Evolutionary-concordance lifestyle and diet and mediterranean diet pattern scores and risk of incident colorectal cancer in Iowa women

Background: Whereas diet and lifestyle are strongly implicated in the etiology of colorectal cancer, single exposures generally are weakly and inconsistently associated with the disease. Exposure patterns may be more helpful for investigating diet and lifestyle-colorectal cancer associations. Evolutionary-concordance diet and Mediterranean diet pattern scores were previously found to be inversely associated with colorectal adenoma. Methods: To investigate associations of these diet scores and an evolutionary-concordance lifestyle score (comprising smoking status, physical activity, and body mass index) with incident colorectal cancer, we analyzed data from the prospective Iowa Women's Health Study. Diet and lifestyle scores were calculated for each participant and categorized into quintiles, and associations estimated using Cox proportional hazards models. Results: Of the 35,221 55- to 69-year-old cancer-free women at baseline, 1,731 developed colorectal cancer during follow-up. The multivariable-adjusted HR comparing persons in the highest relative to the lowest quintile of the lifestyle score was 0.66 (95% confidence interval, 0.56-0.78; P_trend < 0.01). Although the estimated associations of the evolutionary-concordance diet and Mediterranean diet scores alone with colorectal cancer were null, relative to those in the lowest tertiles of both the evolutionary-concordance diet and lifestyle scores, those in the highest tertiles of both scores were at the lowest risk (P_interaction < 0.01). Conclusions: Our findings suggest that a more evolutionary-concordant lifestyle, alone and in interaction with a more evolutionary-concordant diet pattern, may be inversely associated with colorectal cancer risk. Impact: These results support further investigation of colorectal cancer etiology using evolutionary-concordance dietary and lifestyle pattern scores.