Dietary inflammatory index and risk of colorectal adenoma: effect measure modification by race, nonsteroidal anti-inflammatory drugs, cigarette smoking and body mass index?

Purpose To investigate if the association between dietary inflammatory potential and colorectal adenoma (CRA) is modified by race and factors known to modulate inflammation. Methods We examined effect measure modification of race, nonsteroidal anti-inflammatory drugs (NSAIDs), cigarette smoking and body mass index (BMI) on the diet-CRA association by employing energy-adjusted dietary inflammatory index (E-DII™) to characterize dietary inflammatory potential among 587 cases and 1,313 controls participating in a colonoscopy screening-based cross-sectional study of CRA. Participants completed a food frequency questionnaire from which E-DII score was derived. E-DII score was calculated from 34 food parameters (constituents), utilizing an energy-adjusted global comparative database to compute z scores from which centered proportions were summed to create the score. CRA cases were defined as individuals whose colonoscopy detected at least one pathologically confirmed adenomatous polyp. Unconditional logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs). Results A pro-inflammatory diet was not statistically significantly associated with elevated CRA risk (OR 1.07; 95% CI 0.97–1.19; p value = 0.18) in the multivariate regression model. NSAIDs use (OR never-users 1.19; 95% CI 1.03–1.38; OR ever-users 0.96; 95% CI 0.83–1.12; P interaction = 0.04) and race (OR African Americans 1.22; 95% CI 1.03–1.44; OR European Americans 0.99; 95% CI 0.86–1.14; P interaction = 0.14) appeared to modify the association, whereas cigarette smoking and BMI did not ( P interaction = 0.40 and 0.78, respectively). Conclusion NSAIDs use and race may modify the diet-CRA association. Further investigation in prospective cohort studies is warranted to confirm these findings.