Dietary Inflammatory Index and risk of breast cancer: evidence from a prospective cohort of 67,879 women followed for 20 years in France

BackgroundInflammation is implicated in breast cancer development, and diet is one of the modifiable risk factors involved in the regulation of chronic inflammation. Previous studies on the association between breast cancer risk and Dietary Inflammatory Indexes (DII) derived from food frequency questionnaires and data on inflammatory potential of dietary components have reported inconsistent results.ObjectiveTo investigate the association between the DII and the risk of breast cancer using data from a large population-based cohort study.DesignA total of 67,879 women from the E3N cohort were followed from 1993 to 2014. A total of 5686 breast cancer cases were diagnosed during the follow-up. The food frequency questionnaire administered at baseline in 1993 was used to calculate an adapted DII. Cox proportional hazard models using age as the time scale were used to estimate hazard ratios (HR) and 95% confidence intervals (CI). Spline regression was used to determine any dose-response relationship. We also evaluated effect modification by menopausal status, body mass index, smoking status and alcohol consumption.ResultsThe median DII score of the study population was slightly pro-inflammatory (DII = + 0.39); ranged from - 4.68 in the lowest quintile to + 4.29 in the highest quintile. The HR increased linearly with the DII (HR per 1SD = 1.04 [95% CI: 1.01, 1.07]), and reached 1.13 [95% CI: 1.04, 1.23] in the 5th quintile group as compared to the first. A positive linear dose-response relationship was also observed when modeling DII with spline functions. Slightly higher HRs were observed in non-smokers (HR (for 1-SD increase) 1.06 [95% CI: 1.02, 1.10]; p trend = 0.001) and in low-alcohol consumers (<= 1 glass/day) (HR (for 1-SD increase) 1.05 [95% CI: 1.01, 1.08]; p trend = 0.002).ConclusionOur results suggest a positive association between DII and breast cancer risk. Consequently, the promotion of anti-inflammatory diet may contribute to breast cancer prevention.