Social Isolation Changes and Long-Term Outcomes Among Older Adults

Abstract

Importance: While the association between cross-sectional measures of social isolation and adverse health outcomes is well established, less is known about the association between changes in social isolation and health outcomes.

Objective: To assess changes of social isolation and mortality, physical function, cognitive function, cardiovascular disease (CVD), and stroke.

Design, setting, and participants: In a cohort design, social isolation changes in 4 years and subsequent risk of mortality and other outcomes were assessed using the 13 649 eligible Health and Retirement Study (HRS) respondents from the 2006 to 2020 waves. Data were analyzed from October 11, 2023, to April 26, 2024.

Exposure: The main exposure was the change in social isolation measured by the Steptoe 5-item Social Isolation Index from the initial assessment to a second assessment conducted 4 years later. Participants were classified into decreased isolation, stable, or increased isolation groups, stratified by their baseline isolation status.

Main outcomes and measures: The primary outcomes were mortality, self-reported dependencies in activities of daily living, Alzheimer disease and Alzheimer disease-related dementia, CVD, and stroke. Dementia, CVD, and stroke were assessed using HRS-linked Medicare records. Incidence rates (IRs) of each group were estimated and a Cox proportional hazards regression model was used, with inverse-probability treatment weighting to adjust for confounders.

Results: Among 13 649 participants (mean [SD] age at baseline, 65.3 [9.5] years; 8011 [58.7%] women) isolated at baseline, those with increased isolation had higher mortality (n = 693; IR = 68.19; 95% CI, 60.89-76.36 per 1000 person-years) than those who were stable (n = 1796; IR = 44.02; 95% CI, 40.47-47.88 person-years) or had decreased isolation (n = 2067; IR = 37.77; 95% CI, 34.73-41.09 person-years) isolation. Increased isolation was associated with higher risks of mortality (adjusted hazard ratio [AHR], 1.29; 95% CI, 1.09-1.51), disability (AHR, 1.35; 95% CI, 1.09-1.67), and dementia (AHR, 1.40; 95% CI, 1.02-1.93) compared with stable isolation. Similar findings were observed among socially nonisolated participants at baseline.

Conclusions and relevance: In this cohort study, increased isolation was associated with elevated risks of mortality, disability, and dementia, irrespective of baseline isolation status. These results underscore the importance of interventions targeting the prevention of increased isolation among older adults to mitigate its adverse effects on mortality, as well as physical and cognitive function decline.

Figure 1.. Flowchart of the Analysis Cohort Selection

Among the 42 406 Health and Retirement Study (HRS) respondents in 2006 to 2020, we excluded 28 757 individuals. For disability, dementia, cardiovascular disease, and stroke outcomes, we further excluded individuals with no linked Medicare claims or with the outcome missing or the outcome before first measurement of social isolation. The flowcharts for the other 4 outcomes are listed in eFigure 1 in Supplement 1. LBQ indicates Leave-Behind Questionnaires.

Figure 2.. Cumulative Incidence Curves of Mortality, Disability, and Dementia for Social Isolation Change Groups, Stratified by Baseline Social Isolation Status

Disability was measured as an activities of daily living score greater than 0, and dementia was defined as Alzheimer disease or Alzheimer disease–related dementia. The cumulative incidences for cardiovascular disease and stroke are listed in eFigure 3 in Supplement 1. SII indicates Social Isolation Index.

Figure 3.. Incidence of Distal Outcomes for Social Isolation Change Groups, Stratified by Baseline Social Isolation Status

Disability was measured as an activities of daily living score greater than 0; dementia included Alzheimer disease or Alzheimer disease–related dementia. CVD indicates cardiovascular disease; error bars indicate 95% CI.

Figure 4.. Adjusted Hazard Ratios (AHRs) of Changes in Isolation of Distal Outcomes, Stratified by Baseline Isolation Status

The AHRs were weighted by probability for treatment weights. CVD indicates cardiovascular disease; error bars indicate 95% CI.