Social isolation and 9-year dementia risk in community-dwelling Medicare beneficiaries in the United States.

Background: Social isolation can influence whether older adults develop dementia. We examine the association between social isolation and incident dementia among older adults in a nationally representative sample of community dwelling older adults in the United States (U.S.). We also investigate whether this association varies by race and ethnicity.

Methods: Data (N = 5022) come from the National Health and Aging Trends Study, a longitudinal and nationally representative cohort of older adults in the U.S. A composite measure of social isolation was used to classify older adults as socially isolated or not socially isolated at baseline. Demographic and health factors were measured at baseline via self-report. Dementia was measured at each round of data collection. Discrete-time proportional hazard time-to-event models were used to assess the association between social isolation and incident dementia over 9 years (2011-2020).

Results: Of 5022 older adults, 1172 (23.3%) were socially isolated, and 3850 (76.7%) were not socially isolated. Adjusting for demographic and health factors, being socially isolated (vs. not socially isolated) was associated with a 1.28 (95% CI: 1.10-1.49) higher hazard of incident dementia over 9 years. There was no statistically significant difference by race and ethnicity.

Conclusion: Social isolation among older adults is associated with greater dementia risk. Elucidating the pathway by which social isolation impacts dementia may offer meaningful insights for the development of novel solutions to prevent or ameliorate dementia across diverse racial and ethnic groups.