregation and CVH. RESULTS: Of the 528 participants (mean age, 71.7 years; 60.0% female), 108 (20.5%) were segregated at baseline. In the crosssectional analysis, group-level segregation was significantly associated with lower odds of having a higher CVH score at baseline after adjusting for socio-demographic factors and cognitive function (odds ratio [OR], 0.64; 95% confidence interval [CI], 0.43 to 0.95). Among 274 participants who completed an 8-year follow-up, group-level segregation at baseline was marginally associated with lower odds of having a higher CVH score at 8 years (OR, 0.49; 95% CI, 0.24 to 1.02). CONCLUSIONS: Group-level segregation was associated with worse CVH. These findings imply that the social network structure of a community may influence its members' health status.

The Effect of Cognitive Impairment on the Association Between Social Network Properties and Mortality Among Older Korean Adults.

OBJECTIVES: This study investigated the effect of cognitive impairment on the association between social network properties and mortality among older Korean adults. METHODS: This study used data from the Korean Social Life, Health, and Aging Project. It obtained 814 older adults' complete network maps across an entire village in 2011-2012. Participants' deaths until December 31, 2020 were confirmed by cause-of-death statistics. A Cox proportional hazards model was used to assess the risks of poor social network properties (low degree centrality, perceived loneliness, social non-participation, group-level segregation, and lack of support) on mortality according to cognitive impairment. RESULTS: In total, 675 participants (5510.4 person-years) were analyzed, excluding those with missing data and those whose deaths could not be verified. Along with cognitive impairment, all social network properties except loneliness were independently associated with mortality. When stratified by cognitive function, some variables indicating poor social relations had higher risks among older adults with cognitive impairment, with adjusted hazard ratios (HRs) of 2.12 (95% confidence interval [CI], 1.34 to 3.35) for social nonparticipation, 1.58 (95% CI, 0.94 to 2.65) for group-level segregation, and 3.44 (95% CI, 1.55 to 7.60) for lack of support. On the contrary, these effects were not observed among those with normal cognition, with adjusted HRs of 0.73 (95% CI, 0.31 to 1.71), 0.96 (95% CI, 0.42 to 2.21), and 0.95 (95% CI, 0.23 to 3.96), respectively. CONCLUSIONS: The effect of social network properties was more critical among the elderly with cognitive impairment. Older adults with poor cognitive function are particularly encouraged to participate in social activities to reduce the risk of mortality.

Psychological well-being and salivary markers of inflammation: The moderating effect of age.

Increasing evidence suggests a significant impact of higher psychological well-being (PWB) on health outcomes; however, such associations have been studied exclusively in middle-aged to older adults. This study examined the aging effect on PWB measures as well as the moderating effect of age on the link between PWB and inflammation, using salivary markers by comparing the younger adults (n = 127; Mage = 22.98 years) versus older adults (n = 75; Mage = 75.60 years). Older adults showed significantly lower levels of PWB, particularly regarding purpose in life and personal growth. Moreover, higher purpose in life was associated with lower salivary IL-1ß and IL-6 (b = 0.83, p < .001; b = 0.81, p < .01) only in the older adult group but not in younger adults. These findings highlight the potential buffering effect of the sense of living well on physiological pathways in later life.

Association of social network properties with resilience and depression among community-based Korean population.

We aimed to determine how the properties of social networks relate to resilient-related status. This cross-sectional study used baseline data from the Cardiovascular and Metabolic Disease Etiology Research Center cohort and included 11,132 participants. Ego-centric social network size and intimacy were used to reflect social network properties. Resilient-related status was operationally defined based on the participant's response to the Life Experience Survey and the Back Depression Inventory Ⅱ. Participants were categorized into three groups: reference (no negative life event; no depression), resilient (with negative life event; but no depression), and depression (no/with negative life event; with depression). Multinomial logistic regression models were used to estimate the association of social networks on the resilient-related status after adjusting for all covariates. Social network size was positively associated with the resilient group for both sex (male: OR = 1.01 [95% CI = 0.96 to 1.05], female: OR = 1.07 [95% CI = 1.03 to 1.11]), whereas intimacy showed a negative association (male: OR = 0.91 [95% CI = 0.82 to 1.01], female: OR = 0.84 [95% CI = 0.76 to 0.92]). Additionally, as each social network property increased, the likelihood of being categorized as belonging to the depression group decreased, regardless of age and sex.

