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

To evaluate the association between diet in relation to its inflammatory property and bladder cancer (BC) risk.

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.

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).

A pro-inflammatory diet as indicated by higher DII scores is associated with increased BC risk.