Massachusetts Department of Public Health seal Massachusetts Environmental Public Health Tracking

Frequently Asked Questions - Chronic Obstructive Pulmonary Disease (COPD)

What is COPD hospitalization tracking?

COPD hospitalization tracking, or surveillance, is the ongoing collection, analysis, and interpretation of hospitalization data for COPD. The Massachusetts Environmental Public Health Tracking (MA EPHT) Program uses data on hospital admissions due to COPD to reflect the public health burden of the disease.

Why is the MA EPHT Program tracking COPD 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 indoor and outdoor environmental exposure and COPD suggesting that environmental exposure could be driving a large percentage of COPD cases.

COPD hospitalization measures can be used to monitor trends over time, identify high-risk groups, and enhance prevention, education, and evaluation efforts. Also, concerned community members can view the annual rate of COPD hospitalizations and the burden of COPD in their community or county.

What is the relationship between COPD and indoor / outdoor air pollution?

The most common indoor air pollution exposure are from smoke from tobacco and the use of biomass fuels (e.g., wood, crop residues, and coal for indoor uses such as cooking, lighting and heating).  The most common non-occupational outdoor air pollution exposure are from particulate matter (PM10 & PM2.5), ozone, and sulfur dioxide from automobiles and industrial sources.  Studies have also shown associations with occupational exposures such as fumes, gases, and both inorganic and organic dusts.

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 is occurring in a population. An age-specific rate for COPD is calculated for each age group to show how the incidence of COPD changes with age. A crude rate for COPD is the number of COPD admissions/ED visits 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.

What is a confidence interval?

To determine if prevalence 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, the interval for community A does not fall within the range of the state confidence interval when the two intervals are compared. Therefore, it is concluded that community A’s prevalence rate of 5.6 is statistically significantly different than the state estimate of 10.2. And because community A’s is lower than the state’s, it can be concluded that the community’s rate is statistically significantly lower than the state rate.

What are limitations of the data?

  • COPD rates are based on age groups most affected by this disease, so rates are only calculated among people 25 years of age and older on this site.
  • These measures are based on events not individuals.
  • Data are 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, excludes individuals who do not receive medical care or who are not hospitalized, including those treated in outpatient settings and those who die in emergency rooms, in nursing homes, or at home without being admitted to a hospital.
  • 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 are included in these measures.
  • 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 and diet, can impact the likelihood of persons hospitalized for COPD.
  • Differences in rates by time or area may reflect differences or changes in diagnostic techniques and criteria and in the coding of COPD cases.
  • Prevalence is based on the residential location of the cases.
  • 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.
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