Association Between Social Network and Cognitive Function: A Cross-Sectional Assessment From the Cardiovascular and Metabolic Diseases Etiology Research Center Cohort (2013-2018).

Background: This study aimed to investigate how social networks are associated with cognitive function in the middle-aged and elderly Korean population. Methods: A total of 7,704 individuals over the age of 50 were included from the baseline recruitment of the Cardiovascular and Metabolic Diseases Etiology Research Center cohort from the years 2013 to 2018. Egocentric social network characteristics including network size, intimacy, and frequency of face-to-face meetings were measured as exposures, and the Korean version of Mini-Mental State Examination (K-MMSE) score was measured to reflect general cognitive function as an outcome. We also stratified the analysis by income level into tertiles, with income caps of 42,000 thousand won and 72,000 thousand won. A general linear regression model was used, adjusting for age, gender, socioeconomic factors, lifestyle factors, depressive symptoms, and study settings. Results: Social network properties were positively associated with cognitive function in both men and women. However, the specific estimates varied according to gender and income level. In men, frequency was most significantly associated with cognitive function (standardized ß = 0.093, p-value <0 .0001). In women, the strength of the association with cognitive function was found in size (standardized ß = 0.055, p-value = 0.001). The effect modification of income level could be seen in the association between frequency and cognitive function. The strongest association between frequency and cognitive function was found in the middle income group in men (standardized ß = 0.114, p-value = 0.0063), and the low income group in women (standardized ß = 0.076, p-value = 0.0039). Conclusion: There were positive associations between social network properties (i.e., size, intimacy, and frequency of face-to-face meetings) and cognitive function. The degree of association varied according to social network properties, gender, and income level. Overall, among social network properties, social network size was an important factor in the cognition of women, whereas frequency was important in the cognition of men.

Social Network Characteristics Predict Loneliness in Older Adults.

INTRODUCTION: Social isolation is detrimental to late-life health outcomes. Although objective social isolation is a major source of perceived loneliness, how different layers of social disconnection systematically constitute the subjective experience of loneliness remains unclear. METHODS: This study focused on older adults who participated in the Korean Social Life, Health, and Aging Project (KSHAP) (n = 1,724; mean age = 72.91 years) and examined how the proximal and distal characteristics of social networks predict loneliness using a hierarchical linear regression model. The study also investigated whether the major loss of social roles (marital and working status) influences perceived loneliness through the proximal and distal aspects of social networks by cross-sectional mediation analysis. RESULTS: This study found that the proximal (subjective number of connections) and distal (brokerage and embeddedness) aspects of social networks additively explained the frequency of loneliness. Moreover, the loss of late-life social roles (marital and working status) was related to an increase in loneliness, where the distal characteristic of social networks mediated this relationship. DISCUSSION/CONCLUSION: The results of this study suggest that the proximal and the distal characteristic of social networks is a social determinant predicting loneliness in late life. Besides, the loss of bridging and cohesive position among community networks may be a critical pathway to psychosocial transition after marital and working status changes.

Association between social network structure and physical activity in middle-aged Korean adults.

