Trajectories of loneliness and the association of the risk of frailty among older adults: insights from a national cohort study

Loneliness is common in later life and is associated with increased morbidity, mortality, and functional decline, while frailty represents a state of heightened vulnerability due to multisystem age-related decline. This study examined how long-term patterns of loneliness relate to frailty risk among Chinese older adults using nationally representative longitudinal data. Data were drawn from four waves (2011, 2013, 2015, 2018) of the China Health and Retirement Longitudinal Study, including 2,073 community-dwelling adults aged ≥60 years who were non-frail at baseline and had complete loneliness and frailty data. Loneliness was assessed with a CES-D single item across all waves and group-based trajectory modeling identified distinct loneliness trajectories over seven years. Frailty was measured using a 31-item frailty index, and logistic regression estimated odds ratios (ORs) for incident frailty across trajectory groups, adjusting sequentially for sociodemographic factors, health behaviors, comorbidities, and baseline health status. Five loneliness trajectories were identified: stable low (67.9%), increasing (11.1%), decreasing (6.7%), fluctuating (8.5%), and stable high loneliness (5.8%). Over seven years, 510 participants (24.6%) developed frailty, with higher incidence in the increasing, fluctuating, and stable high groups compared with the stable low group. In fully adjusted models, increasing (OR=2.469, 95% CI 1.796–3.394), fluctuating (OR=1.799, 95% CI 1.250–2.588), and stable high loneliness (OR=3.989, 95% CI 2.613–6.090) trajectories remained significantly associated with incident frailty, whereas the decreasing trajectory was not. Distinct longitudinal patterns of loneliness are differentially associated with frailty risk, with increasing, fluctuating, and persistently high loneliness conferring substantially higher odds of frailty onset in later life. Older adults following these adverse loneliness trajectories may represent priority targets for prevention strategies aimed at reducing loneliness and strengthening social engagement to mitigate frailty risk. Not applicable.