About Heat Related Illness Data
Tracking heat related illness involves collecting data about the number of hospital or emergency room visits due to heat related illness.
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 heat-related illness hospitalizations and emergency department (ED) visits in Iowa by year, age group and gender.
- If a heat-related illness 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 ED due to heat-related illness.
Back to top
How we can use these data?
- To inform the public about heat-related illness hospitalizations and ED visits.
- For program planning and evaluation by state and local partners.
Why is it difficult to measure heat health outcomes?
- Heat-related illness can manifest in numerous and unobvious ways, for this reason heat may not be listed as the primary diagnosis. This analysis only captures cases where heat-related illness is explicitly listed and thus does not capture the full extent of heat-related illness, since they are sometimes not coded as heat-related.
- Deaths attributed to heat are very rare because often heat-related illness may not be listed as the underlying cause of death. This analysis only includes deaths where heat-related illness is explicitly recorded as an underlying or contributing cause of death and does not capture the full extent of heat-related deaths.
Back to top
What can these data not tell us?
- What causes heat-related illness, or what leads to heat-related illness hospitalizations and ED visits.
- The total burden of heat-related illness in a population.
- The number of people who are hospitalized or who visited the ED due to heat-related illness. Because personal identifiers are removed from the hospital before analysis, individuals who have multiple hospitalizations or ED visits cannot be identified.
Back to top
What is the source of the data?
- Hospitalization and emergency department data are collected by the Iowa Hospital Association on behalf of in accordance with Iowa Code section 135.166.
- 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.
Back to top
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.
Back to top
How are heat-related illness hospitalizations and Emergency Department (ED) 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.
- Heat-related illness hospitalizations/ED visits are defined as having a diagnosis of Heat-related illness from a non-man made source.
- Heat-related illness hospitalizations/ED visits are only counted when they occur in May - September.
- Heat-related illness is defined as the International Classification of Disease 9th Revision, Clinical Modification () codes that begin with 992, and an of E900.0 or E900.9; excluding records that have an injury code of E900.1.
- Heat-related illness is defined as the International Classification of Disease 10th Revision, Clinical Modification () codes that begin with T67, X30, or X32; excluding records that have any code that begins with W92.
Back to top
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 ED visits due to heat-related illness, but not the number of unique individuals hospitalized or who visited the ED.
- To protect an individual's privacy, counts from 1 to 5 are suppressed if the underlying population is less than or equal to 100,000.
Rate:
- If you want to understand the probability or what is the underlying risk in a population, then use a rate and . A rate is a ratio between two measures with different units. In our analysis a rate is calculated using a numerator, the number of heat-related illness hospitalizations during a period of time, divided by a denominator, the number of people at risk in a population during the same period of time. This fraction is then multiplied by a constant (in this case 10,000) to provide a more recognizable value.
- To protect an individual's privacy, counts from 1 to 5 and rates based on counts from 1 to 5 are suppressed if the underlying population is less than or equal to 100,000.
- Rates based on counts of 20 or less are flagged as unstable and should be interpreted with caution. These rates are unstable because they can change dramatically with the addition or subtraction of one case.
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.
Age-specific rate:
- A rate of an event (such as disease or death) measured within a particular age group. It is similar to a but is calculated within an age group (e.g. an age-specific rate of heat-related illness hospitalizations in adults 35-44 years of age).
Back to top
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 heat-related illness.
- These measures use hospital admission dates while other public health programs use the hospital discharge dates to count heat-related illness cases. This may cause a difference in heat-related illness 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.
Back to top
Where can I find more technical information about the data?
More detailed documentation of the heat-related illness hospitalization and emergency department visit data can be found in the following documents:
Indicator Profiles
Emergency Department Visits for Heat Related Illness 
Hospitalizations for Heat Related Illness
Descriptive Metadata
Emergency Department Visits for Heat Related Illness
Hospitalizations for Heat Related Illness
Contact Us to learn more about heat-related illness, hospitalization and emergency department visit data, or any of the measures displayed on the Iowa Public Health Tracking Portal.
Back to top