Health-related quality of life as a mediator of the association between sleep quality and depressive symptoms in patients with gastric cancer

Depressive symptoms are common among patients with gastric cancer (GC) and are associated with poor sleep and impaired health-related quality of life (HRQoL). We examined the associations among sleep quality, HRQoL, and depressive symptoms and assessed cross-sectional statistical indirect associations through HRQoL dimensions. This cross-sectional study included 456 patients with pathologically confirmed GC at a tertiary hospital in southeastern China. Sleep quality, HRQoL, and depressive symptoms were assessed using the Pittsburgh Sleep Quality Index (PSQI), EORTC QLQ-C30 and QLQ-STO22, and Patient Health Questionnaire-9 (PHQ-9), respectively. Overall, 138 participants (30.3%) had depressive symptoms (PHQ-9 ≥ 5), including 41 (9.0%) with PHQ-9 scores ≥ 10. Poor sleep quality (PSQI > 5) was associated with higher odds of depressive symptoms at both thresholds (adjusted OR, 8.05 and 8.18, respectively; both P < 0.001). Each 1-SD increase in PSQI score was associated with adjusted ORs of 3.68 (95% CI, 2.75–4.94) and 2.35 (95% CI, 1.77–3.11), respectively. Emotional functioning, insomnia, and cancer-related anxiety were consistently associated with both outcomes in multivariable models. In separate mediation models, emotional functioning, fatigue, and cancer-related anxiety accounted for 24.77%-36.79% of the observed association. Poorer sleep quality was strongly associated with depressive symptoms in patients with GC. Several HRQoL dimensions showed partial statistical indirect associations. Because all variables were measured concurrently, these results do not establish temporal or causal mediation.