About ZIP Code Asthma Emergency Department Visit Rates by County and ZIP Code
Asthma Emergency Department (ED) data generated from two databases within the Statewide Planning and Research Cooperative System (SPARCS): the (1) Hospital Inpatient database and (2) Outpatient database were used to create ZIP code level data for asthma ED visit rates organized by counties within New York State. The SPARCS Hospital Inpatient database collects information on all hospital discharges from acute care and rehabilitation hospitals located in New York State. This database includes records for patients who are admitted to the hospital directly from the ED and for those who are hospitalized without first utilizing the ED. The SPARCS Hospital Outpatient database contains information on ED visits who visit the ED but are not hospitalized.
For the SPARCS Hospital Inpatient database, an asthma ED visit was defined as having been admitted to the hospital directly from the ED and having an admitting diagnosis with asthma (International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9-CM) code of 493). For the SPARCS Outpatient database, an asthma ED visit was defined as having a principal diagnosis with asthma (ICD-9-CM code of 493).
Population estimates by ZIP code used for computing the asthma ED visit rates were obtained by the New York State Department of Health (NYSDOH) from the Claritas Corporation.
Data are available for the three-year period 2009-2011. ZIP code rates per 10,000 population were calculated by dividing the total number of asthma ED visits for the three-year period by three to get the average number of asthma ED visits per year. The average number of asthma ED visits was then divided by the average population of the three-year period and multiplied by 10,000. Data for a ZIP code that crosses county boundaries are allocated to one county only (the county that contains the largest geographic portion of that ZIP code).
Rates are available for the following groupings:
- 0-17 years of age
- 18-64 years of age
- 65 years of age and older
- Total population
ZIP codes are marked with a plus (+) when rates are based on less than or equal to ten visits (Relative Standard Error >30%) and are considered unstable (see Frequently Asked Questions About Asthma Emergency Department Visit Data).
Each county table contains the total number of asthma ED visits for a three-year period, the average population for the three-year period, and the three-year average annual ED visit rate per 10,000 population by ZIP code. Data are not shown, due to confidentiality purposes, if the number of ED visits is less than six. ZIP codes are marked with an asterisk when data is suppressed for this reason.
County maps display ZIP code level data geographically by quartile. Regional quartiles were calculated separately for the five boroughs (counties) of New York City and the remaining counties of the state. A ZIP code's color indicates the regional quartile it belongs to. Each map also contains the asthma ED visit rate for the county, New York State, and its region. A non shaded area indicates that part of that ZIP code predominantly lies in an adjacent county.
Why are small numbers of cases or events a concern when looking at health data?
Questions about diseases and conditions such as asthma often lead to looking at the disease in small geographic areas such as neighborhoods and ZIP codes. When the focus is on small areas, the number of health events is likely to be small. When dealing with small numbers of health events, privacy and confidentiality need to be maintained. In addition, people need to be aware that seemingly small changes in the number of events can dramatically change calculated rates.
Data should not be released in a way that may identify a person or release confidential information about that person.
In the tables of asthma ED visits by ZIP code the number of ED visits is not shown if the number of ED visits is less than six. A count of no ED visits is shown in the tables because a count of zero is not a threat to confidentiality.
In an area with a small number of ED visits per year, an increase or decrease of just one or two ED visits per year can cause the ED visit rate to change dramatically from year to year; such a rate is likely to be unstable.
In an area with a large number of ED visits each year, small increases or decreases in the number of ED visits have little effect on the ED visit rate (stable rate). (For additional information on this issue and the relative standard error [RSE], see Rates Based Small Numbers).
In the tables of asthma ED visits by ZIP code, rates based on ten or fewer ED visits (RSE 30%) are considered unstable and are marked with a plus (+). These rates should be interpreted with caution.