Trends in Planetary Health Diet Index for the United States ( PHDI ‐ US ) Scores and Associations With Mortality Risk in the United States Between 1999 and 2020

This study utilized the Planetary Health Diet Index for the United States (PHDI‐US), a dietary index developed and validated for the U.S. population, to characterize temporal trends in PHDI‐US scores from 1999 to 2020, evaluate adherence to the EAT‐Lancet Planetary Health Diet, and examine associations between PHDI‐US scores and mortality risk. PHDI‐US scores were calculated using data from the National Health and Nutrition Examination Survey (NHANES) spanning 1999 to 2020, which encompassed a cohort of 55,579 adults ≥ 19 years of age living in the U.S. Total PHDI‐US scores can range between 0 and 150 and were derived from 24‐h dietary recalls. Weighted linear regression was used for trend analysis, and weighted Cox regression was employed to study mortality risk. Analysis of the aggregate dataset revealed a significant upward trend ( p ‐trend < 0.001) in PHDI‐US scores over the 21‐year period. Over this time, the average total PHDI‐US score for the overall U.S. population ranged between 41.2 and 46.5. This increasing trend was mirrored across various subpopulations, including age brackets, gender, race/ethnicity, poverty‐income ratios and educational levels. Higher scores (Q4 vs. Q1) were inversely associated with all‐cause mortality (HR = 0.78, 95% CI: 0.70–0.88, p < 0.001; consistent across all subgroups), cardiovascular mortality (HR = 0.77, 95% CI: 0.61–0.98; p = 0.034), and cerebrovascular mortality ( p ‐trend = 0.026). This study found a low total PHDI‐US score and a progressive escalation in scores among the American population between 1999 and 2020, a pattern also evident across all evaluated subgroups. In addition, an inverse association was discerned between PHDI‐US scores and mortality risk, indicating that elevated PHDI‐US scores might be concomitant with reduced mortality risk. This study has important public health implications for optimizing dietary patterns in the United States.