Aging
Heterogeneity in the Population Attributable Fraction of Social Isolation for Incident Dementia Dylan Tran* Dylan Tran Tran Tran Tran Tran Tran Tran Tran Tran Tran Tran dttran@bu.edu
Social isolation is a potentially modifiable risk factor for dementia, but its population impact may vary across sociodemographic subgroups. We examine heterogeneity in the estimated population attributable fraction (PAF) of incident dementia attributable to social isolation.
Data were from the 2008–2020 Health and Retirement Study. Social isolation was measured at baseline using a six-item composite variable capturing marital status, living alone, monthly contact with children/family/friends, and participation in social activities with participants in the top quintile classified as isolated. Baseline exposure was defined as the first available assessment from 2008 or 2010. Incident dementia was defined using the Langa–Weir cognitive classification. We fit discrete-time pooled logistic models adjusting for age, sex, race and ethnicity, education, and urbanicity. Heterogeneity in RR was assessed using interaction terms and likelihood ratio tests. We computed Miettinen PAFs using the baseline prevalence of isolation among incident cases within subgroups and the overall RR when there was no evidence of interaction.
Among 11,402 participants followed for up to 12 years (mean age [SD] = 64.8 [11.7]), 58% women, 21.4% were classified as socially isolated at baseline (ranging from ~18% to ~45% across subgroups), and 598 (5.2%) developed incident dementia. Social isolation was associated with higher dementia risk (RR=1.19, 95% CI:0.99 to 1.45). Tests for interaction provided no evidence of effect heterogeneity, supporting the use of a common RR. The estimated PAF was 5.6% (95% CI: −0.23% to 11.5%). Although a common RR was used, subgroup-specific PAF point estimates varied (e.g. 6.8% for women, 3.2% for men), reflecting differences in the subgroup prevalence of social isolation.
These findings suggest that while RRs were similar across sociodemographic groups, population-level impact as measured by the PAF differed due to variation in the prevalence of social isolation.
