Definition of Reported Measures
- Hospitalizations due to Heat-related Illness represents the number of hospitalizations due to heat-related illness among California residents; expressed as a rate per 100,000 California residents.
- Emergency department (ED) visits due to Heat-related Illness represents the number of ED visits due to heat-related illness among California residents; expressed as a rate per 100,000 California residents.
How to Read Tables, Charts, and Maps
- The 95% confidence interval (CI) is the range of values that likely contains the true rate in the population.
- Crude rates express the number of outcomes relative to the size of the population. N/A indicates that the data are not available due to the number of events being less than 12.
- Total counts are listed next to rates unless the total number of events is less than 12. The map legend displays the data with four class breaks, where the data is divided into four equal bins known as quartiles.
- Some counties have a greater proportion of people who are old or young than other counties, which makes it di cult to compare across counties or over time. Scientists often x this problem through a technique called age adjustment so comparisons can be made. In addition to crude rates, we also present age-adjusted rates.
- Effective October 1, 2015, hospital record (HCAI) data transitioned from ICD-9 to ICD-10-CM. Di erences between counts and rates in years prior to 2015 compared with 2015 and subsequent years could be a result of this coding change and not an actual di erence in the number of events. Prior to 2019, data for Asians and Paci c Islanders were combined into a single group (Asian/PI). Beginning in 2019, data were reported separately for Asians and Native Hawaiian Paci c Islanders (NHPI). Data were also reported for Multi-race individuals starting in 2019.
Data Sources
- Emergency Department and Patient Discharge Datasets are from the California Department of Health Care Access and Information (HCAI), formerly known as the Office of Statewide Health Planning and Development (OSHPD).
- Denominators for rates are based on estimates from the California Department of Finance.
Methods
- Cases were limited to those occurring between May 1 and September 30 of each year.
Cases of heat-related hospitalizations and emergency department visits are identi ed by using the following ICD-9-CM and ICD-10-CM codes (as of 10/01/2015) listed anywhere in the record (i.e. primary or other diagnosis elds) :
| ICD-9 Code | Code Description |
| 992.0 | Heat stroke and sunstroke |
| 992.1 | Heat syncope |
| 992.2 | Heat cramps |
| 992.3 | Heat exhaustion from water depletion |
| 992.4 | Heat exhaustion from salt depletion |
| 992.5 | Heat exhaustion, unspecified |
| 992.6 | Heat fatigue, transient |
| 992.7 | Heat edema |
| 992.8 | Other specified heat effects |
| 992.9 | Unspecified effects of heat and light |
| E900.0 | Heat effect caused by excessive heat due to weather (e.g. sunstroke, ictur solaris/heatstroke) |
| E900.9 | Effect from unknown cause of excessive heat |
Cases that were due to a man-made source of heat (E900.1) are excluded from this case definition.
| ICD-10 Code | Code description |
| T67.0 | Heat stroke and sunstroke |
| T67.1 | Heat syncope |
| T67.2 | Heat cramps |
| T67.3 | Heat exhaustion from water depletion |
| T67.4 | Heat exhaustion from salt depletion |
| T67.5 | Heat exhaustion, unspecified |
| T67.6 | Heat fatigue, transient |
| T67.7 | Heat edema |
| T67.8 | Other specified heat effects |
| T67.9 | Unspecified effects of heat and light |
| X30 | Exposure to excessive natural heat |
| X32 | Exposure to sunlight*--only used for ED/Hospitalization |
Cases that were due to a man-made source of heat (W92) are excluded from this case definition.
The number of heat-related illness events may differ from other sites due to differences in methods and ICD codes included.
Limitations of the data
- Data Collection Purpose - Diagnosis codes are recorded by hospitals for reimbursement purposes and not for public health surveillance.
- The rates provided include ED visits and hospitalizations for California residents. Out-of-state residents and unhoused patients with no recorded address are excluded from the rates.
- Low-level of resolution- Hospitals are not mandated to report patient addresses. The level of geographic resolution of the data is limited to state, county, and zip code.
- Heat stress can manifest in a number of clinical outcomes, and people with chronic health problems (e.g., cardiovascular disease, diabetes, obesity) are more susceptible to the e ects of heat than healthy individuals. This measure does not capture the full spectrum of heat stress, where exposure to excess heat is not explicitly documented.
Additional Data Tables
Statewide Heat-related Deaths (2000–2019)
Total Heat-related illness by County (2000–2020)
Suggested Citation
Tracking California, Public Health Institute. Heat Related Illness Emergency Department & Hospitalization data. Accessed [Month/Day/Year] from https://data.trackingcalifornia.org
Notes about the data (PDF)