Data Use Agreement for HCUP Fast Stats

This Fast Stats topic provides general descriptive statistics on changes in rates of hospital utilization following historical U.S. hurricanes. Information on hospital utilization is based on data from the HCUP State Inpatient Databases (SID) and State Emergency Department Databases (SEDD). Information about the proximity of counties to hurricane paths was derived from the National Oceanic and Atmospheric Association (NOAA) Best Track datasets and the Federal Emergency Management Agency (FEMA) Disaster Declaration Summary database. In order to calculate hospital utilization rates, estimates of the resident population were taken from the U.S. Census Bureau's American Community Survey (ACS).

The hospital utilization statistics reported here may be influenced by a number of factors such as hurricane-related evacuations and hospital closures for which the source data have not been adjusted. These limitations may cause imprecision in the estimates. Please refer to the "Caveats on Data Analysis" section below for more information.

Hurricanes

Eleven hurricanes that impacted the mainland of the United States between 2005 and 2017 are included. States that were affected by these hurricanes were identified based on information on hurricane activity from the National Oceanic and Atmospheric Association (NOAA) and information on counties identified by the Federal Emergency Management Agency (FEMA) as major disaster areas caused by the hurricane. The start date of hurricane activity was identified by the date of the first record that indicated hurricane activity for a State in the NOAA Storm Best Track dataset. Hurricane activity was defined as any one of the following: a tropical cyclone of hurricane intensity with winds greater than 64 knots, a tropical cyclone of tropical storm intensity with winds of 34-64 knots, or an extratropical cyclone with winds of at least 34 knots.

Hospital utilization data from neighboring States not impacted by a hurricane may be included with utilization data from the States impacted by the hurricane. If a patient who resided in a hurricane-impacted State was treated at a hospital in another State, the hospital encounter is included in the utilization count for the patient's county of residence if the hospital was located within 250 miles of the patient's residence. Distance was determined based on the centroids of the ZIP Codes of the hospital and patient's residence.

Hurricane Proximity

Counties in States impacted by the hurricane were classified into one of four proximity categories: direct path, near path, remote/FEMA disaster, and remote/not disaster. These proximity designations were derived from two data sources:

• The Federal Emergency Management Agency (FEMA) Disaster Declaration Summary database identifies whether a county was declared a major disaster area for any one of the 11 hurricanes. For some of these hurricanes, FEMA separately reports major disaster areas under the hurricane's downgraded status of tropical storm. In this analysis, major disaster areas are based on both the hurricane and tropical storm status, where applicable. A county may be declared a major disaster area by FEMA if any one or more of the following types of assistance are needed: individual assistance, individual and household assistance, public assistance, and/or hazard mitigation. FEMA reports data on all emergency declarations and major disaster declarations declared under the Stafford Act.³


• The National Oceanic and Atmospheric Association (NOAA) Best Track datasets provide trajectory and wind speed information for the hurricane.⁴ These hurricane-specific datasets include measurements of the hurricane's location taken at six-hour intervals corresponding to standard synoptic times of 0000, 0600, 1200, and 1800. For some hurricanes, landfall records are recorded with the exact time. Each standard synoptic time observation includes information on the latitude and longitude of the measurement point, in addition to the status of the storm (e.g., tropical cyclone of hurricane intensity, extratropical cyclone, subtropical cyclone), maximum wind speed sustained, minimum central pressure, and distance in nautical miles for three wind radii (34 knots, 50 knots, and 64 knots). Occasionally, non-synoptic time records (for landfall) do not include wind radii information.
  
  Using ESRI Geographic Information Software (ArcGIS),⁵ the latitude and longitude were mapped for each NOAA Best Track measurement point to the corresponding county. The ESRI ArcGIS "USA Counties" layer included detail on coastal landforms. Starting in 2015, NOAA began providing final Best Track "line" files that track the path of a hurricane between measurement points. Because they were publicly available, these files were used to plot the trajectories of the three most recent hurricanes presented in HCUP Fast Stats (Matthew, Harvey, and Irma). For earlier hurricanes, ArcGIS was used to infer the trajectory of the hurricane assuming the shortest possible path between two NOAA Best Track measurement points.

Counties were classified into one of the four hurricane proximity categories as follows:

• Direct path: Counties were classified as being in the direct path of the hurricane based on either of the following criteria:


• The county was identified by the longitude and latitude of a measurement point in the NOAA Best Track dataset and the status and/or wind speed indicated hurricane activity, or
• The county was crossed by the trajectory line between two measurement points with hurricane activity, as determined by the NOAA trajectory information or ArcGIS.