PURPOSE: Evidence suggests that physical activity participation is shaped through a myriad of structural aspects of social relationships. We examined the relationship between social network structure based on egocentric social network and physical activity. METHODS: From 6799 middle-aged Korean adults, we assessed the social network density and proportion of closed triads, using the name generator module. Self-reported physical activity for functional and leisure purposes was calculated in metabolic equivalent of task (MET)-min/week. We employed sex-stratified, multivariable linear regression to assess the association between each network structure variable and total physical activity, adjusting for age, network size, socioeconomic status, and comorbidities. We also examined the association with moderate-to-vigorous physical activity (MVPA) and wrist-worn accelerometer assessed physical activity. RESULTS: The network members of female participants were more likely to be of same sex and family member compared to those of males. There were no sex differences in average network size. Network density based on affiliation was sex-differentially associated with physical activity (male ß -346.7, p 0.2221 and female ß -528.6, p 0.0002). In parallel, the proportion of closed triads was negatively associated with physical activity only in females (male ß -542.6, p 0.0551 and female ß -641.51, p < 0.0001). However, network density and closed triads were insignificantly yet positively associated with MVPA in male (density ß 229.7, p 0.3193 and closed triad ß 109.21, p 0.6333). Network structure by contact frequency or emotional closeness and accelerometer-assessed physical activity showed inconsistent results. CONCLUSION: Understanding the role of social network structures can help to achieve ideal physical activity level in the context of primary prevention of cardiometabolic disorders.

Gender differences in the longitudinal association between husbands' and wives' depressive symptoms among Korean older adults: the moderating effects of the spousal relationship.

PURPOSE: The mutual effects of depressive symptoms between couples have long been reported; however, it remains unknown whether the spousal concordance in depressive symptoms differs depending on spousal relationships. METHOD: Data on 291 married couples from the Korean Social Life, Health, and Aging Project (KSHAP) were examined. The KSHAP collected global network data from the target population living in one Korean village over eight years and across five waves. A seemingly unrelated regression (SUR) model in the panel data was employed to address correlations and heterogeneity. RESULTS: If one spouse (husband or wife) had depressive symptoms, the other spouse tended to have depressive symptoms. However, the effect of marital relations on spousal concordance in depressive symptoms was different among husbands and wives. This study demonstrated both spousal support and spousal network aspects of spousal relationships. Depression concordance was stronger for couples with more negative marital relationship. A supportive marital relationship was associated with less concordance between spouses' depressive symptoms for wives but not for husbands. Spousal network overlap was associated with less depression concordance for husbands; however, for wives, spousal network overlap was directly associated with more depressive symptoms and did not mediate the association with depression concordance. CONCLUSION: Our findings suggest that approaches to supporting older adults dealing with mental health disorders may involve support at both the individual and couple levels. Gender-specific strategies could also be devised to improve the mental well-being of the older population.

Distributed functional connectivity predicts neuropsychological test performance among older adults.

Neuropsychological test is an essential tool in assessing cognitive and functional changes associated with late-life neurocognitive disorders. Despite the utility of the neuropsychological test, the brain-wide neural basis of the test performance remains unclear. Using the predictive modeling approach, we aimed to identify the optimal combination of functional connectivities that predicts neuropsychological test scores of novel individuals. Resting-state functional connectivity and neuropsychological tests included in the OASIS-3 dataset (n = 428) were used to train the predictive models, and the identified models were iteratively applied to the holdout internal test set (n = 216) and external test set (KSHAP, n = 151). We found that the connectivity-based predicted score tracked the actual behavioral test scores (r = 0.08-0.44). The predictive models utilizing most of the connectivity features showed better accuracy than those composed of focal connectivity features, suggesting that its neural basis is largely distributed across multiple brain systems. The discriminant and clinical validity of the predictive models were further assessed. Our results suggest that late-life neuropsychological test performance can be formally characterized with distributed connectome-based predictive models, and further translational evidence is needed when developing theoretically valid and clinically incremental predictive models.

Gender role stereotypes, patriarchal attitudes, and cognitive function in the elderly rural Korean population: a cross-sectional study.

