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* From the Department of Epidemiology and Preventive Medicine (Drs. Leigh and Schenker), School of Medicine, University of California at Davis, Davis, CA; the Department of General Medicine (Dr. Romano), University of California at Davis Medical Center, Sacramento, CA; and Division of Respiratory Disease Studies (Dr. Kreiss), National Institute for Occupational Safety and Health, Morgantown WV.
Correspondence to: J. Paul Leigh, PhD, Department of Epidemiology and Preventive Medicine, School of Medicine, TB 168, University of California at Davis, Davis, CA 95616-8638
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Abstract |
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 TOP Abstract IntroductionMaterials and MethodsResultsDiscussionConclusionReferences |
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Design: Aggregation and analysis of national data sets collected by the National Center for Health Statistics, the Health Care Financing Administration, and other government bureaus and private firms. To assess mortality, we reviewed data from national surveys and applied a population attributable risk (PAR) of 15% for both asthma and COPD. We use a lower age limit of 35 years for occupational COPD and 20 years for occupational asthma. To calculate costs, we use the human capital method that decomposes costs into direct categories, such as medical expenses, as well as indirect categories, such as lost earnings and lost home production. We calculated proportionately adjusted costs for other plausible PARs.
Results: The 15% PARs result in costs of $5.0 billion for COPD and $1.6 billion for asthma. For COPD, 56% of costs were direct and 44% were indirect; for asthma, 74% were direct and 26% indirect. These estimates are conservative since we ignored costs associated with pain and suffering as well as the value of care rendered by family members. The proportionately adjusted costs for 10 to 20% PARs are $3.3 to $6.6 billion for COPD and $1.1 to $2.1 billion for asthma.
Conclusions: The estimated $6.6 billion cost of occupational COPD and asthma in 1996 is likely to rise with the increasing prevalence of these diseases and warrants preventive intervention.
Key Words: asthma • COPD • economics • jobs • occupational respiratory diseases
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Introduction |
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TOPAbstractIntroductionMaterials and MethodsResultsDiscussionConclusionReferences |
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The National Heart, Lung, and Blood Institute4 estimated the cost of COPD to be $26 billion in 1998. Estimated direct costs accounted for $13.6 billion (52%) and indirect costs for $12.4 billion (48%). Asthma was estimated to cost $11.3 billion, with $7.5 billion in direct costs (66%) and $3.8 billion in indirect costs (34%).4 Earlier studies put the cost of asthma at $6.2 billion in 1990 dollars5 and $5.8 billion in 1994 dollars.6 COPD generates higher indirect costs than asthma because COPD causes more deaths than asthma.
Unfortunately, few estimates of the numbers of deaths and costs of occupational obstructive lung diseases are available.7 8 9 10 Costs can be used to assess the magnitude of the burden and to rank public-health initiatives in order of economic importance. Our purpose in this study is to generate estimates of deaths and costs that incorporate the best methods from prior studies. We use standard methods with some simple improvements, such as adjusting for the mix of costs between inpatient and outpatient care. As a result, our estimates may be compared to published estimates for other diseases (whether or not job related). We will also discuss how society at-large is likely to pay for a significant portion of these costs.
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Materials and Methods |
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TOPAbstractIntroductionMaterials and MethodsResultsDiscussionConclusionReferences |
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There are two methods of considering disease rates: incidence and prevalence. Since forecasting the future costs of incident cases requires heroic assumptions, we use the prevalence method to estimate annual deaths and costs of prevalent cases of COPD and asthma occurring in 1996. The prevalence method has been used in other published estimates of the cost of obstructive lung disease21 and measures the current economic impact of all prevalent cases.
There are no data available that unambiguously count the number of either occupational COPD or occupational asthma deaths. Although as many as 80 to 90% of COPD cases in the United States are frequently attributed to direct smoking,22 the etiologies of both asthma and COPD are multifactorial. Prior studies11–20 have attempted to determine the percentage of obstructive pulmonary disease deaths attributable to occupational hazards—the population attributable risk (PAR)—by estimating epidemiologic associations based on job exposures or occupations, or by identifying self-reported or physician-diagnosed cases of occupational lung disease. We assume, as prior authors11 12 13 14 15 16 17 18 19 20 have, that the prevalence of obstructive lung disease would drop by the PAR if occupational exposures were removed, recognizing that this assumption may be invalid due to biases, competing hazards, and the difficulty of assigning one cause in a multifactorial disease.
