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Frequently Asked Questions - Asthma

Hospitalization (All Ages)

What is asthma hospitalization tracking?

Asthma hospitalization tracking, or surveillance, is the ongoing collection, analysis, and interpretation of asthma hospitalization data, including inpatient admissions and emergency department visits. The MA EPHT Program uses data on hospital admissions and ED visits related to asthma to reflect the public health burden of the disease.

Why is the MA EPHT Program tracking asthma hospitalization?

In 2002, Massachusetts was one of seven states across the U.S. to be awarded funds from the U.S. Centers for Disease Control and Prevention (CDC) to track health conditions thought to be impacted by the environment. A large number of epidemiologic studies have reported associations between air pollution exposure and asthma. Asthma is the leading chronic health condition among children. There are also large racial, income, and geographic disparities in asthma. Tracking asthma can aid in identifying populations or areas with inadequate routine medical care and assist in monitoring the burden of asthma, asthma trends, and how asthma affects health-related quality of life.  

What information can be obtained from tracking asthma hospitalization?

Tracking asthma hospitalization using a standardized method will allow for the monitoring of trends over time; help identify high risk groups that may be more susceptible to asthma incidents; and assist with prevention, evaluation, and program planning efforts. In the future, asthma hospitalization data will be linked to air pollution data to provide more in-depth examination of linkages between environmental and health data to assess potential public health impacts at the community level, and guide disease prevention and intervention programs.

What is the difference between asthma hospital inpatient admissions and asthma emergency department (ED) visits and why does the MA EPHT Program track both?

Most, but not all, asthma hospitalizations begin with an ED visit. After being examined and/or treated in the ED, some patients are then discharged while others require further monitoring or treatment and are admitted to the hospital as inpatients. Less frequently, a patient may have a scheduled asthma-related procedure or doctor's visit that requires an inpatient hospital admission, but does not involve the ED.

The MA EPHT Program tracks both types of hospital visits because they each provide useful, but different information about asthma-related hospitalizations in the state. Looking at asthma ED visits gives the best estimate of the total number of asthma-related hospital visits, excluding only the small number of asthma hospitalizations that begin as inpatient admissions. On the other hand, asthma inpatient admissions represent the number of asthma hospitalizations serious enough to require a hospital stay longer than 24 hours.

Since there is overlap between the two measures in that many patients are included in both the inpatient and ED hospitalization datasets, asthma counts and rates should not be summed across the two measures of hospitalization.

What is the relationship between asthma and air pollution?

Acute asthma attacks can be triggered by indoor and outdoor air pollutants and allergens. Twenty percent of the U.S. population, nearly 55 million people, spends their days in elementary and secondary schools. In the mid-1990s, studies showed that 1 in 5 of our nation's 110,000 schools reported unsatisfactory indoor air quality, and 1 in 4 schools reported ventilation problems - which impacts indoor air quality - as unsatisfactory. Indoor air allergens include mold and radon. The outdoor air pollutants most commonly linked to asthma attacks are particulate matter and ozone. The US EPA Air Quality Index (AQI) is an index for reporting daily air quality. The AQI tells you how clean or polluted your air is, and what associated health effects might be a concern for you.  

How do I interpret a rate and what is the difference between age-specific, crude, and age-adjusted rates?

A rate tells us how frequently a disease or disease-related event (in this case asthma hospitalization) is occurring in a population. An age-specific rate for asthma is calculated for each age group to show how the rate of asthma hospitalization changes with age. A crude rate for asthma is the number of asthma admissions over a specified period of time, divided by the total population. An age-adjusted rate enables comparisons to be made between populations which have different age structures (e.g. between two counties or between one community and the state as a whole).

What is a confidence interval?

To determine if a community's asthma hospitalization rate is significantly different from the state rate or if the difference may be due solely to chance, a 95% confidence interval (CI) is calculated for each rate. A 95% CI assesses the magnitude and stability of a measure. Specifically, a 95% CI is the range of estimated values that has a 95% probability of including the true rate for the population. 

A method for determining if one hospitalization rate estimate is statistically significantly different from another is by comparing the CIs. If the 95% CI for the rate of one community or population does not overlap the CI of another, then it can be concluded that the two populations are statistically significantly different from each other. If the 95% CIs do overlap, then the hospitalization rates of the two populations are likely not statistically significantly different from one another.

"Statistically significantly different" means that the difference observed between the two rates will occur by chance less than 5 percent of the time. For example, if the rate of asthma hospitalization in community A is 5.6 with a 95% CI of 4.8-6.4 and the state rate of asthma hospitalization is 10.2 with a CI of 10.0-10.4, then the two 95% CIs do not overlap. In other words, no part of the 95% CI for community A falls within the range of the state's 95% CI. Therefore, it is concluded that community A's asthma hospitalization rate of 5.6 is statistically significantly different than the state estimate of 10.2. It can also be said, since community A's rate is lower than the state's, that community A's rate is statistically significantly lower than the state rate.   

What are limitations of the data?

  • Data may only be presented to the public if confidentiality guidelines of the MDPH and CHIA are followed through data aggregation and/or suppression in order to protect privacy. Access to restricted data must follow the application procedure specified on the MDPH website.
  • Hospitalization data, by definition, do not include individuals who do not receive medical care or who are not hospitalized, including those who die in emergency rooms, in nursing homes, or at home without being admitted to a hospital, and those treated in outpatient settings. 
  • Data may exclude admissions from specialty hospitals (e.g. psychiatric), long-term care facilities, and federal hospitals which are exempt from state reporting requirements.
  • Transfers from one hospital to another may be included in the dataset as separate hospitalization events.
  • Reporting rates at the state and/or county level will not show the true disease burden at a more local level (i.e., neighborhood).
  • Reporting rates at the state and/or county level will not be geographically resolved enough to be linked with many types of environmental data.
  • When comparing rates across geographic areas, a variety of non-environmental factors, such as access to medical care, can impact the likelihood of persons hospitalized for asthma.
  • When looking at small geographic levels (e.g., zip code), users must take into consideration appropriate cell suppression rules imposed by the data providers or individual state programs.
  • Differences in rates by time or area may reflect differences or changes in diagnostic techniques and criteria and in the coding of asthma.
  • Rates are based on the residential location of cases and not necessarily the location where incidents occur.
  • Numbers and rates may differ slightly from those contained in other publications. These differences may be due to file updates, differences in calculating rates and updates in population estimates.

