What is asthma?

Asthma is a disease characterized by ongoing inflammation that takes place in the lining of the lung passages.  Frequently, this inflammation does not cause symptoms.  Other times, the lung passages undergo spasms resulting in coughing, chest tightness, and wheezing.  This is known as an "asthma attack". 

Symptoms may be mild and go unnoticed for long periods of time.  Other times they may interfere with school, work, or play.  For some, attacks may be serious enough to warrant visits to the emergency room or stays in the hospital overnight or longer.  In the worst situations, death can occur.  About 400 to 500 children die from asthma each year in the United States.  Asthma is the most common chronic disease among children in this country. 

Evidence suggests that asthma is fundamentally a problem with how the body's immune system is regulated.  Asthma attacks are noted to be triggered by environmental phenomena such as the weather, tobacco smoke, mold, dust, cockroaches, or pollution.  Although there is no known cure for asthma, many children outgrow their disease, and severe attacks are generally considered preventable.  With access to quality care, the use of relatively simple medications, and avoidance of asthma triggers, asthma can be fully managed.  

Assessing asthma among populations

Unlike preterm birth or low birthweight, the question of how much asthma there is in a population is difficult to answer because there is no single definitive way of measuring asthma.  Asthma can be diagnosed by physicians over time through interviews with patients, physical examinations, trials of medications, and laboratory lung function testing.  However, some individuals with asthma may not be diagnosed, especially if they are not receiving adequate medical care. 

Researchers who are interested in examining asthma in a population may use a number of different methods.  For example, some may use data collected by school districts or through phone surveys to estimate the amount of asthma among a group of people.  Others may measure asthma indirectly by studying its impact on work, school attendance, or the health care system.  These different ways of measuring asthma each have their benefits and drawbacks.

One commonly used measure is the rate of hospitalizations due to asthma.  All hospitals in California must report this information to the state.  One of the benefits of this measure is that we have information about hospitalizations from asthma for the entire state population.  However, there is a major caution against using asthma hospitalization rates to represent the overall asthma rate.  Hospitalizations from asthma represent the most severe asthma attacks, which are generally preventable with ongoing medications and avoidance of triggers.  Therefore, these hospitalizations reflect asthma among the people with the most severe disease and among those without access to high quality health care that might otherwise prevent these severe attacks.  Individuals with less severe asthma or better health care are unlikely to be counted in this measure.

The best way to get a more complete picture of asthma in a population is to look at a variety of measures, or indicators, of asthma.         

Asthma analysis

In this project, we examined a spectrum of asthma indicators for a large sample of Alameda County residents in 2001 using data from Medi-Cal fee-for-service and Kaiser Permanente of Northern California.  

We looked at rates of Emergency Room (ER) visits due to asthma, which is a similar measure to asthma hospitalization rates in that they reflect people with severe and/or poorly cared-for disease.  We also looked at rates of standard "check-up" (or outpatient) visits to the clinic/physician, as well as rates of asthma medication purchases.  These indicators reflect people whose asthma is well-cared for. 

For example, high quality healthcare would ensure that an individual is diagnosed with asthma by his or her physician, have regular outpatient visits, and be prescribed the appropriate asthma medications.  On the other hand, an individual with worse healthcare may not be diagnosed with asthma, may not see a clinician for regular preventative or maintenance visits, may not be prescribed medication, or may not be given appropriate education and guidance on how to prevent asthma attacks.  The management of asthma through medication use and avoidance of asthma triggers can prevent severe asthma outcomes such as ER visits, hospitalizations, or death.

By examining these various indicators of asthma, we hoped to understand asthma rates for residents of Alameda County across a spectrum of disease severity, health care access, and socioeconomic status.  Figure 1 illustrates these indicators along a spectrum of severity and quality of care.  

Figure 1. Spectrum of asthma indicators

Through the pilot project, we calculated the rates of ER visits, outpatient visits, symptom medication purchases, and maintenance medication purchases for Alameda County in 2001.  We created maps for each of the indicators and also examined if there were differences in which outcome occurred based on median income.  Additionally, we used these rates to estimate and map the total direct cost of the four asthma outcomes throughout the county. 

Click below to see asthma outcomes findings:

Asthma disparities

Asthma maps and tables

Mapping the cost of asthma

See Associations Findings on traffic pollution and asthma

Questions about asthma or these results?  Click below:

FAQs on asthma and results

Overview of pilot project data and methods

Additional Resources on asthma

For questions or more information, please contact:

Michelle Wong

Health Educator

mwong@dhs.ca.gov

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