There is no consensus in the epidemiologic literature regarding the correct PAR for occupational factors that contribute to asthma and COPD. Becklake11 and Becklake and Ernst12 have published the most comprehensive review of studies on the PAR of occupational factors in COPD, selecting five population-based studies adjusted for age and smoking. These studies reported PARs of 2% (Norway), 14% (six US cities), 28% (male patients in Tucson, AZ), 14% (chronic bronchitis in Italy), and 16 to 18% (chronic bronchitis in France). We have selected a PAR of 15% for the United States, given this range, heavily influenced by the study by Korn et al23 of > 8,500 men and women in six US cities. We use linear (proportional) estimating techniques for deaths, hospital days, and costs so that the cost associated with any attributable fraction can be easily calculated.
Authors of Healthy People 201024 suggest that "occupational factors cause or trigger asthma episodes in 5 to 30% of adults with this disease." Blanc and Toren25 published a comprehensive review of 43 attributable risk estimates for occupationally associated asthma from 19 countries. The median PAR value for the 23 published estimates was 9% (range, 2 to 33%; interquartile range, 6 to 18%), whereas the median value for the eight PARs that Blanc and Toren25 derived from published data was 25% (range, 15 to 45%). The 12 studies extrapolating PARs from incidence data generated significantly lower estimates, with a median value of 5% (range, 1 to 17%). The 12 most methodologically sound studies, based on the number of subjects with asthma, the source of asthma diagnosis, determination of work-relatedness, study design and sampling method, adjustment for smoking, age at onset, and publication type, had a 15% median PAR estimate, which was also the median in the 10 studies that estimated the PAR from population-based samples. From these ranges, we have selected a 15% PAR for occupational asthma (in accord with a draft statement prepared by an ad hoc committee of the American Thoracic Society on PARs for both asthma and COPD) [John Balmes, MD; personal communication; December 2000].
An age restriction is necessary because children do not hold jobs and teenagers typically work part-time, if at all. We assume that no job-related COPD deaths or hospitalizations occur in persons < 35 years of age. More than 99% of COPD deaths and roughly 98% of hospitalizations occur in persons at least 35 years of age. For asthma, we do not count any deaths, hospitalizations, or costs in patients < 20 years of age. We use a younger age limit for asthma than for COPD because there is some evidence for job-related asthma even in teenagers.26 Given that (1) the great majority of teenagers do not work full-time, (2) many do not work outside the home at all, and (3) job turnover among teenagers is the highest of all age groups,27 we did not deem it appropriate to apply our PAR estimates to teenagers. We estimate that 5% of asthma deaths (298 of 5,667 deaths) and roughly 35% of all asthma-related hospital days are excluded by our age restriction.
We defined COPD based on a first-listed diagnosis of ICD9-CM codes 490 (bronchitis, "not otherwise specified"), 491 (chronic bronchitis), 492 (emphysema), 494 (bronchiectasis), or 496 (chronic airway obstruction, "not elsewhere classified"), using data from the National Hospital Discharge Survey and the Healthcare Cost and Utilization Project Nationwide Inpatient Sample. The definition of "other COPD and allied conditions" in the National Ambulatory Medical Care Survey and the National Hospital Ambulatory Medical Care Survey also includes 495 (extrinsic allergic alveolitis), so we were unable to exclude this condition from our estimate of outpatient costs. Fortunately, this code has "virtually no effect on the size and trend of the morbidity and mortality statistics for COPD."28 In accord with all prior studies using data from the federal government, we aggregated emphysema and chronic bronchitis, because these conditions often coexist, have similar causes, and are treated in very similar ways.29 In fact, official coding guidelines published by the American Hospital Association state that "since patients rarely fall neatly into a single category, and bronchitis and emphysema frequently coexist, the diagnosis of COPD, 496, is often used ... the coder is warned not to attempt a more specific identification."30 Because we lack confidence in our ability to distinguish these conditions using administrative data, we applied the same job-related PAR to each subtype of obstructive pulmonary disease: chronic bronchitis, emphysema, and all other types of COPD.
Economics
Costs are estimated using the human capital method, whereby two
broad categories are constructed: direct and indirect costs. Within the
direct category, there are medical expenses and administrative
expenses. Medical costs include payments to hospitals, physicians,
pharmaceutical companies, nursing homes, and vendors of medical
supplies, including oxygen. Insurance administration includes the cost
of processing claims, managing financial accounts, paying bills,
advertising, sales commissions, rate credits, prosecuting fraud,
dividends, and profits or losses. The administrative expenses are in
turn split into administration for medical and administration for
indemnity insurance.
