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About Asthma data

About Asthma Data

Tracking asthma involves collecting data about the number of hospital or emergency room visits due to asthma.

This page provides general information about asthma data and measures developed by the Iowa Public Health Tracking program. Contact Us for more information about these data.

Information on this page:

What do these data tell us?

  • The numbers and rates of asthma hospitalizations and emergency department visits in Iowa by year, age group and gender.
  • If an asthma measure is going up or down over time.
  • If a segment of a population is at higher risk for hospitalization or a visit to the emergency department due to asthma.

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How can we use this data?

  • To inform the public about asthma hospitalizations and emergency department visits.
  • For program planning and evaluation by state and local partners.

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What can these data not tell us?

  • What causes asthma, or what leads to asthma hospitalizations and emergency department visits.
  • The total burden of asthma in a population.
  • The number of people who are hospitalized or who visited the emergency department due to asthma. Because personal identifiers are removed from the hospital discharge data before analysis, individuals who have multiple hospitalizations or emergency department visits cannot be identified.

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What is the source of the data?

  • Hospitalization and emergency department data are collected by the Iowa Hospital Association on behalf of IDPH in accordance with Iowa Code section 135.166.
  • Bridged-race population estimates from the National Center for Health Statistics and US Census. Data from 2000 to 2009 are based on intercensal population estimates and 2010-most current year are based on the postcensal population estimates.

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What time period of data is available?

  • The Iowa Public Health Tracking portal displays hospitalization data from the year 2000 through the most recent year of data available.
  • The Iowa Public Health Tracking portal displays Emergency Department visit data from the year 2003 through the most recent year of data available.
  • There is usually a two-year lag period before hospitalization and emergency department visit data are available.

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How are asthma hospitalizations and emergency department visits identified?

  • Hospitalizations are defined as Iowa residents who are discharged from a hospital in Iowa.
  • Emergency Department visits are defined as Iowa residents who are treated and released or subsequently admitted to a facility in Iowa.
  • Asthma hospitalizations have a primary discharge diagnosis of asthma.
  • Asthma emergency department visits have asthma as the first-listed diagnosis.
  • Asthma is defined as the International Classification of Disease 9th Revision, Clinical Modification (ICD-9-CM) codes that begin with 493.
  • Asthma is defined as the International Classification of Disease 10th Revision, Clinical Modification (ICD-10-CM) codes that begin with J44 or J45.

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What is the difference between a number, rate, age-adjusted rate, and age-specific rate? How would I use them?

Number:

  • If you want to understand the magnitude or how big the overall burden is, then use the number.
  • The number indicates the total number of hospitalizations or emergency department visits due to asthma, but not the number of unique individuals hospitalized or who visited the emergency department.
  • To protect an individual's privacy, counts of 5 or less are suppressed.

Crude Rate:

  • If you want to understand the probability or what is the underlying risk in a population, then use a rate.
  • In our analysis a rate is calculated using a numerator, the number of asthma hospitalizations during a period of time, divided by a denominator, the number of people in a population during the same period of time. This fraction is then multiplied by 10,000 to provide a more recognizable value.
  • To protect an individual's privacy, rates based on counts of 5 or less are suppressed.

Age-adjusted rate:

  • Age-adjusted rates are useful when comparing the rates of two population groups that have different age distributions.
  • A weighted average, called the direct method, is used to adjust for age in this analysis. Age specific rates in a given population are adjusted to the age distribution in a standard population by applying a weight. The U.S. 2000 Standard population is used as the basis for weight calculations.
  • To protect an individual's privacy, rates based on counts of 5 or less are suppressed.

Age-specific rate:

  • A rate of an event (such as disease or death) measured within a particular age group. It is similar to a crude rate but is calculated within an age group (e.g. an age-specific rate of asthma hospitalizations in adults 35-44 years of age).
  • To protect an individual's privacy, rates based on counts of 5 or less are suppressed.

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What are the limitations of the data?

  • Multiple hospitalizations or emergency department visits by the same patient cannot be identified, and are not excluded.
  • These data are not appropriate for estimating the total burden of asthma.
  • These measures use hospital admission dates while other public health programs use the hospital discharge dates to count asthma cases. This may cause a difference in asthma rates between the Tracking Network and other public health websites.
  • Iowa residents discharged from hospitals in surrounding states are not included, so hospitalization and emergency department visit rates for counties in which residents are likely to receive care in a surrounding state may be underestimated. Rates for counties in which residents are likely to visit hospitals that do not submit data to the Iowa Hospital Association (e.g., Veteran's Administration, Indian Health Services hospitals, and institutionalized populations) may also be artificially low.
  • There is usually a two-year lag period before hospitalization and emergency department visit data are available.

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Where can I find more technical information about the data?

More detailed documentation of the asthma hospitalization and emergency department visit data can be found in the following documents:

Indicator Profiles

Emergency Department Visits for Asthma pdf
Hospitalizations for Asthma pdf

Descriptive Metadata

Emergency Department Visits for Asthma pdf
Hospitalizations for Asthma pdf

Contact Us to learn more about asthma, hospitalization and emergency department visit data, or any of the measures displayed on the Iowa Public Health Tracking Portal.

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