Social brain volume is associated with in-degree social network size among older adults.

The social brain hypothesis proposes that large neocortex size evolved to support cognitively demanding social interactions. Accordingly, previous studies have observed that larger orbitofrontal and amygdala structures predict the size of an individual's social network. However, it remains uncertain how an individual's social connectedness reported by other people is associated with the social brain volume. In this study, we found that a greater in-degree network size, a measure of social ties identified by a subject's social connections rather than by the subject, significantly correlated with a larger regional volume of the orbitofrontal cortex, dorsomedial prefrontal cortex and lingual gyrus. By contrast, out-degree size, which is based on an individual's self-perceived connectedness, showed no associations. Meta-analytic reverse inference further revealed that regional volume pattern of in-degree size was specifically involved in social inference ability. These findings were possible because our dataset contained the social networks of an entire village, i.e. a global network. The results suggest that the in-degree aspect of social network size not only confirms the previously reported brain correlates of the social network but also shows an association in brain regions involved in the ability to infer other people's minds. This study provides insight into understanding how the social brain is uniquely associated with sociocentric measures derived from a global network.

Social network properties and self-rated health in later life: comparisons from the Korean social life, health, and aging project and the national social life, health and aging project.

BACKGROUND: This paper has two objectives. Firstly, it provides an overview of the social network module, data collection procedures, and measurement of ego-centric and complete-network properties in the Korean Social Life, Health, and Aging Project (KSHAP). Secondly, it directly compares the KSHAP structure and results to the ego-centric network structure and results of the National Social Life, Health, and Aging Project (NSHAP), which conducted in-home interviews with 3,005 persons 57 to 85 years of age in the United States. METHODS: The structure of the complete social network of 814 KSHAP respondents living in Township K was measured and examined at two levels of networks. Ego-centric network properties include network size, composition, volume of contact with network members, density, and bridging potential. Complete-network properties are degree centrality, closeness centrality, betweenness centrality, and brokerage role. RESULTS: We found that KSHAP respondents with a smaller number of social network members were more likely to be older and tended to have poorer self-rated health. Compared to the NSHAP, the KSHAP respondents maintained a smaller network size with a greater network density among their members and lower bridging potential. Further analysis of the complete network properties of KSHAP respondents revealed that more brokerage roles inside the same neighborhood (Ri) were significantly associated with better self-rated health. Socially isolated respondents identified by network components had the worst self-rated health. CONCLUSIONS: The findings demonstrate the importance of social network analysis for the study of older adults' health status in Korea. The study also highlights the importance of complete-network data and its ability to reveal mechanisms beyond ego-centric network data.

Educational gradient in social network changes at disease diagnosis.

This study examines the educational gradient in social network changes following the diagnosis of new chronic diseases. Using a representative sample of the US older population, the author shows that the network size and amount of health-related discussion with social network members increased only for older adults with a bachelor's degree. Tie-level analyses reveal that such increase is from the activation of health discussion with the existing social network members, but not from the changes in discussion partners. These results suggest that heterogeneous temporal dynamics in social networks may be one mechanism that shapes diverging health trajectories in later life.

Health, Wealth, and Voting Trajectories in Later Life.

OBJECTIVES: Much of what we know about voting behaviors is based on cross-sectional comparisons of voters at different ages. This study draws on a unique linkage between the Wisconsin Longitudinal Study and state voter files to characterize voting trajectories in later life and explore their determinants. METHODS: Using sequence analysis, we identify 5 voting typologies based on turnout and voting methods over 8 biennial elections. Using multinomial logistic and Poisson regressions, we examine the role of physical, cognitive, and mental health and wealth in shaping enfranchisement and civic participation at older ages. RESULTS: Health and wealth are both positively associated with voter turnout, but the negative impact of poor health on voting declines with increasing wealth. Voting at the polls and early voting are more common among healthier older adults, whereas absentee voting is more common among older voters who are more affluent, less healthy, or both. Among those less wealthy, absentee methods mitigate the impact of poor health for previously active voters, but do not compensate for a lower turnout rate. In addition to physical and cognitive limitations, emotional difficulties and depression reduce turnout, particularly among the least wealthy. DISCUSSION: In this sample of older, largely White, primarily Midwestern committed voters, civic participation at older ages is shaped by individual experiences with wealth and health across the life course as well as political structures that facilitate or restrict the ability of individuals to consistently participate in elections.

Out of Sync, Out of Society: Political Beliefs and Social Networks.

Who is more likely to be isolated from society in terms of political beliefs? To answer this question, we measure whether individuals' beliefs are "out of sync" - the extent to which their views differ with their contemporaries - and examine how the level of synchronization is associated with the size of important-matter and political-matter discussion networks. The results show that people with weaker belief synchronization are more likely to have smaller important-matter discussion networks. However, additional analyses of political-matter discussion networks show that weaker belief synchronization is associated with smaller networks only among those without a high school diploma and even provides some advantage in maintaining larger networks for the college-educated. Overall, the results imply that political beliefs that are "out of sync" correspond to the individual being "out of society," whereas the aspects of "out of society" are quite different among educational groups.