OBJECTIVES: We analyzed whether gender role stereotypes (GRS) and patriarchal attitudes are associated with cognitive function in an elderly community. METHODS: We analyzed data from 580 people enrolled in the Korean Social Life, Health, and Aging Project. The degrees to which respondents held stereotypical beliefs about gender roles and had patriarchal mindsets were measured using a questionnaire. Based on participants' responses, we divided respondents into 2 groups-those with conservative mindsets and those with open mindsets-according to the median score for each of the 2 variables. Cognitive function was assessed using the Mini-Mental State Examination, Korean version (MMSE-K). Cognitive impairment was defined as an MMSE-K score ≤21 points. Multivariable logistic regression was performed, adjusting for gender, age, socio-demographic and lifestyle factors, and social network size. Age and lifestyle factors were stratified. RESULTS: Compared to those with open mindsets, those with conservative mindsets regarding gender roles and patriarchal norms had adjusted odds ratios of 1.88 (95% confidence interval [CI], 1.11 to 3.19) and 1.67 (95% CI, 1.00 to 2.79) for cognitive impairment, respectively. In the stratified analysis, subgroups with younger age and a good lifestyle maintained a protective association with cognitive impairment. CONCLUSIONS: GRS and a patriarchal mindset were marginally significantly associated with cognitive impairment among women later in life.

Computed Tomography-Derived Skeletal Muscle Radiodensity Predicts Peak Weight-Corrected Jump Power in Older Adults: The Korean Urban Rural Elderly (KURE) Study.

Computed tomography (CT)-derived skeletal muscle area (SMA) and skeletal muscle radiodensity (SMD) reflect distinctive quantitative and qualitative characteristics of skeletal muscles. However, data on whether CT-based muscle parameters, especially SMD, can predict muscle function is limited. In a prospective cohort, 1523 community-dwelling older adults who underwent abdominal CT scans and the countermovement two-legged jumping test on a ground reaction force platform were analyzed (mean age 74.7 years, 65.1% women). SMA and SMD were measured at third lumbar vertebra level (L3). Individuals with low jump power (peak weight-corrected jump power < 23.8 W/kg in men and < 19.0 W/kg in women using clinically validated threshold) were older; had lower SMA, SMD, and maximal grip strength values; and had lower chair rise test and timed up and go test performance than those without low jump power. SMD was positively associated with peak weight-corrected jump power (adjusted ß = 0.33 and 0.23 per 1 HU increase in men and women, respectively, p < 0.001). One HU decrement in SMD was associated with 10% elevated odds of low jump power (adjusted OR [aOR] 1.10, p < 0.001) after adjusting for age, sex, height, inflammation, and insulin resistance markers, whereas the association of SMA with low jump power was attenuated (aOR 1.00, p = 0.721). SMD showed better discrimination for low jump power than SMA (AUC 0.699 vs. 0.617, p < 0.001), with additional improvement when added to SMA and conventional risk factors (AUC 0.745 to 0.773, p < 0.001). Therefore, CT-measured L3 SMD can be a sensitive surrogate marker for muscle function along with SMA in older adults, which merits further investigation.

Neural and social correlates of attitudinal brokerage: using the complete social networks of two entire villages.

To avoid polarization and maintain small-worldness in society, people who act as attitudinal brokers are critical. These people maintain social ties with people who have dissimilar and even incompatible attitudes. Based on resting-state functional magnetic resonance imaging (n = 139) and the complete social networks from two Korean villages (n = 1508), we investigated the individual-level neural capacity and social-level structural opportunity for attitudinal brokerage regarding gender role attitudes. First, using a connectome-based predictive model, we successfully identified the brain functional connectivity that predicts attitudinal diversity of respondents' social network members. Brain regions that contributed most to the prediction included mentalizing regions known to be recruited in reading and understanding others' belief states. This result was corroborated by leave-one-out cross-validation, fivefold cross-validation and external validation where the brain connectivity identified in one village was used to predict the attitudinal diversity in another independent village. Second, the association between functional connectivity and attitudinal diversity of social network members was contingent on a specific position in a social network, namely, the structural brokerage position where people have ties with two people who are not otherwise connected.

All-cause mortality and three aspects of social relationships: an eight-year follow-up of older adults from one entire Korean village.