Indirect costs include lost wages, lost fringe benefits, and lost home production. Lost wages are meant to capture not just the hardship for the person and family without the wages, but also the cost to the economy in terms of lost output. Lost fringe benefits are included for the same reason. Home production includes the time costs of child care, making home repairs, preparing meals, and so on. General discussions of the advantages and disadvantages of the human capital method are available.7
Direct Costs: Our "top-down" approach to estimating direct costs is similar to that of Rice et al.21 31 Our estimates rely on ratios involving hospital days multiplied by national estimates of medical spending (see equation 1 following). These hospital-day ratios act as anchors in the estimation of all direct costs. Hospitalizations are the most expensive broad category of medical care, responsible for 40% of medical costs in 1996. Doctors’ services are second at 22%.32 Most other cost studies assume that spending on all other direct costs is proportional to hospital spending.21 This assumption is controversial, especially for COPD and asthma. COPD frequently results in death, whereas asthma does not. Asthma typically requires considerable outpatient care, but hospitalization rates may be relatively low. We adjust for the inpatient/outpatient mix of costs, which represents an improvement over prior cost studies.7 21 31
Our top-down approach begins with an estimate of national expenditures on medical care: $1,035 billion or 13.6% of the gross domestic product in 1996.32 Medicare and Medicaid (including Medi-Cal) contributed 20.0% and 14.7%, respectively; other third-party government spending contributed 11.4%; direct out-of-pocket expenditures contributed 17.6%. The remainder, 36.3%, was contributed by private health insurance and health maintenance organizations. These $1,035 billion in health-care expenditures included payments for hospitalizations, physician visits, nursing home care, medications, medical supplies, and dental services, among other services. Although the estimate of $1,035 billion by Levit et al32 includes $60.9 billion for the cost of program administration and the net cost of health insurance, we believe that this estimate (6.3% of total health expenditures) is too low. Studies have shown that administrative costs can add up to 45% of the total cost of medical care.33 34 35 36 Danzon34 has been especially critical of the low estimates for Medicare and Medicaid. For example, private insurance companies require buffer funds that are captured in premiums, but may not be paid out as benefits during a given year. These buffer funds are sometimes viewed as wasteful administration, but they are not. Governments do not require buffer funds, because they can raise taxes to shore up public insurance programs, such as the Medicare Hospital Insurance trust fund.35 The 1994 estimate by Cutler36 of 15% appears to be reliable and widely used in previous analyses.7 10 As a result, we exclude the $60.9 billion estimate of Levit et al,32 but add a 15% administrative expense to our calculations. We also exclude dental services ($47.6 billion), reasoning that neither asthma nor COPD should influence dental costs.
Using the National Hospital Discharge Survey,37
we then
calculated the total number of days spent in the hospital by patients
with a principal diagnosis of COPD or asthma. To illustrate, suppose we
consider only COPD:
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The inpatient and outpatient adjustments are unique to this study. The hospital-days ratio in equation 1 assumes that all hospital days have equal costs, regardless of the disease. It also assumes that all nonhospital (outpatient) costs are proportional to hospital days, for all conditions.10 21 31 In fact, mean daily charges (and presumably costs) are about 16% lower for COPD hospitalizations, and 17% lower for asthma hospitalizations, than for the average US hospitalization.38 Furthermore, asthma is responsible for a relatively large share of outpatient care (eg, 1.33% of all physician visits in 1996 vs 1.07% of all hospital days), whereas COPD is responsible for a relatively small share (eg, 1.83% of all physician visits, vs 2.06% of all hospital days).39 40 Therefore, we adjust for these important differences using data on hospital days and physician visits from the National Center for Health Statistics,39 40 and data on hospital daily charges from the Healthcare Cost and Utilization Project of the Agency for Healthcare Research and Quality.38
The equation estimates do not account for administrative costs. To obtain administrative costs, we assume that (1) insurance companies and governments spent $803 billion on health care in 1996 (subtracting $171.2 billion in out-of-pocket expenditures from $974.2 billion in total nonadministrative expenditures); and (2) the average of private and public insurance administrative costs is 15%.36 We further assume that similar administrative costs apply to indemnity insurance (disability, Workers’ Compensation) administration, and that these indemnity payments average about 50% of a worker’s prior wages. Detailed calculations are available from the first author.
