Objectives To examine the mediating effect of quality of life (QoL) on the relationship between perceived stress and immune function in Korean family caregivers of patients with cancer.

Methods In this cross-sectional study, 89 family caregivers of patients with cancer completed perceived stress and QoL questionnaires. Immune function was assessed using two proinflammatory biomarkers, IL-6 and tumour necrosis factor-alpha (TNF-α). Multiple parallel mediator regression was conducted using four mediators (burden, lifestyle disruption, positive adaptation and financial concern) representing the subscales of QoL related to caregiving.

Results Psychological (indirect effect (ab)=−0.52, 95% CI −1.25 to −0.01) and physical (ab=−0.44, 95% CI −1.07 to −0.05) stress had a significant indirect effect on IL-6 levels attributed to lifestyle disruption associated with caregiving. Psychological (ab=−0.97, 95% CI −2.37 to −0.11) and physical (ab=−1.10, 95% CI −2.87 to −0.08) stress also had a significant indirect effect on TNF-α as a result of financial concerns owing to caregiving. Other indirect effects of psychological/physical stress on inflammation were not significant.

Conclusion This study demonstrated that the effects of perceived psychological and physical stress on IL-6 and TNF-α levels were mediated by the caregiver’s QoL, especially lifestyle disruption and financial concerns. Stress management and improvement of caregivers’ QoL related to lifestyle disruption and financial issues should be considered to reduce the negative effects of caregiving on immune function.