Effect of insurance coverage on the relationship between asthma hospitalizations and exposure to air pollution

Objective. Based on the assumption that people without health insurance hav e limited access to the primary care services needed to prevent unnecessary hospitalizations for asthma, the authors hypothesized that insurance is a factor in the strength of the association between hospital admissions for a sthma and exposure to air pollution, They tested this hypothesis with 1991- 1994 data from central Los Angeles. Methods. The authors analyzed the effect of insurance status on the associa tion between asthma-related hospital admissions and exposure to atmospheric particulates (PM10) and ozone (O-3) using hospital discharge and air quali ty data for 1991-1994 for central Los Angeles. They used regression techniq ues with weighted moving averages (simulating distributed lag structures) t o measure the effects of exposure on overall hospital admissions, admission s of uninsured patients, admissions for which MediCal (California Medicaid) was the primary payer, and admissions for which the primary payer was anot her government or private health insurance program. Results. No associations were found between asthma admissions and O-3 expos ure. An estimated increase from 1991 to 1994 of 50 micrograms per cubic met er in PM10 concentrations averaged over eight days was associated with an i ncrease of 21.0% in the number of asthma admissions. An even stronger incre ase-27.4%-was noted among MediCal asthma admissions. Conclusions. The authors conclude that low family income, as indicated by M ediCal coverage, is a better predictor of asthma exacerbations associated w ith air pollution than lack of insurance and, by implication, a better pred ictor of insufficient access to primary care.