Diet Quality as Assessed by the Healthy Eating Index, Alternate Healthy Eating Index, Dietary Approaches to Stop Hypertension Score, and Health Outcomes: An Updated Systematic Review and Meta-Analysis of Cohort Studies

Background Diets of the highest quality have been associated with a significantly lower risk of noncommunicable diseases. Objective It was the aim of this study to update a previous systematic review investigating the associations of diet quality as assessed by the Healthy Eating Index (HEI), Alternate Healthy Eating Index (AHEI), and Dietary Approaches to Stop Hypertension (DASH) score and multiple health outcomes. As an additional topic, the associations of these diet quality indices with all-cause mortality and cancer mortality among cancer survivors were also investigated. Design A literature search for prospective cohort studies that were published up to May 15, 2017 was performed using the electronic databases PubMed, Scopus, and Embase. Summary risk ratios (RRs) and 95% CIs were estimated using a random effects model for high vs low adherence categories. Results The updated review process showed 34 new reports (total number of reports evaluated = 68; including 1,670,179 participants). Diets of the highest quality, as assessed by the HEI, AHEI, and DASH score, resulted in a significant risk reduction for all-cause mortality (RR 0.78, 95% CI 0.77 to 0.80; I-2 = 59%; n = 13), cardiovascular disease (incidence or mortality) (RR 0.78, 95% CI 0.76 to 0.80; I-2 = 49%; n = 28), cancer (incidence or mortality) (RR 0.84, 95% CI 0.82 to 0.87; I-2 = 66%; n = 31), type 2 diabetes (RR 0.82, 95% CI 0.78 to 0.85; I-2 = 72%; n = 10), and neurodegenerative diseases (RR 0.85, 95% CI 0.74 to 0.98; I-2 = 51%; n = 5). Among cancer survivors, the association between diets for the highest quality resulted in a significant reduction in all-cause mortality (RR 0.88, 95% CI 0.81 to 0.95; I-2 = 38%; n = 7) and cancer mortality (RR 0.90, 95% CI 0.83 to 0.98; I-2 = 0%; n = 7). Conclusions In the updated meta-analyses, diets that score highly on the HEI, AHEI, and DASH were associated with a significant reduction in the risk of all-cause mortality, cardiovascular disease, cancer, type 2 diabetes, and neurodegenerative disease by 22%, 22%, 16%, 18%, and 15%, respectively. Moreover, high-quality diets were inversely associated with overall mortality and cancer mortality among cancer survivors.