The Association between Social Network Betweenness and Coronary Calcium: A Baseline Study of Patients with a High Risk of Cardiovascular Disease.

AIM: The association of social networks with cardiovascular disease (CVD) has been demonstrated through various studies. This study aimed to examine the association between social network betweenness -a network position of mediating between diverse social groups-and coronary artery calcium. METHODS: The data of 1,384 participants from the Cardiovascular and Metabolic Disease Etiology Research Center-High Risk Cohort, a prospective cohort study enrolling patients with a high risk of developing CVD (clinicaltrials.gov: NCT02003781), were analyzed. The deficiency in social network betweenness was measured in two ways: only-family networks, in which a respondent had networks with only family members, and no-cutpoint networks, in which the respondent does not function as a point of bridging between two or more social groups that are not directly connected. RESULTS: Participants who had higher coronary artery calcium scores (CACSs) were likely to have a smaller network size (p＜0.001), only-family networks (p＜0.001), and no-cutpoint networks (p＜0.001). Multiple logistic regression analyses revealed no significant association between network size and CACS. Only no-cutpoint networks had a significant relationship with CACS ＞400 (odds ratio, 1.72; 95% confidence interval, 1.07-2.77; p=0.026). The association was stronger among older (age ＞60 years) and female respondents. CONCLUSION: Deficiency in social network betweenness is closely related to coronary calcium in participants with a high risk of CVD. To generalize these results to a general population, further study should be performed.

Brain functional connectivity difference in the complete network of an entire village: the role of social network size and embeddedness.

Social networks are known to protect cognitive function in old age. For the first time, this study examines how social network size and social network embeddedness measured by k-core score are associated with functional connectivity in the brain using the complete social network of an entire village. According to the results, social network size has both positive and negative associations with functional connectivity; showing no meaningful pattern relative to distance among brain regions. However, older adults deeply embedded in the complete network tend to maintain functional connectivity between long-distance regions even after controlling for other covariates such as age, gender, education, and Mini-Mental State Examination score. Network Based Statistics (NBS) also revealed strong and consistent evidence that social network embeddedness has component-level associations with functional connectivity among brain regions, especially between inferior prefrontal and occipital/parietal lobes.

Factors Associated with Insomnia among the Elderly in a Korean Rural Community.

OBJECTIVE: Sleep disturbance is common in the elderly, which is result from multi-factorial causes encompassing socio-demographic, behavioral, and clinical factors. We aimed to identify factors associated with insomnia among the elderly in a rural community in South Korea, a country with a rapidly growing aged population. METHODS: This cross-sectional study used the data from the second wave of the Korean Social life, Health and Ageing Project, which is a cohort study of individuals living in a typical rural community in South Korea. Socio-demographic, behavioral, and clinical characteristics were obtained through face-to-face interviews. Various factors suspected to be associated with insomnia were compared between elderly participants with and without insomnia, and multiple logistic regression analyses were conducted to identify independent risk factors for insomnia. RESULTS: We found that 32.4% of 509 participants (72.8±7.7 years old) had insomnia. Female sex [odds ratio (OR)=2.19], low education level (OR=2.44), current smoking (OR=2.26), number of chronic diseases (OR=2.21 for 2-3 chronic diseases; OR=2.06 for 4 or more chronic diseases), and depression (OR=2.53) were independently associated with insomnia. CONCLUSION: We found that sex, education, chronic disease, and depression independently increase the risk of insomnia of the elderly in a Korean rural community. To overcome the elderly's insomnia, interventions should target modifiable factors such as depression. To promote active aging, longitudinal studies of factors associated with insomnia among the elderly should be performed in different regions and communities.

Social network types among older Korean adults: Associations with subjective health.

With population aging now a global phenomenon, the health of older adults is becoming an increasingly important issue. Because the Korean population is aging at an unprecedented rate, preparing for public health problems associated with old age is particularly salient in this country. As the physical and mental health of older adults is related to their social relationships, investigating the social networks of older adults and their relationship to health status is important for establishing public health policies. The aims of this study were to identify social network types among older adults in South Korea and to examine the relationship of these social network types with self-rated health and depression. Data from the Korean Social Life, Health, and Aging Project were analyzed. Model-based clustering using finite normal mixture modeling was conducted to identify the social network types based on ten criterion variables of social relationships and activities: marital status, number of children, number of close relatives, number of friends, frequency of attendance at religious services, attendance at organized group meetings, in-degree centrality, out-degree centrality, closeness centrality, and betweenness centrality. Multivariate regression analysis was conducted to examine associations between the identified social network types and self-rated health and depression. The model-based clustering analysis revealed that social networks clustered into five types: diverse, family, congregant, congregant-restricted, and restricted. Diverse or family social network types were significantly associated with more favorable subjective mental health, whereas the restricted network type was significantly associated with poorer ratings of mental and physical health. In addition, our analysis identified unique social network types related to religious activities. In summary, we developed a comprehensive social network typology for older Korean adults.