Indirect Costs: Indirect mortality costs were estimated using a standard present value equation.10 The present value equation used age-specific, sex-specific, life-table estimates and disease-specific mortality data from the National Center for Health Statistics, Vital Statistics Division,41 42 43 as well as earnings and labor force participation data from the Bureau of Labor Statistics.44
Finally, we calculated national disease-specific ratios for morbidity costs to direct costs from Rice et al21 to estimate the morbidity costs of occupational COPD and asthma. These estimates were, in turn, adjusted to reflect the fact that asthma causes many hospitalizations but few deaths. Whereas asthma accounts for roughly 25% of hospital days for all obstructive pulmonary diseases, it accounts for only 5% of deaths for all obstructive pulmonary diseases.
Indirect mortality costs capture wages, fringe benefits, and home production for years of life lost due to early death. Indirect morbidity costs capture the same three categories for persons who have not died, but are at least partially disabled due to obstructive pulmonary disease.
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Results |
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TOPAbstractIntroductionMaterials and MethodsResultsDiscussionConclusionReferences |
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Prevalence:
The National Center for Health Statistics provides
estimates of prevalence of obstructive disease.43
In 1996,
14,150,000 persons were estimated to have chronic bronchitis, 1,821,000
to have emphysema, and 14,596,000 to have asthma. If we assume that
15% of chronic bronchitis and emphysema cases are due to occupational
factors, then our prevalence estimate is 2,395,650 for chronic
bronchitis and emphysema combined (COPD). Although this estimate
ignores age, > 99% of COPD deaths occur in persons aged 
35
years. Whereas ignoring age may be inconsequential for chronic
bronchitis and emphysema, it is problematic for asthma because 35% of
asthma hospital days are among persons < 20 years of age. Adams et
al45
estimate 9,712,000 asthma cases among persons 20
years of age. Fifteen percent of this total is 1,456,800. As more solid
estimates of PAR are developed, revised estimates of prevalence can be
calculated by multiplying the above-mentioned estimates by the ratio of
the revised estimate to our 15% estimate. These prevalence estimates
are not used to estimate costs; hospital days are used instead.
Costs
Table 1
presents our estimates of the direct costs of COPD. Table 2
presents our estimates of the direct costs of asthma. Table 3
presents estimates of the indirect costs of COPD and asthma. Table 4
combines the more important estimates from Tables 1
2
3
, with the
total of direct plus indirect costs. Our estimates of total costs,
given a 15% PAR, were $5.0 billion for COPD, $1.6 billion for asthma,
and $6.6 billion for all obstructive pulmonary diseases combined. For
the 10 to 20% PAR range, the COPD costs ranged from $3.3 to $6.6
billion; the asthma costs ranged from $1.1 to $2.1 billion.
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Discussion |
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TOPAbstractIntroductionMaterials and MethodsResultsDiscussionConclusionReferences |
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18 years, was $1.2 billion for direct costs
and $1.3 billion for indirect costs. To compare these estimates to
ours, we must make several adjustments. First, the prevalence of asthma
has more than doubled among persons aged 18 to 44 years, and among
persons 65 years of age.2
It has increased nearly 50%
among persons aged 45 to 65 years.2
These increases
reflect a higher incidence of disease, as well as a larger population
at risk. Assuming an 80% increase in prevalence, averaging across all
age groups results in a corresponding 80% increase in costs from 1985
to 1996. Second, we must account for inflation. The consumer price
index for medical care, which applies to direct costs, increased
105.3% from 1985 to 1996.46
The employer cost index,
which applies to indirect costs, increased 42.7% from 1985 to 1996.
Thirdly, the estimate of Weiss et al5
for persons aged
18 years included only hospital and physician costs. These costs
constitute roughly 67% of nonadministrative medical
expenditures.32
Incorporating all three of these
adjustments, the adjusted estimate of Weiss et al5
of the
total cost of asthma in 1996 would be $9.9 billion ($6.6 billion for
direct costs, $3.3 billion for indirect costs).
If we assume that our 15% PAR ($1.6 billion) can be multiplied by 6.67
to generate an estimate for all asthma, whether or not job related,
then our 1996 cost estimate would be $10.5 billion. Given that our
estimate includes a higher insurance administration expense than Weiss
et al,5
and a slightly narrower age spectrum
(eg, 20 years vs 18 years), our total estimates are
remarkably similar. With these adjustments, the estimate by Weiss et
al5
of the ratio of direct to indirect costs, 67 to 33%,
is also comparable to our estimate of 74 to 26%.
