Baseline Food Supply-Based Dietary Scores and Ischemic Heart Disease Mortality: A Longitudinal Cross-Country Study

Background/Objectives: National food environments may be associated with cardiovascular risk, but how their association with country-level ischemic heart disease (IHD) mortality differs across diet-quality indices remains unclear. We compared six food supply-based dietary scores calculated using 2010 food data in relation to annual IHD mortality from 2010 to 2021. Methods: We conducted a longitudinal study of 148 countries with populations ≥ 1 million. Using 2010 FAOSTAT Food Balance Sheet data, we calculated the Dietary Approaches to Stop Hypertension (DASH) score, the Alternative Healthy Eating Index (AHEI), Mediterranean Diet Score (MDS), Traditional Japanese Diet Score (TJDS), Planetary Health Diet Index (PHDI), and Quantitative Index for Dietary Diversity (QUANTIDD). The outcome was age-standardized IHD mortality during 2010–2021. Associations between time-invariant baseline dietary scores and annual IHD mortality were assessed using multivariable-adjusted linear mixed-effects models. Effect sizes were expressed as mortality rate ratios (MRRs) per 1-standard deviation (SD) higher score; model fit was compared using Akaike information criterion (AIC) weights and marginal R2, and effect estimates were compared pairwise. Results: Higher DASH and AHEI scores were associated with lower IHD mortality. MRRs per 1-SD higher score were 0.914 (95% confidence interval, 0.849–0.983) for DASH and 0.908 (95% confidence interval, 0.838–0.985) for AHEI. No significant associations were observed for MDS, TJDS, PHDI, or QUANTIDD. DASH had the highest AIC weight (0.434), followed by AHEI (0.341), with a slightly higher marginal R2 for DASH. Pairwise comparisons showed no statistically significant differences in effect estimates between DASH and AHEI or between either of these scores and the other dietary scores. Conclusions: Higher baseline DASH and AHEI scores were associated with lower IHD mortality during 2010–2021, with similar effect estimates per 1-SD higher score and broadly comparable model fit. However, direct pairwise comparisons revealed no statistically significant differences in standardized effect sizes between these scores (DASH and AHEI) and the other dietary scores. These findings suggest that the relevance of dietary scores may depend on the outcome and analytic context rather than the superiority of a single index. Because this was an ecological study, these findings should not be interpreted as individual-level causal effects.