Dietary Inflammatory Index and Sleep Quality Among Women with Breast Cancer

Sleep disturbances are common among women with breast cancer (BC). Recent evidence suggests that dietary inflammation may influence sleep quality, yet this association remains underexplored in BC populations. In this cross-sectional study, 600 women aged 18–75 years with pathologically confirmed BC were recruited from the Isfahan Breast Cancer Registry between 2021 and 2023. Dietary intake was assessed using a validated 168-item Food Frequency Questionnaire (FFQ). Dietary Inflammatory Index (DII) and energy-adjusted DII (E-DII) scores were calculated based on 35 dietary components. Sleep quality was assessed using the validated Persian version of the Pittsburgh Sleep Quality Index (PSQI-P). A multiple linear regression model was employed to estimate adjusted regression coefficients. Higher DII and E-DII scores were significantly associated with poorer sleep quality. Each one-unit increase in DII and E-DII corresponded to a 0.34-point (95% CI: 0.11–0.57; p = 0.004) and a 0.34-point (95% CI: 0.14–0.53; p = 0.001) increase in PSQI score, respectively. A significant linear trend was observed across quartiles of DII and E-DII. Higher dietary inflammatory potential was associated with poorer sleep quality among women with BC. Considering the limitations of the cross-sectional design, longitudinal and interventional studies are needed to determine whether reducing dietary inflammatory potential can improve sleep outcomes in this population.