Abstract: Objective: To explore the chain mediating effect of frailty and depression between dysfunction and pain catastrophizing in older patients with chronic low back pain. Methods: The study used a cross-sectional study design. A total of 253 older patients with chronic low back pain were recruited by convenience sampling in tertiary grade A hospital in Shanghai from February 2023 to November 2023. Patients were investigated by the Oswestry Disability Index, the FRAIL Frailty Scale, the Patient Health Questionnaire-9, and the Pain Catastrophizing Scale. The Process3.3 macro program was used to analyze the chain mediating effect of frailty and depression between patient dysfunction and pain catastrophizing. The Amos 28.0 was used to construct a structural equation model. Results: Disability index, frailty, depression and pain catastrophizing scores were positively correlated (r was from 0.496 to 0.741, P<0.01). Disability index had a positive effect on frailty (β=0.496, P<0.001). Disability index and frailty had a positive impact on depression (β=0.508 and 0.355, P<0.001). Disability index, frailty and depression had positive effects on pain catastrophizing (β=0.355, 0.244 and 0.351, P<0.001). The direct effect of disability index on pain catastrophizing was 0.330, accounting for 49.1% of the total effects. The total indirect effect of frailty and depression between disability and pain catastrophizing was 0.342, accounting for 50.9% of the total effects. The indirect effects of the frailty between dysfunction and pain catastrophizing, the depression between dysfunction and pain catastrophizing, and the frailty and depression between dysfunction and pain catastrophizing were 0.114, 0.169, and 0.059, respectively. Conclusion: The dysfunction of older patients with chronic low back pain can not only directly affect pain catastrophizing, but also indirectly affect pain catastrophizing through the mediating effect of frailty, depression, and the chain mediating effect of frailty and depression.

Key words: frailty; depression; chronic pain; pain catastrophizing; mediating effect; the elderly; chronic low back pain