The "direct path" designation was based on the hurricane path only, whether or not the county was declared a major disaster area by FEMA. It is possible, but rare, for counties in the direct path of the hurricane to not be designated as major disaster areas by FEMA.


• Near path: Counties were classified as being near the path of the hurricane based on the wind radii recorded at a measurement point indicating hurricane activity in the NOAA Best Track dataset. The distance in nautical miles from the latitude and longitude of the measurement points to the three wind radii was used to calculate concentric circles containing the strongest winds (64 knots) to the weakest winds (34 knots). Counties within these concentric circles that were not identified as in the direct path of the hurricane were categorized as being near the hurricane path. The "near path" designation was based on the wind radii of the hurricane only, whether or not the county was declared a major disaster area by FEMA. For counties in the near path of the hurricane, some were designated as major disaster areas by FEMA and some were not, depending on the hurricane.


• Remote: Counties were classified as being remote from the hurricane if they were either in States that were affected by the hurricane or in States that had at least one county designated as a FEMA major disaster area and were not classified as in the direct path or near the path of the hurricane. A county remote from the hurricane was then further subdivided into one of two categories, based on whether FEMA declared the county a major disaster area: remote/FEMA disaster designation and remote/not disaster designation. Counties remote from the hurricane were not associated with hurricane activity based on NOAA wind radii data, but they may have been impacted by hurricane-related flooding or secondary storm damage resulting in the FEMA disaster declaration.

Note that one or more proximity categories may not be applicable for some hurricanes if there were no counties classified in a proximity category. For example, all the counties in the affected States could be classified into the direct path, near path, or remote/FEMA disaster proximity categories, and none into the remote/not disaster proximity category.

Hurricane-specific maps displaying the areas designated as direct, near, remote/FEMA disaster, and remote/not disaster are available in an exported data file, which can be downloaded by expanding "Show Data Export Options". The maps document the population at risk for the hurricane and what hospital utilization data were available from the HCUP State databases.

³ https://www.fema.gov/disasters
⁴ https://www.nhc.noaa.gov/gis/
⁵ https://www.esri.com/en-us/arcgis/about-arcgis/overview

Patient County Assignment

Inpatient stays and emergency department (ED) visits were classified into hurricane proximity categories using the patient's county of residence. Patient county was assigned based on the ZIP Code of the patient's residence using the SAS function for ZIP Code to county assignment. For ZIP Codes that cross county boundaries, the SAS function used the geographic centroid of the ZIP Code to assign the county.⁶ A sensitivity test using the 35.4 million records in the 2016 SID demonstrated that the SAS function assigned a county different from the county with the population centroid of the ZIP code in 0.6 percent of SID records. If the patient ZIP Code indicated the patient was homeless (the HCUP data element ZIP = "H"), then the patient county was assigned to be the same as the hospital county. Records for patients with a ZIP Code that was missing, invalid, or indicated the person was from a foreign country were excluded from the tabulated counts. This exclusion dropped less than 1 percent of records in any year.

Additional information on using HCUP data for county-level analyses is available in Method Series Report #2019-04: Conducting County-Level Analyses With HCUP Data: Approaches and Methodological Considerations.

⁶Additional information from SAS on the geocode procedure:
https://support.sas.com/documentation/cdl/en/graphref/65389/HTML/default/viewer.htm#n1cqwrpowwd4l6n1lmw39ughjpuh.htm

Unit of Analysis

The unit of analysis is the hospital discharge (i.e., the hospital inpatient stay) or an emergency department (ED) visit, not a person or patient. This means that a person who is admitted to the hospital or visits the ED multiple times in one year is counted each time as a separate discharge from the hospital or a separate visit in the ED.

For Fast Stats, all stays and visits are counted one time only, regardless of the number of relevant diagnosis or procedure codes that appear on the record. For instance, when identifying injury-related inpatient stays and ED visits, a record may include more than one of the injury-specific codes; in such a case, the record is only included once in the injury counts.

Percent Change from Pre-Hurricane Average for Inpatient Stays or ED Visits

The percent change in the rate of inpatient stays or ED visits compares hospital utilization during and post-hurricane to the pre-hurricane average utilization rates. Time periods are calculated based on the State-specific start date of the hurricane activity (documented under the section on Hurricanes).

