Background: The inflammatory potential of diet that has been shown to be associated with cancer risk. We examined the association between dietary inflammatory potential as measured by the dietary inflammatory index (DII®) and risk of upper aerodigestive tract cancers in a Japanese case-control study. Results: A positive association was observed between increasing DII scores and overall upper aerodigestive tract cancers, and across anatomic subsites. For upper aerodigestive tract cancers, the ORQ4vsQ1 = 1.73 (95% CI: 1.37-2.20); head and neck cancer, the ORQ4vsQ1 was 1.92 (95% CI: 1.42-2.59); and for esophageal cancer, the ORQ4vsQ1 was1.71 (95% CI: 1.54-1.90). Risks for hypopharyngeal and nasopharyngeal cancers were greatly elevated: (ORQ4vsQ1 = 4.05 (95% CI: 1.24-13.25) for hypopharyngeal cancer and ORQ4vsQ1 = 4.99 (95% CI: 1.14-21.79) for nasopharyngeal cancer. Conclusion: A more pro-inflammatory diet was associated with an elevated risk of upper aerodigestive tract cancers after accounting for important confounders. All anatomic subsites, except larynx, showed the consistently elevated risk with increasing DII score. Those subsites with known etiological associations with persistent infection showed the largest elevation in risk. These results warrant further evaluation in future studies. Materials and Methods: This is a case-control study of 1,028 cases and 3,081 age- and sex-matched non-cancer controls recruited at Aichi Cancer Center. DII scores were computed based on estimates of macro- and micro-nutrients from a self-administered food frequency questionnaire. Scores were further categorized into quartiles (based on the distribution in controls). Conditional logistic regression models were fit to estimate odds ratio (OR) and 95% confidence intervals (CIs) adjusted for smoking, ethanol consumption, alcohol flushing, number of teeth, and occupation group.
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