Outcome definition and index validity in cross-national comparisons of diet-attributable metabolic burden
- 1Ningbo City College of Vocational Technology
Abstract
BackgroundIn three national surveys, no cross-national ranking of diet-attributable metabolic burden was identified: the apparent ordering moved with the definition of the outcome and with the validity of the dietary index. Both were tested.
Subjects/MethodsWe harmonised individual-participant data from national surveys in the USA (NHANES 2017-2018), Korea (KNHANES 2015-2021) and Mexico (ENSANUT 2018-2019); 56,365 adults in total, recovered Mexican blood-pressure data from the raw files, and defined metabolic syndrome (MetS) with a common five-component ATP III rule. We estimated survey-weighted sex-specific associations of the energy-adjusted Dietary Inflammatory Index (E-DII) with MetS, country-specific population-attributable fractions (PAFs) on a common counterfactual scale, and the E-DIIs correlation with log high-sensitivity C-reactive protein (hsCRP). A quantitative bias analysis examined whether validity differences could reverse the country ordering.
ResultsThe E-DII-MetS association was larger in women (USA OR 1.23, 95% CI 0.98-1.55; Korea 1.078, 1.028-1.132; Mexico 1.074, 0.992-1.163; interaction P=0.080) but disappeared without blood pressure in the outcome (pooled 1.065, 0.982-1.155; P=0.13). Female PAFs were 15.0%, 7.6% and 3.8%; no pairwise difference was distinguishable (all P[≥]0.23). E-DII validity was 0.137 in US women versus 0.040 in Korean women (P=2.0x10-4); the validity ratio was 0.29, correction reversed the observed ordering, and its interval straddled the reversal threshold.
ConclusionsNeither the direction nor the magnitude of cross-national differences in diet-attributable MetS burden was identified; the ordering was bounded by outcome definition and by index validity. Cross-national burden comparisons require local validation of both.
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BibTeX
@misc{huang2026outcome,
title = {{Outcome definition and index validity in cross-national comparisons of diet-attributable metabolic burden}},
author = {S. Huang and X. Wang},
howpublished = {medRxiv},
year = {2026},
month = jul,
doi = {10.64898/2026.07.25.26358918},
url = {https://www.medrxiv.org/content/10.64898/2026.07.25.26358918v3},
note = {CC BY-NC},
}
RIS
TY - UNPB
TI - Outcome definition and index validity in cross-national comparisons of diet-attributable metabolic burden
AU - S. Huang
AU - X. Wang
PY - 2026
DA - 2026/07/25
PB - medRxiv
DO - 10.64898/2026.07.25.26358918
UR - https://www.medrxiv.org/content/10.64898/2026.07.25.26358918v3
AB - BackgroundIn three national surveys, no cross-national ranking of diet-attributable metabolic burden was identified: the apparent ordering moved with the definition of the outcome and with the validity of the dietary index. Both were tested. Subjects/MethodsWe harmonised individual-participant data from national surveys in the USA (NHANES 2017-2018), Korea (KNHANES 2015-2021) and Mexico (ENSANUT 2018-2019); 56,365 adults in total, recovered Mexican blood-pressure data from the raw files, and defined metabolic syndrome (MetS) with a common five-component ATP III rule. We estimated survey-weighted sex-specific associations of the energy-adjusted Dietary Inflammatory Index (E-DII) with MetS, country-specific population-attributable fractions (PAFs) on a common counterfactual scale, and the E-DIIs correlation with log high-sensitivity C-reactive protein (hsCRP). A quantitative bias analysis examined whether validity differences could reverse the country ordering. ResultsThe E-DII-MetS association was larger in women (USA OR 1.23, 95% CI 0.98-1.55; Korea 1.078, 1.028-1.132; Mexico 1.074, 0.992-1.163; interaction P=0.080) but disappeared without blood pressure in the outcome (pooled 1.065, 0.982-1.155; P=0.13). Female PAFs were 15.0%, 7.6% and 3.8%; no pairwise difference was distinguishable (all P[≥]0.23). E-DII validity was 0.137 in US women versus 0.040 in Korean women (P=2.0x10-4); the validity ratio was 0.29, correction reversed the observed ordering, and its interval straddled the reversal threshold. ConclusionsNeither the direction nor the magnitude of cross-national differences in diet-attributable MetS burden was identified; the ordering was bounded by outcome definition and by index validity. Cross-national burden comparisons require local validation of both.
ER -