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

Background Suboptimal diet quality has a large impact on noncommunicable disease burden. Objective This study aimed to update the body of evidence on the associations between diet quality, as assessed by the Healthy Eating Index, Alternate Healthy Eating Index, and the Dietary Approaches to Stop Hypertension score, and health status. Moreover, results of the previous systematic reviews and meta-analyses were extended by evaluating the credibility of the evidence. Methods PubMed, Embase, and Scopus databases were searched to identify eligible studies published between May 15, 2017 and March 14, 2020. Pooled relative risk (RR) with 95% CI for highest vs lowest category of diet quality were estimated using a random-effects model. Heterogeneity was explored using Cochran's Q test and I-2 statistic with 95% CI. Presence of publication bias was detected by using funnel plots and Egger's regression test. The NutriGrade tool was used to assess the credibility of evidence. Results The current update identified 47 new reports, resulting in a total of 113 reports including data from 3,277,684 participants. Diets of the highest quality, as assessed by the Healthy Eating Index, Alternate Healthy Eating Index, and Dietary Approaches to Stop Hypertension scores, were inversely associated with risk of all-cause mortality (RR 0.80, 95% CI 0.79 to 0.82, I-2 = 68%, n = 23), cardiovascular disease incidence or mortality (RR 0.80, 95% CI 0.78 to 0.82, I-2 = 59%, n = 45), cancer incidence or mortality (RR 0.86, 95% CI 0.84 to 0.89, I-2 = 73%, n = 45), incidence of type 2 diabetes (RR 0.81, 95% CI 0.78 to 0.85, I-2 = 76%, n = 16), and incidence of neurodegenerative diseases (RR 0.82, 95% CI 0.75 to 0.89, I-2 = 71%, n = 12). In cancer survivors, the highest diet quality was linked with lower risk of all-cause (RR 0.83, 95% CI 0.77 to 0.88, I-2 = 45%, n = 12) and cancer mortality (RR 0.82, 95% CI 0.75 to 0.89, I-2 = 44%, n = 12). The credibility of evidence for identified associations between overall healthy dietary patterns and included health outcomes was moderate. Conclusion This updated systematic review and meta-analysis suggests that high diet quality (assessed by the Healthy Eating Index, Alternate Healthy Eating Index, and Dietary Approaches to Stop Hypertension) is inversely associated with risk of all-cause mortality, cardiovascular disease incidence or mortality, cancer incidence or mortality, type 2 diabetes, and neurodegenerative disease, as well as all-cause mortality and cancer mortality among cancer survivors. Moderate credibility of evidence for identified associations complements the recent 2020 Dietary Guidelines Advisory Committee report recommending healthy dietary patterns for disease prevention.