Mid-to-late-life social network size and resilience to neurodegeneration: The Framingham Heart Study.

backgroundSocial stimulation from having large networks may build cognitive reserve and contribute to cognitive resilience. However, limited research has assessed whether this relationship differs across the adult life course. We examined the relationship between social network size and resilience to neurodegeneration in memory, language, and executive function among mid-to-late-life adults.

methodsThe sample included 1,602 participants from the Framingham Heart Study Offspring cohort who completed the Berkman-Syme Social Network Index (SNI) questionnaire, had available plasma total tau (t-tau) measures at Exam 8, and had neuropsychological (NP) factor scores in memory, language, and executive function. Social network size was operationalized through a calculated SNI score and categorized into small, medium, and large networks. Cognitive resilience was operationalized using a residual approach by regressing each NP factor score on the plasma t-tau measure. Linear regression was used to assess associations between social network size and cognitive resilience, adjusting for age, sex, education, APOE ε4 allele carrier status, time between the most recent NP exam visit date and Exam 8 date, physical activity, smoking status, and depressive symptoms. Models were stratified by midlife (age 47-64 years) and late-life (age 65-91 years) groups.

resultsAverage age was 67 years with most participants identifying as female (n = 880; 55%). By age group, more participants were in the late-life group (n = 918; 57%) compared to the midlife group (n = 684; 43%). Large social network size was significantly associated with greater resilience to neurodegeneration in memory compared to small social network size (β = 0.07; 95% CI = 0.01-0.13). There were no significant associations between large social networks and resilience to neurodegeneration in language or executive function. No significant interactions between social network size and age group on resilience to neurodegeneration were observed in any of the domains examined. In the stratified models, large social networks were only associated with resilience to neurodegeneration in executive function among the midlife group (β = 0.11; 95% CI = 0.01-0.21).

conclusionsLarge social networks may promote greater resilience to neurodegeneration in memory among mid-to-late-life adults. Specific to middle-aged adults was a significantly greater resilience in executive function associated with large networks. These findings should be interpreted with caution, however, as estimate sizes are relatively small and potentially not robust, given the current sample size. Additional studies in larger and more diverse samples are needed to replicate and generalize our findings to other groups.