Dietary inflammatory index and non-Hodgkin lymphoma risk in an Italian case–control study

Background: While dietary factors have been shown to play an important etiologic role in non-Hodgkin lymphoma (NHL), little is known about the association between inflammatory properties of diet and NHL risk. Methods: We explored the association between the dietary inflammatory index (DII) and NHL risk in a multicenter Italian case–control study conducted between 1999 and 2014. Cases were 536 subjects with incident, histologically confirmed NHL from three areas in Italy. Controls were 984 subjects admitted to the same network of hospitals as the cases for acute, nonmalignant conditions, unrelated to diet. DII scores were computed based on 30 nutrients and food items assessed using a reproducible and validated 78-item food-frequency questionnaire. Odds ratios (ORs) were estimated through logistic regression models adjusting for age, total energy intake, and other recognized confounding factors. Results: Subjects in the highest quartile of DII scores (i.e., with the most pro-inflammatory diets) had a higher risk of NHL compared with subjects in the lowest quartile (i.e., with the most anti-inflammatory diets) (ORQuartile4vs1 1.61, 95% confidence interval CI 1.07–2.43; p-trend = 0.01). Stratified analyses produced stronger associations between DII and NHL among males (ORQuartile4vs1 2.14; 95% CI 1.25–3.67) with significant heterogeneity (p value = 0.02); when analyzed by histologic subtype, a significant association was observed with diffuse large B-cell lymphoma (ORQuartile4vs1 1.84; 95% CI 1.09–3.10). Conclusion: A pro-inflammatory diet, as indicated by higher DII scores, is associated with elevated odds of NHL, especially among males.