Air pollution-associated changes in biomarkers of diabetes risk

Ambient particulate matter (PM) and nitrogen oxide (NO_x) air pollution may be diabetogenic.

To examine longitudinal associations of short- and longer-term mean PM ≤10 microm (PM₁₀), PM ≤2.5 microm (PM_2.5), and NO_x concentrations with five biomarkers of diabetes risk.

We studied a stratified, random minority oversample of nondiabetic Women's Health Initiative clinical trials participants with biomarkers and geocoded participant address-specific mean air pollution concentrations available at repeated visits (years = 1993-2004; n = 3,915; mean age = 62.7 years; 84% white). We log-transformed the biomarkers, then used multi-level, mixed-effects, longitudinal models weighted for sampling design/attrition and adjusted for sociodemographic, clinical, and meteorological covariates to estimate their associations with air pollutants.

Biomarkers exhibited null to suggestively negative associations with short- and longer-term PM₁₀ and NO_x concentrations, e.g., -3.1% (-6.1%, 0.1%), lower homeostatic model assessment of insulin resistance per 10 microg/m³ increase in 12-month PM₁₀. A statistically significant interaction by impaired fasting glucose (IFG) at baseline in this analysis indicated potentially adverse effects only among women with versus without IFG, i.e., 1.4% (-3.5%, 6.5%) versus -4.6% (-7.9%, -1.1%), P _interaction < 0.05. In contrast, longer-term PM_2.5 concentrations were largely but not statistically significantly associated with higher biomarkers.

Low-level short-term PM₁₀ and NO_x concentrations may have negligible adverse effects on biomarkers of diabetes risk. Although longer-term mean PM_2.5 concentrations showed primarily null associations with these biomarkers, results suggestively indicated that PM_2.5 exposure over the range of concentrations experienced in the United States may adversely affect biomarkers of diabetes risk at the population level, as may longer-term mean PM₁₀ concentrations among women with IFG.