• The pre-hurricane rate ("Avg. Pre-Hurr.") was calculated as an average of the rates for the four weeks immediately preceding the start date of the hurricane.
• The rate for the week of the hurricane ("Hurr. Week") includes seven days from the start date of the hurricane (i.e., the starting day of the hurricane and the following six days).
• The post-hurricane rate was examined for each of the seven weeks following the hurricane week ("Post Wk 1" to "Post Wk 7").

The rates by hurricane proximity were population-weighted to account for the different sizes of counties. Population data were obtained from the U.S. Census Bureau, American Community Survey (ACS) overall and by specific age groups. The rate of inpatient stays or rate of ED visits includes the HCUP number of stays or ED visits in the numerator and the U.S. resident population in the denominator (with a multiplier of 10,000). For age, population rates were based on the population for that age group. Population-based rates by hurricane proximity always include data from two or more counties and two or more hospitals. Counties and hospitals may be within the same State or from different States.

The percent change from the pre-hurricane weekly average is presented as the baseline value 0 for the pre-hurricane period. The percent change for the hurricane and each post-hurricane week is calculated from the pre-hurricane weekly average and demonstrates how utilization varied each week from the pre-hurricane period.

Detailed information on the population-based rates and percent change are available in the exported data file (under "Show Data Export Options"). For the pre-hurricane period, the export file includes the 4-week average rate, the average number of weekly encounters (i.e., the average numerator count of HCUP inpatient stays or ED visits), and the Census population count (the population denominator for the rate). For the hurricane week, the export file includes the number of encounters, the population-based rate, and the percent change from the pre-hurricane average rate to the rate for the hurricane week. For each post-hurricane week, the export file includes the number of encounters, the population-based rate, and the percent change from the pre-hurricane average rate to the rate for the post-hurricane week. Counts are rounded to the nearest 10 discharges or ED visits, with any counts less than or equal to 10 or representing fewer than two hospitals suppressed for confidentiality. The exception is raw counts of 11-14, which are rounded to 11.

If the average number of encounters in the pre-hurricane period is less than or equal to 10, or represents fewer than two hospitals, the percent changes for the hurricane week and each post-hurricane week are suppressed. This will result in one or more missing trend lines in a graph. If the number of encounters for the hurricane week or any post-hurricane week is less than or equal to 10, or represents fewer than two hospitals, the percent change is suppressed. This will result in one or more missing data points in a graph and will cause a discontinuity in the trend lines. When three or more data points are suppressed, the trend line is omitted from the graph and none of the data values are provided in the underlying data tables and exported data file. Suppression of multiple trend lines is particularly common in the inpatient setting for age 0-17 years. For some hurricanes, all trend lines may be omitted from certain graphs due to data suppression; in these instances, the graph includes a note indicating that "Data are insufficient for presentation."

Inpatient Stays

Statistics on inpatient stays for each hurricane are from the HCUP State Inpatient Databases (SID) and quarterly data if available. Information based on quarterly data should be considered preliminary. Quarterly data will be replaced by the State's complete annual SID for the year when it is available. As a result, previously reported statistics for a given hurricane may change. For this analysis, the SID are limited to patients treated in community hospitals in the State. Community hospitals are defined as short-term, non-Federal, general, and other hospitals, excluding hospital units of other institutions (e.g., prisons). Included among community hospitals are obstetrics and gynecology, otolaryngology, orthopedic, cancer, pediatric, public, and academic medical hospitals. Excluded are community hospitals that are also rehabilitation and long-term acute care facilities. If a patient was transferred from one community hospital to another, then the SID records for both the transferring and receiving hospitals were included in the analysis.

In any data year for the hurricane-impacted States, an average of 0.6 percent of inpatient stays from community hospitals⁷ are missing from the SID (range of 0.0 to 4.7 percent). These missing discharges represent an average of 3.0 percent of community hospitals⁷ (range of 0.0 to 31.4 percent). One State is missing a total of 4.7 percent of discharges, due to missing 31.4 percent of the community hospitals in the state⁷ (predominately small hospitals with fewer than 50 beds).

⁷Excluded are community hospitals that are also rehabilitation and long-term acute care facilities.

Emergency Department Visits

Emergency department (ED) visits are defined as ED encounters that do not result in a hospital admission to the same hospital (i.e., treat-and-release ED visits).

