Dual Trajectories of Social Isolation and Dementia in Older Adults: A Population-Based Longitudinal Study

Objectives: To identify the interrelations between the trajectories of social isolation and dementia in older adults. Methods: Data came from the National Health and Aging Trends Study 2011–2018 surveys. Group-based dual trajectory modeling was used to examine trajectories and their interrelations. Results: Four trajectories of social isolation—rarely isolated (62.2%), steady increase (13.5%), steady decrease (7.4%), and persistently isolated (16.9%) and dementia risk—persistently low risk (80.4%), increasing with early onset (3.9%), increasing with late onset (4.5%), and persistently high risk (11.2%) emerged. Two-thirds of the low-risk dementia group were in the rarely isolated group. The high-risk dementia group had the most overlap with the decreasing social isolation group (47%), followed by the persistently isolated group (28%). Conclusions: Social isolation and dementia mostly evolved in the same direction. However, the pattern of associations between these trajectories is intricate and may be reversed among long-term dementia survivors.