The Association between Trajectories of Loneliness and Physical Frailty in Chinese Older Adults: Does Age Matter?

Background: The present study aimed to examine age differences in the relationship between trajectories of loneliness and physical frailty among Chinese older adults. Methods: A total of 4618 participants aged ≥60 years old were taken from pooled data created from the 2011–2015 China Health and Retirement Longitudinal Study (CHARLS). Loneliness was assessed by a single question from the Centre for Epidemiological Studies scale, whereas physical frailty (PF) was examined by the physical frailty phenotype scale. We characterized trajectories of loneliness and PF using transition types and changes within the survey period. Results: Logistic regression models revealed that baseline loneliness was significantly related to remaining robust PF (OR = 0.55, 95% CI = 0.49–0.63, p < 0.001) and worsening in PF (OR = 1.17, 95% CI = 1.05–1.30, p < 0.01) at follow-up. Baseline PF status was also significantly related to the transitions in loneliness (worsen: OR = 1.41, 95% CI = 1.11–1.78, p < 0.01; improve: OR = 0.65, 95% CI = 0.47–0.91, p < 0.05). The cross-lagged panel model found that baseline PF or loneliness had a significant predictive effect on the changes in each other. The associations between trajectories of loneliness and PF were weakened with age and clustered in the under 75 age groups. Conclusions: Bidirectional associations may exist between trajectories of loneliness and PF among Chinese older adults. Interventions should mainly target the young-old to reduce the adverse reciprocal effects of loneliness and PF.