Childhood Asthma
Asthma is a chronic inflammatory disease of the airways. Asthma has been associated with a number of environmental pollutants including ozone, nitrogen and sulfur oxides, dust mites, second hand smoke, asbestos, and particulate matter (Etzel, 2003; Institute of Medicine, 2000). Although there are genetic factors which predispose people to the development of asthma, exposure to certain environmental factors may contribute significantly to the risk of developing the disease. Once somebody has asthma, exposure to certain environmental factors can increase the likelihood of suffering from attacks. Air pollutants in both indoor and outdoor environments are known contributors to asthma attacks (U.S. Environmental Protection Agency, 2007
Over the past decade, the prevalence of asthma in both children and adults has increased in the United States. Asthma prevalence in Oregon continues to rise and is considerably higher than the U.S. average of 7.2% (Moorman et al., 2007). Current asthma prevalence in 2005 was 9.9% in Oregon adults aged 18 or older and 8.4% in Oregon children less than 18 years of age (Oregon Department of Human Services [Oregon DHS], 2007). Accordingly, approximately 345,000 Oregonians currently have asthma, including almost 274,000 Oregon adults and nearly 73,000 Oregon children.
Following the methodology of Landrigan et al. and Massey & Ackerman, we estimate the environmentally attributable costs of adult and childhood asthma in Oregon.
Costs of Childhood Asthma
For asthma, Landrigan et al. did not derive their estimate of national asthma costs on a cost-per-case basis as they did with other diseases. Instead, they based their estimated costs of childhood asthma on an existing estimate of total national costs from the methods used by Chestnut, Mills, & Agras (2000) and Weiss, Gergen, & Hodgson (2000). Using these studies, Landrigan et al. estimated the total annual costs of childhood asthma to be $6.6 billion in 1997 dollars, comprising $4.6 billion in direct health care costs and $2.0 billion in indirect costs. Direct health care costs include inpatient, outpatient, and emergency room care, physician services, and medications. Indirect health care costs include lost school days and lost productivity due to premature death.
Massey and Ackerman (2003) use three methods to calculate the costs of childhood asthma in Massachusetts. One method is based on the costs of acute asthma hospitalization. A second method uses the costs of asthma in the United States Environmental Protection Agency’s Cost of Illness Handbook (U.S. EPA COI; p. IV.2-3) which estimates health care costs only. The third method, that of Landrigan et al., takes account of direct health care costs and indirect costs associated with lost productivity.
This study uses both Landrigan et al.’s method and Massey and Ackerman’s EPA-based estimate to calculate the costs of childhood asthma in Oregon.
Environmentally Attributable Factor Range (EAFR) and Best Estimate:
Landrigan et al. convened a panel of experts in environmental and pulmonary medicine to estimate the portion of childhood asthma attributable to environmental contaminants. The expert panel estimated that 10-35% of acute exacerbations of childhood asthma are related to outdoor, non-biologic pollutants from sources such as vehicle exhaust and emissions from stationary sources. Asthma exacerbation due to household allergens, molds, second-hand smoke, infections or climatic conditions were not included in the EAFR. Both Landrigan et al. and Massey and Ackerman used an EAFR of 10-35% for childhood asthma. Landrigan et al. used a best estimate of 30%.
Cost and Prevalence:
Following are two methods for calculating childhood asthma costs in Oregon. The first is based on the methods of Landrigan et al., and the second utilizes the methods of Massey and Ackerman.
i) Landrigan et al. method
This estimate of the costs of childhood asthma attributable to environmental contaminants in Oregon is based on the following assumptions:
- Oregon comprises 1.22% of the U.S. population;
- Estimate of total annual U.S. national costs of childhood asthma used by Landrigan et al. of $6.6 billion in 1997 dollars updated to $8.6 billion in 2007 dollars;
- Direct health care costs constitute 69.7% of total costs;
- Indirect health care costs constitute 30.3% of total costs; and
- An EAF of 30% with a range of 10-35%.
Annual costs of asthma in Oregon = $8.6 billion * 1.22% = $104.9 million in 2007 dollars.
Applying the EAFs of 0.10, 0.30, and 0.35 yielded the following results:
- EAF 0.10 = $10,492,000
- EAF 0.30 = $31,476,000
- EAF 0.35 = $36,722,000
Using these assumptions, the best estimate of the annual cost of childhood asthma attributable to environmental contaminants in Oregon is $31.5 million in 2007 dollars (comprising an estimated $22 million in direct health care costs and $9.5 million in indirect costs), with a range of $10.5-36.7 million.
ii) Massey and Ackerman method
Another method for calculating the cost of childhood asthma is to use the approach of Massey & Ackerman. In their Massachusetts study, Massey and Ackerman used the U.S. EPA Cost of Illness Handbook figures for annual costs per case, updated from 1999 dollars to 2002 dollars. Then they used Massachusetts’ prevalence data and the EAFs to calculate the annual cost of environmentally attributable fraction:
(prevalence, as # of cases) * (annual cost-per-case)* (EAF)
This estimate of the costs of childhood asthma attributable to environmental contaminants in Oregon is based on the following assumptions:
- 8.4% of all children (<18 years) in Oregon have asthma;
- 846,256 children (<18 years) in Oregon based on U.S. Census projections (U.S. Census);
- 71,085 children with asthma in Oregon;
- Annual costs = $1,105 per case; and
- A best estimate of 30% and an EAFR of 10-35%.
We then apply the annual cost-per-case data and figures from the U.S. EPA Cost of Illness Handbook (updated from 1999 dollars to 2007 dollars):
Annual cost-per-case for ages 4 to 5 years = $761.16 in 1999 dollars = $960.25 in 2007 dollars
Annual cost-per-case for ages 6 to 17 years = $904.90 in 1999 dollars = $1,141.59 in 2007 dollars
Since EPA’s estimates were separated into costs for ages 4 to 5 years and costs for ages 6 to 17 years, and the Oregon DHS current asthma prevalence is for all children less than 18 years, we averaged the costs out over the whole time period:
[($960.25 *2 years) + ($1,141.59 *12 years)]/(14 years) = $1,115.68 per case for ages 4 to 17 years.
We apply this as the estimated costs-per-case for all cases less than 18 years:
(71,085 cases)*($1,116 per case) = $79,330,860 total cost for all Oregon childhood asthma cases.
Using the EAFs of 0.10, 0.30 and 0.35 gives the following results:
- EAF 0.10 = $7,933,086
- EAF 0.30 = $23,799,258
- EAF 0.35 = $27,765,801
Using these assumptions, the best estimate of the annual costs of childhood asthma attributable to environmental contaminants in Oregon is $23.8 million in 2007 dollars with a range of $7.9-27.8 million.
Averaging the best estimates, the environmentally attributable costs of childhood asthma in Oregon are estimated at $27.65 million per year, with a range of $7.9 to $36.7 million.