Statistics on treat-and-release ED visits for each hurricane are from the HCUP State Emergency Department Databases (SEDD) and quarterly data if available. Information based on quarterly data should be considered preliminary. Quarterly data will be replaced by the State's complete annual SEDD for the year when it is available. As a result, previously reported statistics for a given hurricane may change. The SEDD are limited to patients treated in community hospital-owned EDs in the State. Excluded are community hospitals that are also rehabilitation and long-term acute care facilities. If a patient was transferred from the ED, then records for both the transferring and receiving facilities were included in the analysis. There would be a SEDD record from the transferring ED. Most of the time (91 percent), ED transfers result in an inpatient stay. In these cases, the record for the receiving hospital would be included in the SID; otherwise, there would be a second SEDD record.

In any data year for the hurricane-impacted States, an average of 0.4 percent of the ED visits from community hospital-owned EDs⁸ are missing from the SEDD (range of 0.0 to 1.7 percent). These missing ED visits represent an average of 1.0 percent of community hospital-owned EDs⁸ (range of 0.0 to 3.1 percent).

Information on ED utilization is not presented for all hurricanes. Gustav, Ike, Isaac, and Rita lack ED utilization information because none of the impacted states provided ED data corresponding to the hurricane time period. Additionally, some states impacted by hurricanes Harvey, Irene, Matthew, and Sandy provided inpatient data, but no ED data. In this situation, the ED information incorporates data from a smaller set of states than the inpatient information; accordingly the population count is smaller for the ED setting than the inpatient setting.

⁸Excluded are community hospitals that are also rehabilitation and long-term acute care facilities.

Transition in Clinical Coding Used to Define Conditions

In October 2015, the United States transitioned coding systems for reporting diagnoses and inpatient procedures from the International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) to the International Classification of Diseases, Tenth Revision, Clinical Modification/Procedure Coding System (ICD-10-CM/PCS). The following hurricanes would have had diagnoses and procedures reported using ICD-9-CM: Dennis, Rita, Wilma, Gustav, Ike, Irene, Isaac, and Sandy. The following hurricanes would have had diagnoses and procedures reported using ICD-10-CM/PCS: Matthew, Harvey, and Irma. No hurricane has clinical data that crossed coding systems. More information about the use of data across the two coding system may be found on the HCUP User Support (HCUP-US) web page for ICD-10-CM/PCS Resources.

Circulatory

Circulatory is defined using the following Clinical Classifications Software (CCS) for ICD-9-CM categories or Clinical Classifications Software Refined (CCSR) for ICD-10-CM default categorization scheme for the principal (or first-listed) diagnosis as appropriate for the time period of the hurricane. The circulatory condition must be reported as the principal diagnosis on an inpatient stay or the first-listed diagnosis on an emergency department visit. The principal or first-listed diagnosis is used so that a record is only assigned to one specific clinical condition.

Percent change in population rates for circulatory conditions is not reported for age 0-17 years because these conditions are relatively uncommon for this age group.

• CIR001: Chronic rheumatic heart disease
• CIR002: Acute rheumatic heart disease
• CIR003: Nonrheumatic and unspecified valve disorders
• CIR004: Endocarditis and endocardial disease
• CIR005: Myocarditis and cardiomyopathy
• CIR006: Pericarditis and pericardial disease
• CIR009: Acute myocardial infarction
• CIR010: Complications of acute myocardial infarction
• CIR011: Coronary atherosclerosis and other heart disease
• CIR012: Nonspecific chest pain
• CIR013: Acute pulmonary embolism
• CIR014: Pulmonary heart disease
• CIR016: Conduction disorders
• CIR017: Cardiac dysrhythmias
• CIR018: Cardiac arrest and ventricular fibrillation
• CIR019: Heart failure
• CIR020: Cerebral infarction
• CIR021: Acute hemorrhagic cerebrovascular disease
• CIR022: Sequela of hemorrhagic cerebrovascular disease
• CIR023: Occlusion or stenosis of precerebral or cerebral arteries without infarction
• CIR025: Sequela of cerebral infarction and other cerebrovascular disease
• CIR026: Peripheral and visceral vascular disease
• CIR027: Arterial dissections
• CIR029: Aortic; peripheral; and visceral artery aneurysms
• CIR030: Aortic and peripheral arterial embolism or thrombosis
• CIR033: Acute phlebitis; thrombophlebitis and thromboembolism
• CIR034: Chronic phlebitis; thrombophlebitis and thromboembolism
• NVS012: Transient cerebral ischemia

