Quality of life and pain in Chinese lung cancer patients: Is optimism a moderator or mediator?

Objective: To clarify if optimism exerts a primarily moderating or mediating influence on the pain-QoL association in Chinese lung cancer patients. Methods: About 334 Chinese lung cancer patients were interviewed at baseline during the first outpatient visit (Baseline), at 4 months after Baseline (FU1), and at 8 months after Baseline (FU2). Respondents completed the Chinese version of the FACT-G version-3 scale (FACT-G (Ch)). Optimism and pain were assessed using two 11-point self-rated items. Linear mixed effects (LME) models tested the moderating and mediating effects of optimism on QoL. Results: Optimism, pain, and QoL were most strongly correlated at FU1. LME models failed to show any moderating effect by optimism on the pain-QoL association (standardized beta = -0.049, 95% CI -0.097 to 0.001). After adjustment for age, cancer stage, and disease recurrence, a modest mediating effect was observed for optimism on the pain-QoL association over the duration of the study (standardized beta = 0.047; Sobel test z = -4.317, p < 0.001). Conclusions: Optimism qualifies as a mediator between pain and QoL suggesting that pessimistic lung cancer patients are likely to experience greater QoL decrements in response to pain in the early post-diagnostic period. Effective pain control may be enhanced by inclusion of interventions that facilitate optimistic perspectives in patients. This study lends further support to the view that lung cancer patients' psychological needs are important in both pain control and QoL.