Jeffrey Johnson, MPH; Annie Kao, MPH, MSc; Louise Gresham, PhD, MPH; Michele Ginsberg, MD
San Diego County Health & Human Services Agency, San Diego, CAThis paper describes the use of Geographic Information Systems (GIS) in the analysis and of severe asthma cases in San Diego County. This descriptive epidemiologic study utilizes mortality and hospitalization data to characterize the profiles and geographic variation of the population affected by asthma. It also demonstrates how GIS can be used to integrate environmental and social data that may be closely associated with specific asthma health outcomes. These results can aid in assessing the etiology of asthma across a diverse population. In addition, this paper seeks to highlight some important regional or population groups that may benefit from asthma intervention and prevention efforts.
Asthma is one of the most common chronic diseases in the United States and has increased in prevalence nationally over the past two decades. It is a disease resulting from airway inflammation and airway limitation. An asthma attack can include coughing, chest tightness, wheezing, and difficulty breathing. Although the actual cause of asthma is not known, asthma attacks can be triggered by a variety of allergens or irritants.
This descriptive epidemiologic study utilizes mortality and hospitalization data to characterize the population severely affected by asthma in San Diego County. It also demonstrates how GIS can be used to assess the geographic distribution of cases and to integrate environmental and social information that may be closely associated with specific asthma health outcomes. This study will result in several hypotheses that might be useful for future study. In addition, this paper seeks to highlight some important regional or population groups that may benefit from asthma intervention and prevention efforts.
The data sources used to describe severe asthma among San Diego County residents include death data, hospital discharge data and population estimates from San Diego Association of Governments (SANDAG). All deaths occurring among San Diego County residents between 1994 and 1998 were included in this study if an underlying cause of death for asthma (ICD-9 493) was listed on the death certificate. Likewise, all hospital discharges among San Diego County residents during 1997 and 1998 with a primary diagnosis of asthma (ICD-9 493) were selected. Mortality and hospitalization rates were calculated using yearly San Diego County population estimates and were adjusted to the 1940 U.S. standard population.
The data were analyzed by selected characteristics including age, race, sex, hospital costs, and source of payment type. In addition, the deaths and hospitalizations were analyzed for geographic characteristics using ArcView 3.1. Traditional epidemiological markers for asthma including information about age of houses, major freeways, income and poverty levels in San Diego County were also considered in relation to the geographic distribution of cases. The geographic unit of analysis included six Health Service Regions and zipcode areas.
This study demonstrates that there are demographic and geographic variations of asthma mortality and hospitalizations among residents of San Diego County particularly among residents of Central Service Region. Although the actual causes of asthma cannot be determined by this study, many hypotheses have been generated for future study areas. Although there are known limitations with the data sources and these results are not indicators of asthma prevalence, these results can aid in assessing the etiology of asthma across a diverse population. Geographic Information Systems (GIS) are a useful tool for epidemiologists describing the epidemiology of asthma, and may play a role in asthma surveillance systems. Collecting local asthma data may prove useful in assessing the etiology of asthma and for planning and evaluating public health prevention programs, most notably among the high risk groups and geographic regions identified in this study.