Longitudinal relationships between frailty and psychological symptoms in middle-aged and older adults: a cross-lagged panel network analysis in UK Biobank

BACKGROUND: Frailty and psychological symptoms are closely related in middle-aged and older adults, but symptom-specific and temporal relationships remain unclear. We examined their cross-sectional and prospective associations using a network approach. METHOD: Data were obtained from 38,130 UK Biobank participants aged ≥45 years assessed at two time points. Frailty was measured using an adapted Fried phenotype, and four psychological symptoms were assessed: depressed mood, unenthusiasm/disinterest, tenseness/restlessness, and tiredness/lethargy. Cross-sectional network, cross-lagged panel network (CLPN), and sex-specific analyses were conducted. RESULTS: Cross-sectional networks showed associations between frailty and psychological symptoms, with tiredness/lethargy most prominently associated with frailty at both time points. Cross-lagged associations were generally modest. Depressed mood had the highest out-expected influence, whereas tiredness/lethargy had the highest in-expected influence. Findings for tiredness/lethargy should be interpreted cautiously because of overlap with the exhaustion component of frailty. Sex-specific networks were broadly similar. CONCLUSIONS: Frailty and psychological symptoms showed cross-sectional and prospective associations. Depressed mood occupied a central network position, although cross-lagged associations were modest. Findings are hypothesis-generating and should be interpreted considering limited symptom coverage and measurement constraints.