The Characteristics of Social Network Structure in Later Life in Relation to Incidence of Mild Cognitive Impairment and Conversion to Probable Dementia

Background: Larger, more active social networks are estimated to be associated with lower risks of cognitive decline. However, roles of various social relationships in a broad social network in protecting against cognitive decline remain to be elucidated. Objective: We aimed to investigate how social roles within a social network and number of social network members are associated with cognitive decline. Methods: Six waves of National Health and Aging Trends Study (2011-2016, NHATS) were utilized to examine the development of mild cognitive impairment (MCI) and probable dementia determined using validated criteria. Multivariable-adjusted multi-state survival models were used to model incidences and transitions, jointly with misclassification errors. Results: A total of 6,078 eligible NHATS participants were included (average age: 77.49±7.79 years; female: 58.42%; non-Hispanic white: 68.99%). Multivariable-adjusted analyses revealed that having more social network members was associated with lower hazards of conversion from MCI to probable dementia (adjusted Hazard Ratio; aHR=0.82; 95%confidence intervals; 95%CI=[0.67-0.99]), meanwhile having at least one college-educated family member within a social network was associated with lower incidence of probable dementia (aHR=0.37 [0.26-0.51]). Having at least one friend within a social network was associated with a lower hazard of incidence of probable dementia (aHR=0.48 [0.33-0.71]), but a higher risk of mortality in the MCI group (aHR=2.58 [1.47-4.51]). Conclusion: Having more social network members, having at least one friend, and having at least one college-educated family member within a social network, were associated with lower risks of incidence of dementia or conversion from MCI to dementia.