Underlying Cause of Death (UCD) Data


Wide-ranging Online Data for Epidemiologic Research (WONDER) — is an easy-to-use internet system that makes the information resources of the Centers for Disease Control and Prevention (CDC) available to public health professionals and the public at large. It provides access to a wide array of public health information.

CDC WONDER furthers CDC’s mission of health promotion and disease prevention by speeding and simplifying access to public health information for state and local health departments, the Public Health Service, and the academic public health community. CDC WONDER is valuable in public health research, decision making, priority setting, program evaluation, and resource allocation.  To learn more about WONDER go to: https://wonder.cdc.gov/wonder/help/faq.html#1.

Uses for Asthma Surveillance

Several questions can be addressed statewide using CDC/WONDER underlying cause of death (UCD) mortality data:

Q What is the rate of deaths where asthma is the underlying cause?

Q Is the asthma mortality rate higher than the national average or the Healthy People 2020 (HP2020) objectives?

Q Does asthma mortality vary by age, sex, race, or geography or a combination of these?

Q What are the yearly trends in deaths with asthma as the underlying cause?

History of UCD Mortality Data Collection

Mortality data are complied at the federal level using the National Vital Statistics System (https://www.cdc.gov/nchs/about/major/dvs/desc.htm).

The collection of death data in the United States is undertaken in a uniform manner and is based upon the U.S. Standard Certificate of Death and the U.S. Standard Report of Fetal Death, which are issued by the Public Health Service.  States have the flexibility to modify these forms to meet particular needs or to comply with specific laws.  However, the death certificates used by most states closely conform to the standard forms in both content and arrangement of elements.  Cause-of-death statistics can be based on the Underlying Cause of Death (UCD), which is defined as (a) the disease or injury which initiated the chain of events leading directly to death, or (b) the circumstances of the accident or violence which produced the fatal injury (United States Public Health Service 1994).

Deaths are coded based on the applicable revisions of the International Classification of Diseases (ICD), which is published by the World Health Organization (WHO, 1997).  From 1979-1998, deaths have been coded under ICD Revision 9 (ICD-9).  The ICD-9 codes for asthma are 493.x (where x = blank, 0, 1, 2, or 9). When using ICD-9 coding, be sure to determine how the system treats the field after the decimal.  In many applications, a blank following the decimal is counted separately from a zero following the decimal (i.e., 493. is not equal to 493.0). The current version of WONDER gives the same results using 493 – 493 as it does for 493 – 493.9 or 493.0 – 493.9.

As a practical matter, asthma deaths are seldom reported in statistical tabulations using the decimal subclassifications, and any ICD 493 Code (i.e., 493.x, where x = blank, 0, 1, 2, or 9) is considered an asthma death.

Coding terminology for asthma, as well as other illnesses, has changed with ICD Revision 10 (ICD-10), which began in 1999 (WHO, 1992).  In ICD-10, asthma is coded as J45.x – J 46.x (where x = blank, 0, 1, 8, or 9).  The National Center for Health Statistics (NCHS) reports a comparability ratio of 0.8938 for the coding of asthma mortality under ICD-10 as compared to ICD-9.  That is, about 11% fewer deaths will be coded as indicated that asthma was the UCD compared to those deaths coded under ICD-9.  To calculate comparability ratios for your state, go to https://www.cdc.gov/nchs/data/statab/Document%20for%20the%20States.pdfpdf icon  for a copy of “A Guide to State Implementation of ICD-10 for Mortality” parts I and II, for instructions.

How to Access CDC/ WONDER Data

  • Use your Internet browser to go to https://wonder.cdc.gov
  • Under the heading “Mortality” click on “Compressed Mortality” or Detailed Mortality.”
  • Click on either “Mortality for 1979 – 1998 with ICD 9 codes” or “Mortality for 1999 – 2015 with ICD 10 codes.”

The following page contains a tutorial designed to walk one through retrieving data from the CDC/WONDER site.  In this example, age-adjusted asthma death rates can be obtained by race for persons ≥ 5 years old for the period 1979 – 1998.  While CDC/ WONDER can be used to obtain crude and age-adjusted death rates by a variety of additional characteristics, this example is intended to provide enough familiarity to undertake additional analyses independently.

Direct your Internet browser to https://wonder.cdc.gov.  Make sure pop-ups are allowed.

  • At the Welcome to CDC/ WONDER screen, under the heading ““Mortality” Click on “Detailed Mortality” and the data use agreement will appear.
  • Agree to the data use agreement.
  • The Underlying Cause of Death 1999-2015 Request screen will appear

Use the following steps to complete each area of this screen.

  1. Organize table layout:
    • Select groupings:
      Select how you would like to summarize your data.  You may choose multiple groupings.
    • Select Measures:
      Select the measures you would like to have summarized in the output.  Default measures will automatically be checked: Deaths Population Crude
      Rate. Select age-adjusted rate.
    • Additional Rate Options:
    • Calculates rates per:
      Select 1,000,000
    • Select Standard Population:
      Highlight 2000 U.S. Standard Population
      Or, Non-Standard Population:
      Leave unchecked (following the recommendations of the NCHS https://www.cdc.gov/nchs/data/statnt/statnt20.pdfpdf icon)
  2. Select location:
    • Select State, Census Region or HHS Region:
      Select the state to be queried from the list of states.
  3. Select demographics:
    • Select age, gender, Hispanic origin, and race:
      Select the desired demographics of interest.
  4. Select age ranges:
    • Age may be presented in Ten-Year Age Groups, Five-Year Age Groups, Single-Year Age and Infant Age Groups.
      To select 0-18 years, click on Single-Year Age and in the box, highlight “<1year” – “18 years.”
  5. Select gender:
    Leave set at “All.”
  6. Select Hispanic Origin:
    Leave set at “All.”
  7. Select race:
    Leave set at “All.”
  8. Select year:
    • Select years:
      Highlight desired year(s).
  9. Select weekday, autopsy or place of death:
    • Select weekday:
      Leave set at “All weekdays.”
    • Select autopsy
      Leave set at “All values.”
    • Select place of death:
      Leave set at “All places.”
  10. Select Cause of Death
    • To search ICD code ranges:
      • Click on “ICD-10 codes.” In the box below, select “search.” In the box, type “asthma.”  When the list appears, select J45 through J46 (highlight the codes).  Once all six are highlighted, they will appear in the box on the right.
    • Other Options
      • Select “Show Suppressed Values”

    Click “Send.”  The results of your query will appear in another window.