• 96: Heart valve disorders
• 97: Peri-; endo-; and myocarditis; cardiomyopathy (except that caused by tuberculosis or sexually transmitted disease)
• 100: Acute myocardial infarction
• 101: Coronary atherosclerosis and other heart disease
• 102: Nonspecific chest pain
• 103: Pulmonary heart disease
• 105: Conduction disorders
• 106: Cardiac dysrhythmias
• 107: Cardiac arrest and ventricular fibrillation
• 108: Congestive heart failure; nonhypertensive
• 109: Acute cerebrovascular disease
• 110: Occlusion or stenosis of precerebral arteries
• 112: Transient cerebral ischemia
• 114: Peripheral and visceral atherosclerosis
• 115: Aortic; peripheral; and visceral artery aneurysms
• 116: Aortic and peripheral arterial embolism or thrombosis
• 118: Phlebitis; thrombophlebitis and thromboembolism

Infections

Infection is defined using the following Clinical Classifications Software (CCS) for ICD-9-CM categories or Clinical Classifications Software Refined (CCSR) for ICD-10-CM default categorization scheme for the principal (or first-listed) diagnosis as appropriate for the time period of the hurricane. An infection must be reported as the principal diagnosis on an inpatient stay or the first-listed diagnosis on an emergency department visit. The principal or first-listed diagnosis is used so that a record is only assigned to one specific clinical condition.

• INF001: Tuberculosis
• INF002: Septicemia
• INF003: Bacterial infections
• INF004: Fungal infections
• INF006: HIV infection
• INF007: Hepatitis
• INF008: Viral infection
• INF009: Parasitic, other and unspecified infections
• INF010: Sexually transmitted infections (excluding HIV and hepatitis)

• 1: Tuberculosis
• 2: Septicemia (except in labor)
• 3: Bacterial infection; unspecified site
• 4: Mycoses
• 5: HIV infection
• 6: Hepatitis
• 7: Viral infection
• 8: Other infections, including parasitic
• 9: Sexually transmitted infections (not HIV or hepatitis)

Injuries

Injury is defined using the following ICD-9-CM or ICD-10-CM diagnosis codes as appropriate for the time period of the hurricane. The injury must be reported as the principal diagnosis on an inpatient stay or the first-listed diagnosis on an emergency department visit. The principal or first-listed diagnosis is used so that a record is only assigned to one specific clinical condition.

• S00-S99 series: Injuries to the head; neck; thorax; abdomen, lower back, lumbar spine, pelvis and external genitals; shoulder and upper arm; elbow and forearm; wrist, hand and fingers; hip and thigh; knee and lower leg; ankle and foot
• Includes only initial encounters with a 7th character of A, B, C, or missing
• T07-T34 series: Injuries involving multiple body regions; injury of unspecified body region; effects of foreign body entering through natural orifice; burns and corrosions of external body surface, specified by site; burns and corrosions confined to eye and internal organs; burns and corrosions of multiple and unspecified body regions; frostbite
  • Includes only initial encounters with a 7th character of A, B, C, or missing
• T36-T50 series: Poisoning by, adverse effect of and underdosing of drugs, medicaments, and biological substances
• Includes only codes with a 6th character of 1, 2, 3, or 4 indicating poisoning
• Excludes adverse effects and underdosing of drugs, medicaments and biological substances (codes with the 6th character of 5 or 6) with the following exceptions: T36.9, T37.9, T39.9, T41.4, T42.7, T43.9, T45.9, T47.9, and T49.9 with a 5th character of 1, 2, 3, or 4
• Includes only initial encounters with a 7th character of A, B, C, or missing
• T51-T76 series: Toxic effects of substances chiefly nonmedicinal as to source; other and unspecified effects of external causes: radiation sickness, unspecified; effects of heat and light; hypothermia; other effects of reduced temperature; effects of air pressure and water pressure; asphyxiation; effects of other deprivation; adult and child abuse, neglect and other maltreatment, confirmed; other and unspecified effects of other external causes; adult and child abuse, neglect and other maltreatment, suspected
• Includes only initial encounters with a 7th character of A, B, C, or missing
• T79 series: Certain early complications of trauma, not elsewhere classified
  • Includes only initial encounters with a 7th character of A, B, C, or missing
• M97 series (valid as of October 1, 2016) or T8404 series (valid prior to October 1, 2016): Periprosthetic fracture around internal prosthetic joint
  • Includes only initial encounters with a 7th character of A, B, C, or missing
• O9A2-O9A5 series: Injury, poisoning, physical abuse, sexual abuse, psychological abuse, and other consequences of external causes complicating pregnancy, childbirth and the puerperium
• Includes only initial encounters with a 7th character of A, B, C, or missing