Where can I get additional information on asthma?

More information is available from the websites listed here: Related Links for Asthma Hospitalization

Pediatric Asthma

What is Pediatric Asthma Tracking?

Pediatric asthma tracking, or surveillance, is the ongoing collection, analysis, and interpretation of asthma data in a population of students in grades K-8. The Massachusetts Department of Public Health/Bureau of Environmental Health (MDPH/BEH) elected to track asthma in children who are enrolled in approximately 2200 public and private schools, grades K through 8, in order to learn how much asthma exists in the state and which communities may have more asthma than others.  This enables the MDPH/BEH to plan targeted public health interventions.

Why is the Massachusetts Department of Public Health tracking pediatric asthma?

In 2002, Massachusetts was one of seven states across the U.S. to be awarded funds from the U.S. Centers for Disease Control and Prevention (CDC) to track health conditions thought to be impacted by the environment.  A number of epidemiologic studies have reported associations between air pollution exposure and asthma.

By participating in the CDC’s National Environmental Public Health Tracking (EPHT) Program, MDPH/BEH is making the epidemic of pediatric asthma a priority focus of public health. Asthma is the leading chronic health condition among children and there are large racial, socioeconomic, and geographic disparities in asthma. Tracking pediatric asthma can aid in identifying populations or areas with inadequate routine medical care and monitoring the burden of asthma, asthma trends, and the effects of asthma on health-related quality of life.

Which schools participate in the MDPH/BEH pediatric asthma tracking program?

All schools in Massachusetts (public, private, charter, and collaborative) that enroll children in any of grades K through 8 are asked to participate in the pediatric asthma surveillance program. Participation rates have increased throughout the project from 70% in 2002 to nearly 100% in the 2008-2009 school year.

What information is requested from schools?

Basic information is collected including name and address of the school and the number of children with asthma by gender and by grade. The city or town of residence for each child is also collected.  This data enables MDPH/BEH to estimate asthma prevalence by school as well as by city/town of residence.  No child-specific information that could identify a particular student is ever collected. 

What statistic is used to measure the amount of asthma in a school or community?

In this surveillance summary, prevalence is the statistic used to measure the amount of pediatric asthma in each school or community.  Prevalence in schools is defined as the percentage of enrolled students reported by school nurses to have asthma during a school year.  Prevalence in communities is defined as the percentage of students who are residents of the community and enrolled in a Massachusetts public or private school reported by school nurses to have asthma during a school year. School nurses gather this information from the student’s school health record, physician reports, and parent information forms.

How do I interpret prevalence estimates?

To determine if the prevalence in schools and communities is significantly different from the state rate or if the difference may be due solely to chance, a 95% confidence interval (CI) was calculated for each rate.  A 95% CI assesses the magnitude and stability of a rate.  Specifically, a 95% CI is the range of estimated prevalence values that has a 95% probability of including the true prevalence for the population. 

One method for determining if one prevalence estimate is statistically significantly different from another is by comparing the confidence intervals.  If the 95% CI for one community or population does not overlap the CI of another, then it can be concluded that the two populations are statistically significantly different from each other.  If they do overlap, then it can be concluded that the two populations are likely not statistically significantly different.  “Statistically significantly different” means that the difference observed between the rates will occur by chance less than 5 percent of the time.  For example, if the prevalence for community A is 5.6 with a 95% confidence interval of 4.8-6.4 and the state prevalence is 10.2 with a confidence interval of 10.0-10.4, when the two intervals are compared, the interval for community A does not fall within the range of the state confidence interval.  Therefore, it is concluded that community A’s prevalence estimate of 5.6 is statistically significantly different than the state rate of 10.2.  And because community A’s rate is lower than the state’s, it can be concluded that the community’s rate is statistically significantly lower than the state rate.   

What is the relationship between asthma and air pollution?

Acute asthma attacks can be triggered by indoor and outdoor air pollutants and allergens.  Twenty percent of the U.S. population, or nearly 55 million people, spend their days in elementary and secondary schools. In the mid-1990s, studies showed that 1 in 5 of the nation's 110,000 schools reported unsatisfactory indoor air quality, and 1 in 4 schools reported unsatisfactory ventilation, which has an impact on indoor air quality. Indoor air allergens include things like mold.  The outdoor air pollutant most commonly linked to asthma attacks are particulate matter and ozone.  The U.S. EPA Air Quality Index (AQI) is an index for reporting daily air quality.  The AQI tells you how clean or polluted your air is, and what associated health effects might be a concern for you. 

Are there certain caveats about the data to be aware of?

Yes. These data are for children in kindergarten through 8th grades only. It is important to note that community-based prevalence estimates are based on the residential location of the student, and not necessarily the location where an exposure took place. School-based prevalence estimates are based on all children attending that school, which may in some instances include students from multiple cities/towns. Prevalence is not age-adjusted and therefore when comparing prevalence estimates across communities, keep in mind that some of the observed differences in prevalence estimates may be due to differences in the age distribution of students in each community. Also please keep in mind that a variety of non-environmental factors, such as access to medical care, can impact the prevalence of asthma.

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