This study aimed to examine the association of social isolation and loneliness with frailty onset and interaction effects between social isolation and loneliness on frailty onset.
This three-year follow-up longitudinal study used data of independent older adults obtained from the Japan Gerontological Evaluation Study 2019–2022. After excluding those who were frail at baseline. The outcome variable was newly frailty onset measured by the Kihon Checklist (Satake et al, 2015, the possible score range: 0 to 25, ≥ 4 points; pre-frail, ≥ 8 points; frail). Exposure variables were social isolation and loneliness. Based on the frequency of social contacts, social isolation was classified into three categories: “not isolated” (≥ 4 times/week), “isolated tendency” (1-3 times/week), and “isolated” ( 1 time/week). Loneliness was assessed by the University of California, Los Angeles Loneliness Scale, and classified into three categories: “not lonely” (3 points), “lonely tendency” (4–5 points), and “lonely” (≥6 points). Possible confounders were included in the analysis. First, we employed modified Poisson regression analysis to examine the impact of social isolation and loneliness on frailty onset. Second, the interaction effect between social isolation and loneliness on frailty onset was calculated by Relative Excess Risk due to Interaction (RERI). Missing data were imputed by multiple imputations by chained equations.
A total of 8,440 participants were included in the analysis. The mean age was 73.8 ± 0.5 years; 50.7% were females. In 2022, 15.1% participants experienced frailty onset. Compared to “not isolated” group, “isolated” group had significantly higher risks of frailty onset (Risk Ratio [RR]= 1.37, 95 % Confidence Interval [CI]= 1.18–1.59). Compared to “not lonely” group, “lonely” group had significantly higher risks of frailty onset (RR= 1.77, 95% CI= 1.51–2.06). Compared to those with “not isolated” & “not lonely”, those with “not isolated” & “lonely” and those with “isolated” & “not lonely” had significantly higher risks of frailty onset (“not isolated” & “lonely” group: RR= 2.00, 95% CI= 1.54–2.59; “isolated” & “not lonely” group: RR= 1.44, 95% CI= 1.16–1,80). Those with “isolated” & “lonely” had significantly the highest risks of frailty onset among all groups (RR= 2.07, 95% CI= 1.58-2.70). Social isolation and loneliness showed a negative interaction with frailty onset (RERI: -0.37, 95% CI= -0.97–0.23).
Participants with both social isolation and loneliness had the highest risk of frailty onset. However, there was no significant interaction effect between social isolation and loneliness on frailty onset.
This study suggests that preventing social isolation and loneliness could protect against frailty onset among older adults. Older adults who feel lonely or socially isolated are more likely to be frail, rehabilitation team needs to promote social participation in the community.
loneliness
frailty