• 800-909.2: 909.4: 909.9: Fracture of skull, spine, trunk, upper limb, and lower limb; dislocation; sprains and strains of joints and adjacent muscles; intracranial injury, excluding those with skull fracture; internal injury of chest, abdomen, and pelvis; open wound of the head, neck, trunk, upper limb, and lower limb; injury to blood vessels; late effects of injury, poisonings, toxic effects, and other external causes, excluding those of complications of surgical and medical care and adverse effect of drugs, medicinal or biological substance
• 910-994.9: Superficial injury; contusion with intact skin surface; crushing injury; effects of foreign body entering through orifice; burns; injury to nerves and spinal cord; certain traumatic complications and unspecified injuries; poisoning by drugs, medicinals and biological substances; toxic effects of substances chiefly nonmedicinal as to source; other and unspecified effects of external causes
• 995.50-995.59: Child maltreatment syndrome
• 995.80-995.85: Adult maltreatment, unspecified; adult physical abuse; adult emotional/ psychological abuse; adult sexual abuse; adult neglect (nutritional); other adult abuse and neglect

Respiratory

Respiratory is defined using the following Clinical Classifications Software (CCS) for ICD-9-CM categories or Clinical Classifications Software Refined (CCSR) for ICD-10-CM default categorization scheme for the principal (or first-listed) diagnosis as appropriate for the time period of the hurricane. The respiratory condition must be reported as the principal diagnosis on an inpatient stay or the first-listed diagnosis on an emergency department visit. The principal or first-listed diagnosis is used so that a record is only assigned to one specific clinical condition.

• RSP001: Sinusitis
• RSP002: Pneumonia (except that caused by tuberculosis)
• RSP003: Influenza
• RSP005: Acute bronchitis
• RSP006: Other specified upper respiratory infections
• RSP007: Other specified and unspecified upper respiratory disease
• RSP008: Chronic obstructive pulmonary disease and bronchiectasis
• RSP009: Asthma
• RSP011: Pleurisy, pleural effusion and pulmonary collapse
• RSP012: Respiratory failure; insufficiency; arrest
• RSP014: Pneumothorax
• RSP016: Other specified and unspecified lower respiratory disease

• 122: Pneumonia (except that caused by tuberculosis or sexually transmitted disease)
• 123: Influenza
• 125: Acute bronchitis
• 126: Other upper respiratory infections
• 127: Chronic obstructive pulmonary disease and bronchiectasis
• 128: Asthma
• 130: Pleurisy; pneumothorax; pulmonary collapse
• 131: Respiratory failure; insufficiency; arrest (adult)
• 133: Other lower respiratory disease
• 134: Other upper respiratory disease

Age

Age refers to the age (in years) of the patient at admission. Discharges or visits missing age are excluded from results reported by age. Age is grouped into three categories: 0-17 years, 18-64 years, and 65+ years. Less than 0.05 percent of records are missing information on age.

Caveats on Data Analysis

It is important to note that there were certain limitations to the data used for this analysis.

The six-hour intervals between measurement points in the NOAA Best Track datasets could result in gaps in information if the storm was fast moving. The use of geographic circles defined by wind radii to classify counties as impacted by the hurricane may be overgenerous in identification (e.g., when only the outside edge of the wind radii circle touches the border of the county or one small coastal island) and may not identify counties that would have been detected if a shape other than a circle was used. For some hurricanes, there is incomplete wind radii information as a storm nears dissipation, making the end of the hurricane difficult to determine. For this analysis, NOAA Best Track data records with incomplete wind radii information are not included.

The county-specific population data were annual counts from the U.S. Census Bureau, American Community Survey (ACS). The information would not have taken into account evacuations prior to the hurricane making landfall, seasonal migration patterns (e.g., elderly living in Florida during the winter), people who resided in a county impacted by the hurricane but who were not in the area at the time of the hurricane, or people from counties not impacted by the hurricane visiting the area at the time of the hurricane.

Information on hospital closures around the time of the hurricane was unavailable. In addition, hospitals may have had difficulty reporting utilization to the HCUP Partner organization (or were temporarily considered exempt from reporting) resulting in an underestimate of utilization using the SID and SEDD. Hospital care just prior to the hurricane may have been the result of preparing for the hurricane. In contrast, hospital care after the hurricane may not be hurricane related.

Suppression of data points, trend lines, or entire graphs was frequently applied to condition-specific selections for age 0 to 17 years, especially in the inpatient setting. For a detailed description of the suppression rules used in this topic, refer to the section "Percent Change from Pre-Hurricane Average for Inpatient Stays or ED Visits" above.