Spatial variation of asthma rates in Los Angeles County by environmental and socioeconomic indicators

BACKGROUND: Asthma is a chronic lung disease affecting nearly 1.2 million people in Los Angeles (LA) County. Asthma can be triggered and worsened by environmental pollutants. Exposure to oil/gas well operations, environmental contamination, and other forms of environmental degradation have been linked with poorer respiratory outcomes. METHODS: We used Generalized Additive Models (GAMs) with a bivariate smooth of location and Quasipoisson framework to examine the relationship between location and asthma emergency department visitation (EDV) rates for census tracts in LA County (n = 2106). Using CalEnviroScreen scores, we predicted and mapped the rates after adjustment for environmental exposures and socioeconomic factors to determine if observed spatial patterns in asthma EDV could be explained by these known characteristics. Permutation tests were conducted to identify areas of elevated asthma EDV rates. We also calculated rate ratios (RR) and 95% confidence intervals for the indicators. RESULTS: The rate of asthma EDVs was highest to the north of the major shipping ports in the county. Per interquartile range increase, poverty (RR: 1.29 [1.26–1.32]), percent of the population unemployed (RR: 1.02 [1.00–1.03], and solid waste site scores (RR: 1.01 [1.00–1.02]), were associated with higher asthma EDV rates. Poverty contributed the most to the observed spatial variation in asthma EDV. CONCLUSION: These findings can motivate future research to investigate spatial variation in asthma using higher resolution individual-level data, especially in the identified areas of elevated risk in LA County. Solid waste exposure indicators, poverty level, and unemployment explained some of the spatial variation of asthma EDV rates. Closer investigations in these geographic areas can help us better understand the disparities in exposure and risk.