The Potential Mediating Role of Inflammation on the Association Between Dietary Inflammatory Index and Sleep Disturbance Among Breast Cancer Patients: A Cross-Sectional Study

Background: Sleep disturbance (SD) is very common in breast cancer (BC) patients, resulting in poor therapeutic efficacy and prognosis. Diet may be associated with SD through systemic inflammation. This study aimed to evaluate the association between the energy-adjusted Dietary Inflammatory Index (E-DII) and SD, as well as the potential mediating role of inflammatory biomarkers in patients with BC. Methods: In this cross-sectional study, 302 BC patients were recruited, from whom 103 blood samples were obtained for the determination of plasma inflammatory biomarkers. Dietary intake was evaluated using 3-day, 24 h dietary recalls, while SD was assessed using the Pittsburgh Sleep Quality Index (PSQI). Results: SD was observed in 91 (30.13%) patients, who exhibited significantly higher E-DII scores, C-reactive protein (CRP), interleukins (IL-1β, IL-6, and IL-10), and tumor necrosis factor-α (TNF-α) levels compared to non-SD participants (p < 0.05). After adjusting for covariates, for every 1-point elevation in E-DII, the risk of SD increased by 23.0% (OR = 1.23; 95% CI: 1.04, 1.44; p = 0.014). Among the E-DII components, only vitamin C showed an inverse correlation with SD (OR = 0.99; 95% CI: 0.99, 1.00; p = 0.015). Mediation analysis showed that IL-1β, IL-10, IL-6, TNF-α, and CRP statistically mediated the association between E-DII and SD (all p < 0.05). The sensitivity parameters ρ were 0.3, 0.5, 0.4, 0.4, and 0.4, respectively. Conclusions: A diet with pro-inflammatory potential was correlated with SD among BC patients, which might be mediated by circulating IL-1β, IL-10, IL-6, TNF-α, and CRP.