Asthma is a chronic disease characterized by bronchoconstriction (tightening of muscles surrounding the airways), airway inflammation (swelling), and increased mucus production in the airways, making breathing more difficult. During normal breathing, air flows freely into and out of the lungs, with mucus typically shielding the airways from environmental irritants such as dust, bacteria, and smoke. However, during an asthma episode, the airways become overly responsive to environmental triggers, airways may tighten and constrict, and mucus production my increase substantially, resulting in wheezing, coughing, breathlessness, or tightness in the chest.
While there is currently no cure for asthma, it can be treated by taking medicines every day that prevent (control) symptoms from developing, using inhalable (quick relief) medicines when necessary, avoiding things that cause (trigger) asthma symptoms to flare up, and living a healthy lifestyle. It’s important to work with your health care provider to create an asthma self-management plan (also called an asthma action plan or AAP) that works for you.
The Minnesota Pollution Control Agency tracks ambient air pollutants, including particulate matter and ozone, in Minnesota. MPCA and MDH are working to evaluate the public health impacts of air pollution on health, and to communicate information about the Air Quality Index (AQI).
The MDH Indoor Air Quality Program enforces the Minnesota Clean Indoor Air Act, which regulates smoking in indoor public places, tracks research about the health effects of air pollutants on an ongoing basis, and incorporates new methods and data into health risk assessments and best practices guidelines.
Asthma in Minnesota: A Strategic Framework 2026-2030 outlines efforts to improve asthma care and management across Minnesota. It is intended to reach and reflect the priorities of all communities from Greater Minnesota to the Twin Cities metro area, children and youth to elderly, and individuals of all abilities, family structures, and other differences that contribute to the richness of our state.
Minnesota Asthma Alliance (MAA) includes individuals from health care, local public health, Tribal health, schools, local business, and nonprofit organizations that have professional and/or personal experience with asthma and commitment to tackling asthma across Minnesota. The MAA meets quarterly as a full group to exchange ideas and to collectively problem-solve and strategize with Asthma Program staff on activities and initiatives.
Asthma hospitalization data are extracted from Minnesota Hospital Discharge Data (MNHDD), which is maintained by the Minnesota Hospital Association (MHA). MHA represents Minnesota's hospitals and health systems. Hospitals submit inpatient discharge data to MHA using a standardized billing form. In 2021, 90% of all hospitals in the state reported hospital discharge data to the MHA. MHA began data-sharing agreements with several states in 2005. Emergency Department visits are defined as Minnesota residents receiving care at an emergency facility in Minnesota or North Dakota who are treated and released or subsequently admitted to the hospital.
Emergency department visit rates by year
Emergency department visits by age and month
Emergency department visit rates by age and region
Emergency department visit rates by age and sex
Asthma emergency department visit rates in Minnesota
Asthma-associated emergency department visit rates have been in decline since 2016; a drop was observed in 2020, potentially associated with the COVID-19 pandemic.
Source: Minnesota Hospital Association. ICD: The International Classification of Disease (ICD) coding changed for asthma on October 1st, 2015. Rates from 2014 and earlier should not be compared to rates after the coding change.
Daily asthma emergency department visits in Minnesota, by age and month in 2022
Asthma-associated emergency department (ED) visits in Minnesota follow a seasonal pattern with the highest numbers of ED visits occurring in autumn and the lowest in summer.
Source: Minnesota Hospital Association.
Asthma emergency department visit rates in Minnesota, by age and region in 2022
Children under the age of 18 living in the 7-county Twin Cities metropolitan area have higher rates of asthma-associated emergency department (ED) visits compared to those living in Greater Minnesota. ED visit rates for adults are similar between the two regions.
Source: Minnesota Hospital Association.
Asthma emergency department visit rates by age and sex in 2022
Rates of asthma-associated emergency department visits generally decrease with increasing age. Among teens and adults, rates tend to be slightly higher for females than males, while among children under the age of 15, rates are higher among males.
Source: Minnesota Hospital Association.
Emergency department visit rates (County)
Emergency department visit rates (ZIP code)
Age 0-17 emergency department visit rates (ZIP code)
Age 18+ emergency department visit rates (ZIP code)
Asthma emergency department visit rates for 2020-2022 by county
Age-adjusted rates of asthma emergency department (ED) visits by county.
Source: Minnesota Hospital Association. Rates based on counts less than or equal to 20 should be interpreted with caution; the rate maybe unstable because it can change dramatically with the addition or subtraction of one case. To protect an individual's privacy, hospitalization counts under 5 are suppressed if the underlying population is less than or equal to 100,000.
Asthma emergency department visit rates for 2018-2022 by ZIP Code
Age-adjusted rates of asthma emergency department (ED) visits by ZIP code.
Source: Minnesota Hospital Association. Rates based on counts less than or equal to 20 should be interpreted with caution; the rate maybe unstable because it can change dramatically with the addition or subtraction of one case. To protect an individual's privacy, hospitalization counts under 5 are suppressed if the underlying population is less than or equal to 100,000.
Asthma emergency department visit rates for age 0-17 by ZIP Code, 2018-2022
Age-adjusted rates of asthma emergency department (ED) visits for 2018 - 2022 by ZIP code.
