Dietary inflammatory index, Mediterranean diet score, and lung cancer: a prospective study

Purpose To investigate prospectively the associations of Dietary Inflammatory Index (DII) and Mediterranean Diet Score (MDS) with lung cancer. Methods We used data from men and women aged 40-69 years at recruitment in 1990-1994, who were participants in the Melbourne Collaborative Cohort Study (n = 35,303). A total of 403 incident lung cancer cases were identified over an average 18-year follow-up. Hazard ratios (HR) were estimated using Cox regression, adjusting for smoking status and other risk factors, with age as the time metric. Results An inverse correlation was observed between the DII and MDS (rho = -0.45), consistent with a higher DII being pro-inflammatory and less 'healthy,' while a high MDS reflects a 'healthier' diet. The DII was positively associated with risk of lung cancer in current smokers [HRQ4 (vs) (Q1) = 1.70 (1.02, 2.82); P-trend = 0.008] (p interaction between DII quartiles and smoking status = 0.03). The MDS was inversely associated with lung cancer risk overall [HR7-9 (vs 0-3) = 0.64 (0.45, 0.90); P-trend = 0.005] and for current smokers (HR7-9 vs 0-3 = 0.38 (0.19, 0.75); P-trend = 0.005) (p interaction between MDS categories and smoking status = 0.31). Conclusions The MDS showed an inverse association with lung cancer risk, especially for current smokers. A high DII, indicating a more pro-inflammatory diet, was associated with risk of lung cancer only for current smokers. A healthy diet may reduce the risk of lung cancer, especially in smokers.