    More detailed instructions and background for those who wish to query the Compressed Mortality Data can be found at https://wonder.cdc.gov/wonder/help/main.html or by clicking the link “Compressed Mortality data description.”

    Additional Queries

    Additional queries can be generated by repeatedly modifying the indicators in various steps of the Underlying Cause of Death 1999-2011 Request Screen.  By manipulating the region, age, gender, and race fields in the appropriate steps, the data set queried can be limited in order to conduct analysis within specific demographic, geographic, or temporal specifications.  By manipulating the fields in step 7, crude or adjusted death rates can be compared between categories of age, race, gender, year, ICD-10 code, or county of residence.

    Analysis Standards

    Standard demographic breakdowns may be used when analyzing asthma surveillance data.  The applicability of these breakdowns to CDC/WONDER UCD data is summarized below.

    • Age Categories: Rates can be calculated by age for single year, 5-year 10-year, and infant age intervals for groups
    • Sex Categories: Rates can calculated separately for “Male” and “Female” categories.
    • Race Categories: Rates can be calculated separately for “White,” “Black,” and “Other” categories.  The “Other” category includes American Indian or Alaska Native and Asian or Pacific Islander.
    • Hispanic Origin
    • Hispanic Origin can also be identified. It can be combined with the race categories or it can be a mutually exclusive category.
    • Time Trends: Rates can calculated by year if the cell size permits.
    • Geographic Categories: Rates can be calculated at the state and county level if the cell sizes permit. Age standardized rates should be used to compare geographic units.

    NOTE:  Small sample size can result in release or inferred release of confidential or sensitive information and can also affect reliability of rates.  Please consider collapsing years or demographic groups, presenting confidence intervals, and/or suppressing rates and counts if sample size of the numerator or denominator is inadequate.  In some cases, an aggregation of categories of data may be necessary to achieve the relative standard error of 23% that has been suggested to produce reliable rates (https://www.cdc.gov/nchs/data/statnt/statnt24.pdfpdf icon).  For example, if the event count is <20 in any particular year, we recommend combining years to achieve numerators ≥20, and/or estimating trends based on 3-year rolling averages (e.g., calculate a single rate for 1978-1980, then 1979-1981, etc.).  To protect patient confidentially, we recommend that counts <10 cases be suppressed.

    National Indicators

    Mortality due to asthma is included in the HP2020 objectives.  These objectives use deaths with an underlying cause of asthma (ICD-9 Code 493.x, where x = blank, 0, 1, 2, or 9; ICD-10 Code J45.x – J46.x where x = blank, 0, 1, 8, or 9) for the numerator and resident population from the U.S. Census for the denominator.

    HP2020 Objective RD-1:  Reduce asthma deaths to:

    • 9/1,000,000 in adults 35-64 years of age (RD-1.2)
    • 5/1,000,000 in persons 65 years of age and older (RD-1.3)

    National Comparison Data Source:  National Vital Statistics System (NVSS), CDC, NCHS.

    Anticipated Questions and Answers

    Q Shouldn’t states use their own vital statistics data services instead of CDC/WONDER?

    A The use of CDC/WONDER will facilitate standardization and comparability of rates across states, as each state will make use of a common approach to age-adjustment, and a common source of denominator data.  However, states may want to produce asthma death rates using their own vital statistics data (e.g., in order to look at deaths for smaller geographic regions within their state).  In these cases we encourage states to make use of July 1 state resident population estimates for each year (not including armed forces overseas) as denominators to maintain comparability of rates across states.  These data can be downloaded from the U.S. Census Bureau web site at http://www.census.gov/popest/estimates.php.

    Q Is mortality a good indicator of the burden of asthma?

    A Publication of mortality data does not replace the need for estimation of asthma prevalence and health care utilization as indicators of disease burden.

    Q Are deaths that occur out of the state of residence linked back to that state?

    A Deaths are assigned to the decedent’s state of residence as determined by the person completing the death certificate.


    Federal and State Contacts and Resources for UCD Mortality Data

    Centers for Disease Control and Prevention Contacts (CDC)
    National Center for Environmental Health
    Asthma and Community Health Branch
    General Number: (770) 488-3700
    Current state asthma contacts:  http://www.cdc.gov/asthma/contacts/default.htm

    General Contact Number: 1-800-496-8347

    National Center for Health Statistics
    Division of Vital Statistics
    General Number:  1-800-232-4636



    1. United States Public Health Service. Vital Statistics of the United States, 1990. Vol. II:  Mortality, Part A.  Technical Appendix.  Washington, DC:  US Government Printing Office; 1994.  DHHS publication no. (PHS) 95-1101.
    2. World Health Organization. Manual of the International Statistical Classification of Diseases, Injuries, and Causes of Death:  9th Geneva. 1977.
    3. World Health Organization. International Statistical Classification of Diseases and Related Health Problems:  10th Geneva. 1992.
    4. Healthy People 2020 is available at http://www.health.gov/healthypeople/external icon
Page last reviewed: May 14, 2019