Gray matter volume covariance networks associated with social networks in older adults

Abstract

Extensive social networks are associated with better physical, mental, and cognitive health in aging, but the underlying brain substrates remain largely unexplored. Voxel-based morphometry and multivariate statistics were used to identify gray matter volume covariance networks associated with social networks in 86 older adults without dementia (M Age = 75.20 years, 53% women). Gray matter networks associated with the number of high-contact social roles and the total number of network members were identified after adjusting for age, sex, education, global health, and total intracranial volume - and shared nodes included medial, lateral and orbital prefrontal, hippocampal, precuneus, insular, and cingulate regions. Greater expression of these gray matter networks was associated with better memory scores on the Free and Cued Selective Reminding Test. A more distributed network was associated with high-contact social roles than total number of networks members - also extending into amygdala and entorhinal cortex. Thus, high-contact social roles and total number of network members in older adults are associated with gray matter networks composed of regions previously linked to memory and affected by both healthy aging and Alzheimer disease - and high-contact social roles are more strongly associated with brain structures than the total number of network members.

Keywords: Social networks; aging; multivariate statistics; neuroimaging.

Figure 1a:

Gray matter covariance patterns associated with the SNI-1 score (total number of high-contact roles of a respondent) in older adults without dementia. Shown are thresholded Z-loadings at |Z|>1.96 p < .05 (.025 in each tail). Positively weighted regions are displayed in blue, implying relatively larger volumes with SNI1-score. Negatively weighted regions are displayed in red, implying relatively smaller volumes with SNI1–1 score. All results are adjusted for age, sex, education, total intracranial volume, and global health status.

Figure 1b:

Gray matter covariance patterns associated with the SNI-2 score (total number of individuals in a respondent’s social network) in older adults without dementia. Shown are thresholded Z-loadings at |Z|>1.96 p < .05 (.025 in each tail). Positively weighted regions are displayed in blue, implying relatively larger volumes with SNI2-score. Negatively weighted regions are displayed in red, implying relatively smaller volumes with SNI-2 score. All results are adjusted for age, sex, education, total intracranial volume, and global health status.