Objective To explore the impact and mechanism of frailty on depression in elderly cancer patients.

Method Convenience sampling was used to select 198 elderly cancer patients. Sociodemographic and disease-related data were collected from the patients, and the frailty phenotype scale, social support scale, and elderly depression scale were used for investigation. Model 4 and Model 58 in the PROCESS 3.5 macro program were used for mediation effect testing.

Result The total frailty score of elderly cancer patients was (2.31 ± 0.641) points, with a depression score range of 3-14 points and an average score of (8.05 ± 2.84) points. The total social support score range was 35-50 points, with an average score of (42.10 ± 3.57) points; The frailty of elderly cancer patients was negatively correlated with social support and its various dimensions (r = –0.295 ~ –0.143, P ＜ 0.05). There was a positive correlation between frailty and elderly depression (r = 0.367, P ＜ 0.01). Social support played a partial mediating role between depression and age-related frailty, with a mediating effect accounting for 20.22 % of the total effect. The first half of the mediating effect of per capita monthly income of patients on social support has a moderating effect (B = –0.184, P ＜ 0.01), and the moderating effect of per capita monthly income of patients showed individual differences.

Conclusion The degree of frailty in elderly cancer patients not only directly affects depression, but can also be mediated by social support, and this process is regulated by the average monthly income of the patient's family.