Background. Convincing evidence now exists that particulate air pollution exacerbates heart and lung disease, leading to increased morbidity and mortality. The populations particularly susceptible to these exposures are still unclear. Recent work on potential mechanisms of action of particulate air pollution point to pathways also influenced by diabetes.
Methods. We examined effect modification by concurrent diagnosis of diabetes overall and by age group in a hierarchical model for four U.S. cities. In the first stage, separate Poisson regressions were fit in each city and within each stratum of age and diabetes. In the second stage, the estimated effect size for PM10 (particulate air matter with aerodynamic diameter less than 10 microns) within city and strata was regressed against the stratification variables, allowing for a random effect. We used Medicare data for Chicago, IL, Detroit, MI, Pittsburgh, PA, and Seattle, WA, for the years 1988-1994.
Results. We found that diabetics have double the risk of a PM10-associated cardiovascular admission compared with nondiabetics. We also found that persons 75 years of age and older had higher risk, and that the interaction between the two categories (diabetes and age) was less than additive. If the latter is confirmed, it may represent a survivor effect among diabetes, enhanced susceptibility among nondiabetics, or both.
Conclusions. We conclude that diabetics are a population that is particularly susceptible to cardiovascular damage by airborne particles.