Various aspects of social relationships have been examined as risk factors for mortality. In particular, most research has focused on either loneliness or social disengagement. We aimed to extend the current research by adding a group-level segregation measure utilizing the whole social network of one entire village in South Korea. The analyses were based on the Korean Social Life, Health and Aging Project data collected over eight years across five waves. Of the 679 old adults who participated throughout the entire project (to wave 5), 63 were confirmed as deceased. All three aspects of social relationships examined, loneliness, social disengagement, and group-level segregation, were associated with mortality in the traditional Cox proportional hazard model without considering health-related time-varying covariates. However, a Cox marginal structural model, a counterfactual statistical measure that is designed to control for censoring bias due to sample attrition over the eight years and time-varying confounding variables, revealed that only group-level segregation was associated with mortality. Our results strongly suggest that more attention is needed on group-level segregation for mortality studies, as well as on well-known individual-level risk factors, including social disengagement and loneliness. All methods were carried out in accordance with relevant guidelines and regulations.

A measure of centrality in cyclic diffusion processes: Walk-betweenness.

Unlike many traditional measures of centrality based on paths that do not allow any repeated nodes or lines, we propose a new measure of centrality based on walks, walk-betweenness, that allows any number of repeated nodes or lines. To illustrate the value of walk-betweenness, we examine the transmission of syphilis in Chicago area and the diffusion of microfinance in 43 rural Indian villages. Walk-betweenness allows us to identify hidden bridging communities in Chicago that were essential in the transmission dynamics. We also find that village leaders with high walk-betweenness are more likely to accelerate the rate of microfinance take-up among their followers, outperforming other traditional centrality measures in regression analyses.

Social connectedness and hair cortisol in community-dwelling older adults.

Purpose: Hair cortisol is emerging as a reliable biomarker for measuring retrospective stress hormone levels. Given that social connectedness can buffer psychobiological stress reactivity, increasing attention is being paid to the specific types of social networks associated with the stress response. This study investigated the role played by two components of social life, emotional closeness and network size, to probe which aspects of social networks were related to stress measures. Methods: The scalp hair cortisol level was used to assess the cumulative cortisol production in 179 community-dwelling older adults, in the Korean Social Life, Health, and Aging Project (KSHAP). Multivariate regression approach was used to examine the link between the stress measures (cortisol and perceived stress scale) and social relationships (social network size and emotional closeness). Results: Emotional closeness (the average level of what one feels about one's relationship) was significantly associated with decreased levels of hair cortisol, whereas no such relationship was found with the network size. Conclusions: The current findings underscore the role of emotional support on reducing cumulative cortisol, thus providing potential resilience mechanisms for the psychobiological stress response.

Similarity in functional brain connectivity at rest predicts interpersonal closeness in the social network of an entire village.

People often have the intuition that they are similar to their friends, yet evidence for homophily (being friends with similar others) based on self-reported personality is inconsistent. Functional connectomes-patterns of spontaneous synchronization across the brain-are stable within individuals and predict how people tend to think and behave. Thus, they may capture interindividual variability in latent traits that are particularly similar among friends but that might elude self-report. Here, we examined interpersonal similarity in functional connectivity at rest-that is, in the absence of external stimuli-and tested if functional connectome similarity is associated with proximity in a real-world social network. The social network of a remote village was reconstructed; a subset of residents underwent functional magnetic resonance imaging. Similarity in functional connectomes was positively related to social network proximity, particularly in the default mode network. Controlling for similarities in demographic and personality data (the Big Five personality traits) yielded similar results. Thus, functional connectomes may capture latent interpersonal similarities between friends that are not fully captured by commonly used demographic or personality measures. The localization of these results suggests how friends may be particularly similar to one another. Additionally, geographic proximity moderated the relationship between neural similarity and social network proximity, suggesting that such associations are particularly strong among people who live particularly close to one another. These findings suggest that social connectivity is reflected in signatures of brain functional connectivity, consistent with the common intuition that friends share similarities that go beyond, for example, demographic similarities.