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 have 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 asthma 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 association between asthma-related hospital admissions and exposure to atmospheric particulates (PM10) and ozone (O3) using hospital discharge and air quality data for 1991-1994 for central Los Angeles. They used regression techniques with weighted moving averages (simulating distributed lag structures) to measure the effects of exposure on overall hospital admissions, admissions of uninsured patients, admissions for which MediCal (California Medicaid) was the primary payer, and admissions for which the primary payer was another government or private health insurance program.
RESULTS: No associations were found between asthma admissions and O3 exposure. An estimated increase from 1991 to 1994 of 50 micrograms per cubic meter in PM10 concentrations averaged over eight days was associated with an increase of 21.0% in the number of asthma admissions. An even stronger increase--27.4%--was noted among MediCal asthma admissions.
CONCLUSIONS: The authors conclude that low family income, as indicated by MediCal coverage, is a better predictor of asthma exacerbations associated with air pollution than lack of insurance and, by implication, a better predictor of insufficient access to primary care.