Long-term exposure to ambient air pollutant mixture and metabolic obesity phenotypes: Results from a nationwide Korean study (2007-2019).

Background: Academic interest in the health impacts of air pollutant mixtures has increased in past years. Studies indicated that air pollutants exposure is linked to obesity and metabolic syndrome.

Objective: This study aimed to explore the association of air pollutant mixture with metabolic obesity phenotypes.

Methods: A nationwide sample of 68,675 adults was analyzed in our cross-sectional study. Participants were linked to modeled air pollution data from 2007 to 2019. The concentrations of PM_2.5-10, PM_2.5, NO₂, CO, SO₂, and O₃ were estimated for 2-year moving averages. Metabolic obesity phenotypes were classified into metabolically healthy obesity (MHO; body mass index [BMI] ≥25 kg/m²; without metabolic abnormality) and metabolically unhealthy obesity (MUO; BMI ≥25 kg/m²; with metabolic abnormality). The quantile g-computation was used to determine the association of air pollutant mixture with MHO and MOU.

Results: In total, 46,061 individuals were classified as non-obese, 2724 individuals were classified as MHO, and 19,890 individuals were classified as MUO. In the quantile g-computation, one quartile increase in the concentration of air pollutant mixture was positively associated with MUO (OR [odds ratio]: 1.12, 95% CI [confidence interval]: 1.05-1.19) but not with MHO (OR: 1.00, 95% CI: 0.87-1.15). O₃, CO, and PM_2.5-10 accounted for 37.6%, 21.6%, and 21.3% of the positive association of air pollutant mixture with MUO, respectively.

Impact: Mounting evidence shows that outdoor air pollution is linked to obesity. We explored the association between long-term exposure to air pollutant mixture and metabolic obesity phenotypes. Obesity phenotypes were classified as metabolically healthy obesity (MHO) and metabolically unhealthy obesity (MUO). A mixture analysis showed that quartile increase in the concentration of the air pollutant mixture is associated with 1.12-fold increase in the odds of MUO, but not with MHO. Our novel findings suggest that long-term exposure to air pollutants may affect both metabolic abnormalities and obesity, contributing to a shift towards a metabolically unfavorable obesity profile.