Source: Minnesota Hospital Association. Rates based on counts less than or equal to 20 should be interpreted with caution; the rate maybe unstable because it can change dramatically with the addition or subtraction of one case. To protect an individual's privacy, hospitalization counts under 5 are suppressed if the underlying population is less than or equal to 100,000.
Asthma emergency department vist rates for age 18+ by ZIP Code, 2018-2022
Age-adjusted rates of asthma emergency department (ED) visits for 2018-2022 by ZIP code.
Source: Minnesota Hospital Association. Rates based on counts less than or equal to 20 should be interpreted with caution; the rate maybe unstable because it can change dramatically with the addition or subtraction of one case. To protect an individual's privacy, hospitalization counts under 5 are suppressed if the underlying population is less than or equal to 100,000.
Asthma hospitalization data are extracted from Minnesota Hospital Discharge Data (MNHDD), which is maintained by the Minnesota Hospital Association (MHA). MHA represents Minnesota's hospitals and health systems. Hospitals submit inpatient discharge data to MHA using a standardized billing form. In 2021, 90% of all hospitals in the state reported hospital discharge data to the MHA.
MHA began data-sharing agreements with several states in 2005. Hospitalizations are defined as Minnesota residents who are discharged from a hospital in Minnesota or Emergency Department visits are defined as Minnesota residents receiving care at an emergency facility in Minnesota or North Dakota who are treated and released or subsequently admitted to the hospital.
Data Questions
The numbers and rates of asthma hospitalizations and emergency department (ED) visits in Minnesota by year, age group and gender.
If an asthma 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 asthma.
To inform the public about asthma hospitalizations and ED visits.
For program planning and evaluation by state and local partners.
What causes asthma, or what leads to asthma hospitalizations and ED visits.
The total burden of asthma in a population.
The number of people who are hospitalized or who visited the ED due to asthma. Because personal identifiers are removed from the hospital discharge data before analysis, individuals who have multiple hospitalizations or ED visits cannot be identified.
Hospitalizations visits are defined as Minnesota residents who are discharged from a hospital in Minnesota or the bordering states of North Dakota, South Dakota, or Iowa. Emergency Department visits are defined as Minnesota residents who are treated and released or subsequently admitted to a facility in Minnesota or North Dakota.
Asthma hospitalizations have a primary discharge diagnosis of asthma. Asthma ED visits have asthma as the first-listed diagnosis. Asthma is defined as the International Classification of Disease 9th Revision, Clinical Modification (ICD-9-CM) codes 493.0-493.9. ICD-10 codes were used starting October 2015, these include the first diagnosis of J45. ED visits include both patients treated and released from the ED as well as those that enter the ED and are admitted to the hospital.
Records with missing county are included in the state count but excluded from county counts.
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 for asthma.
To protect an individual's privacy, hospitalizations 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 confidence interval. A rate is a ratio between two measures with different units. In our analysis a rate is calculated using a numerator, the number of asthma 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 make the number more legible.
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 crude rate but is calculated within an age group (e.g. an age-specific rate of asthma hospitalizations in adults 35-44 years of age).
Assessing the confidence interval for the percent or rate is one approach to determine whether there are differences over time or compared to another location. If they do not overlap then they differ. Although it is not a true statistical test, it is a commonly accepted way to compare percents or rates and tends to be more conservative than statistical testing.
A confidence interval for a rate is a measure of reliability. In this analysis, 95% confidence intervals were calculated. A 95% confidence interval is the interval within which the true value of the rate would be expected to fall 95 times out of 100. When the number of events is fewer than 100, the 95% confidence interval is calculated based on the inverse gamma distribution in this analysis. When the number of events is 100 or greater, the 95% confidence interval is calculated based on normal approximation.
Multiple hospitalizations or ED visits by the same patient cannot be identified, and are not excluded. These data are not appropriate for estimating the total burden of asthma.
Minnesota residents discharged from Wisconsin hospitals are not included, so hospitalization and ED visit rates for counties in which residents are likely to receive care from Wisconsin may be underestimated. Rates for counties in which residents are likely to visit hospitals that do not submit data to the Minnesota Hospital Association (e.g., Veteran's Administration or Indian Health Services hospitals) may also be artificially low. There is usually a two year lag period before hospitalization and ED visit data are available.
The counts are not whole numbers due to how we determined county. To calculate the number of counts per county, we used zip codes to figure out which county each case belongs to. Some zip codes in Minnesota cross county boundaries, so a weighted method is used to split cases. For example, in the zip code 56318 60% of people live in Todd County and 40% live in Morrison County. So a hospitalization or ED visit with this zip code would add 0.6 count to Todd County and 0.4 to Morrison County. This ensures each county is represented as accurately as possible given we only have zip code information.
Data are aggregated over multiple years to allow visualization of more county or ZIP Code data than viewing data in one-year segments would allow.
To learn more about asthma, contact the MDH Asthma Program. For more about the asthma hospitalization data and measures developed by the MN Tracking Program, contact us at at health.dataportal@state.mn.us.
