Changes in Loneliness, Social Isolation, and Social Support: A Gender-Disaggregated Analysis of Their Associations With Dementia and Cognitive Decline in Older Adults

Objectives: Limited evidence exists on the gender-specific impact of changes in loneliness, social isolation, and social support on dementia risk. We examined these changes and their relationships with dementia and cognitive decline. Methods: Data from over 12,000 community-dwelling Australians aged 70+ years without significant cognitive impairment at enrolment were analysed. Loneliness, social isolation, and social support were self-reported at baseline and ∼2 years later (social isolation and social support) or ∼3 years later (loneliness), classified as never, transient, incident, or persistent. Dementia diagnosis followed DSM-IV criteria, adjudicated by an expert panel. Gender-disaggregated Cox proportional hazards regressions were conducted, adjusting for age and other dementia risk factors. Results: At baseline, participants were aged 70–95 years (mean: 75.2 ± 4.3), with 54% being women. Overall, 81.1% of men and 71.7% of women reported never feeling lonely at baseline, while transient, incident, and persistent loneliness were experienced by 4.9%, 8.4%, and 5.5% of men and 8.5%, 11.6%, and 8.3% of women, respectively. Over a median 8-year follow-up, incident loneliness in men (HR: 1.52, 95% CI: 1.08–2.13) and persistent loneliness in women (HR: 2.14, 95% CI: 1.55–2.97) were associated with a greater dementia risk, compared to those who were never lonely. No increased risk was observed for transient loneliness. Despite the remarkably low prevalence of social isolation and poor social support in this initially healthy cohort, both were associated with cognitive decline (secondary outcome) but not with dementia risk. Conclusion: Persistent loneliness in people aged 70+, especially in women, was associated with a higher risk of dementia and cognitive decline.