Dietary Inflammatory Index and Risk of Bladder Cancer in a Large Italian Case-control Study

Objective: To evaluate the association between diet in relation to its inflammatory property and bladder cancer (BC) risk. Methods: In this study we explored the association between the dietary inflammatory index (DII) and BC risk in an Italian case-control study conducted between 2003 and 2014. Cases were 690 patients with incident and histologically confirmed BC from 4 areas in Italy. Controls were 665 cancer-free subjects admitted to the same network of hospitals as cases for a wide spectrum of acute, non-neoplastic conditions. The DII was computed based on dietary intake assessed using a reproducible and valid 80-item food frequency questionnaire. Odds ratios (OR) were estimated through logistic regression models adjusting for age, sex, total energy intake, and other recognized confounding factors. Results: Subjects in the highest quartile of DII scores (ie, with a more pro-inflammatory diet) had a higher risk of BC compared to subjects in the lowest quartile (ie, with an anti-inflammatory diet) (OR_Quartile4vs1 = 1.97; 95% [confidence interval], 1.28, 3.03; P trend = .003). Stratified analyses produced stronger associations between DII and BC risk among females (OR_Quartile4vs1 = 5.73; 95% CI = 1.46, 22.44), older ≥65 years (OR_Quartile4vs1 = 2.45; 95% CI = 1.38, 4.34), subjects with higher education ≥7 years (OR_Quartile4vs1 = 2.22; 95% CI = 1.27, 3.88), and never smokers (OR_Quartile4vs1 = 4.04; 95% CI = 1.51, 10.80). Conclusion: A pro-inflammatory diet as indicated by higher DII scores is associated with increased BC risk.