Dual Pathways of Social Support in Loneliness and Frailty Among Older Adults with Diabetes: A Cross-Sectional Study on Mediation and Moderation Mechanism

Background: The mechanisms linking loneliness to frailty in older adults with diabetes remain unclear. Guided by the Loneliness-Health Outcomes Model, this study investigates the dual mediating and moderating roles of social support in this relationship to inform targeted community interventions. Methods: A cross-sectional study enrolled 442 community-dwelling adults aged ≥60 with Type 2 Diabetes in Beijing. Standardized scales assessed loneliness (UCLA Loneliness Scale), Tilburg Frailty Indicator (TFI), and social support (SSRS). Analyses included Pearson correlations, hierarchical regression, and PROCESS macro to evaluate mediation/moderation effects, adjusting for demographics and comorbidities. Results: Frailty prevalence was 55.2%. Loneliness positively correlated with frailty (r = 0.327, p < 0.01), while social support showed inverse associations with both loneliness (r = -0.496) and frailty (r = -0.315) (p < 0.01). Social support partially mediated loneliness’s effect on frailty (indirect effect: 30.86%; 95% CI: 0.028–0.087) and moderated this relationship (interaction β = -0.003, p = 0.011). Objective social support (β = -0.154, p < 0.001) and loneliness (β = 0.059, p = 0.002) independently predicted frailty. High-risk clusters (e.g., aged ≥80 years, widowed, isolated individuals) exhibited combined “high loneliness–low support–high frailty” profiles. Conclusions: Social support reduces frailty risk through dual mechanisms, highlighting the need to strengthen community care networks for objective support delivery and prioritize interventions for vulnerable subgroups. These findings advance psychosocially informed strategies for diabetes management in aging populations.