# Oxidative balance score and mortality: mediating role of insulin resistance across age strata in the NHANES cohort

## TL;DR

Higher oxidative balance scores are linked to lower mortality risk, especially in younger adults, with insulin resistance playing a mediating role.

## Contribution

This study innovatively shows that insulin resistance mediates the protective effect of oxidative balance scores on mortality in younger adults.

## Key findings

- Higher oxidative balance scores reduced all-cause and cardiovascular mortality risks.
- Insulin resistance indices mediated 17% of the protective effect in adults under 65 years.
- No mediation by insulin resistance was observed in adults aged 65 years or older.

## Abstract

This study examined the association between oxidative balance score (OBS), a composite measure of oxidative/antioxidative factors, and mortality, while investigating insulin resistance (IR) indices as potential mediators using a nationally representative cohort.

A cohort of 11,849 U. S. adults from NHANES (2007–2018) was analyzed. OBS integrated 16 dietary and 4 lifestyle components. Mortality risks (all-cause, cardiovascular, cancer) were assessed via weighted Cox models. Mediation analysis evaluated the indirect effects of five IR indices (TyG index, TG/HDL-C, HOMA-IR, eGDR, VAI) on OBS-mortality associations, with statistical validation of mediation effects. Analyses were stratified by age (<65 vs. ≥65 years) and adjusted for sociodemographic, behavioral, and clinical covariates.

Higher OBS reduced risks of all-cause (HR = 0.652, 95% CI: 0.525–0.81) and cardiovascular mortality (HR = 0.605, 95% CI: 0.408–0.898), but not cancer mortality. Innovatively, eGDR mediated 17% of OBS’s protective effect on all-cause mortality in adults <65 years, while TyG index and HOMA-IR showed weaker mediation. No IR mediation occurred in older adults (≥65 years).

Higher OBS levels were inversely associated with all-cause and cardiovascular mortality, partially mediated by insulin resistance pathways. These findings highlight OBS as a potential prognostic indicator for mortality risk.