Diet quality as assessed by the Healthy Eating Index, the Alternate Healthy Eating Index, the Dietary Approaches to Stop Hypertension score, and health outcomes: a systematic review and meta-analysis of cohort studies.

Dietary patterns consider synergistic effects compared with isolated foods or nutrients on health outcomes. The aim of this systematic review and meta-analysis was to examine the associations of diet quality as assessed by the Healthy Eating Index (HEI), the Alternate Healthy Eating Index (AHEI), and the Dietary Approaches to Stop Hypertension (DASH) score and the risk of all-cause mortality, cardiovascular mortality or incidence, cancer mortality or incidence, type 2 diabetes mellitus, and neurodegenerative diseases. A literature search was performed using the electronic databases MEDLINE, SCOPUS, and EMBASE with an end date of May 10, 2014. Study-specific risk ratios were pooled using a random effect model by the Cochrane software package Review Manager 5.2. Fifteen cohort studies (34 reports), including 1,020,642 subjects, met the criteria and were included in the meta-analysis. Diets of the highest quality, as assessed by the HEI, AHEI, and DASH score, resulted in a significant risk reduction (RR) for all-cause mortality (RR 0.78, 95% CI 0.76 to 0.80; P<0.00001; I²=61%, 95% CI 20% to 81%), cardiovascular disease (incidence or mortality) (RR 0.78, 95% CI 0.75 to 0.81; P<0.00001; I²=45%, 95% CI 13% to 66%), cancer (incidence or mortality) (RR 0.85, 95% CI 0.82 to 0.88; P<0.00001; I²=77%, 95% CI 68% to 84%), and type 2 diabetes mellitus (RR 0.78, 95% CI 0.72 to 0.85; P<0.00001; I²=74%, 95% CI 52% to 86%). Differences observed for neurodegenerative diseases were not significant. Egger regression tests provided no evidence of publication bias. Diets that score highly on the HEI, AHEI, and DASH are associated with a significant reduction in the risk of all-cause mortality, cardiovascular disease, cancer, and type 2 diabetes mellitus by 22%, 22%, 15%, and 22%, respectively, and therefore is of high public health relevance.