Similar comparisons can be made with Smith et al,6 who estimated $2.9 billion of direct costs and $0.5 billion of indirect costs for asthma in 1987, across all ages. If we assume that the division of direct costs between adults and persons < 18 years of age (Weiss et al5 ) also applies to Smith et al,6 then the estimate by Smith et al of the direct cost of asthma among adults in 1987 would be $2.1 billion. We do not use the 1994 estimate of Smith et al,6 since it did not allow for increased disease prevalence from 1987 to 1994. If we assume a 70% increase in prevalence from 1987 to 1996 and a 78% inflation rate for medical care, then the direct cost estimate in 1996 by Smith et al6 would be $6.4 billion. This estimate is similar to the equivalent estimate of $6.1 billion by Weiss et al,5 as well as our direct cost estimate that excludes administrative costs ($6.8 billion = $1.0238 x 6.67).
The estimate of indirect costs by Smith et al,6 even with adjustments for increasing prevalence and inflation, is considerably less than ours and that of Weiss et al.5 Their relatively low indirect cost estimate is likely a result of their decision to exclude mortality costs and put a lower price on homemaker services than Weiss et al.5
Implications
The morbidity and mortality burden of occupational obstructive
lung disease is significant, with an estimated 15,837 deaths in 1996.
By comparison, 31,130 Americans died of AIDS; 20,971 were murdered; and
20,340 died of leukemia.1
The magnitude of occupationally
related asthma and COPD dwarfs statistics for coal workers’
pneumoconiosis mortality (1,417 deaths), asbestosis (1,176 deaths), and
mesothelioma (510 deaths).47
Second, the cost of job-related obstructive lung disease is significant: $6.6 billion in 1996 assuming a 15% PAR. This represents an important burden on the health-care system and a drain on the economy. Costs have become a critical factor in the national debate on the allocation of medical spending. Rarely, however, has that debate addressed job-related COPD and asthma.48
Thirdly, whereas some portion of the $1.6 billion cost of occupational asthma is likely paid by employer’s contributions to Workers’ Compensation premiums, the "lion’s share" of the $5.0 billion cost for COPD is paid by workers, their families, and taxpayers. Only infrequently do Workers’ Compensation systems pay for COPD, because the disease manifests itself commonly after retirement and is multifactorial in etiology. It is difficult to prove that the condition in an individual was caused by job factors. Most of the costs of medical care for COPD are likely to be borne by Medicare, ie, by taxpayers. A significant portion of the lost wages is likely to be paid for by the Social Security Administration, either through survivors’ benefits or disability benefits. Most economic studies of the Social Security payroll tax and the Medicare tax indicate that workers pay these employer taxes indirectly, in the form of lower wages.7
In summary, workers and taxpayers, not employers, bear the brunt of the costs of occupational COPD. In the language of economics, a negative externality exists. Employers are not paying for the true costs of production. They are shifting the costs to workers and taxpayers. Simple economic analysis49 shows that under these conditions, too much of the "negative externality" (ie, job-related COPD and asthma) will be produced by employers.
Limitations
There are a number of limitations to our study. First, deaths and
hospital days were counted as occurring in 1996. However, the exposures
leading to these deaths and hospitalizations could have occurred 20 or
30 years earlier. Death rates due to obstructive lung disease have been
increasing for 20 years. Moreover, the labor force grows virtually
every year. These limitations suggest that the true cost of
occupational obstructive lung disease may grow in the future. However,
we have little information regarding whether workplace exposures
associated with COPD and asthma have changed over the last 20 years;
any changes could affect the future burden of chronic obstructive lung
disease. The methods and estimates for the 1996 burden of occupational
COPD and asthma will likely prove useful to future researchers.
Another limitation of this study is that ICD9-CM codes cannot effectively distinguish between different subtypes of COPD, such as chronic bronchitis and emphysema. Following the methodology of earlier "cost of illness" studies,21 we relied on ICD-9-CM codes to define illness. We therefore included code 492 (emphysema) with codes 490 and 491 (chronic bronchitis), as well as codes 494 through 496 (other COPDs). Unfortunately, the estimates for specific subtypes are unreliable. For example, among deaths, chronic bronchitis contributed 3%, emphysema contributed 17%, and all other COPDs contributed 80%. For days of hospitalization, chronic bronchitis contributed 70%, emphysema contributed 7%, and all other COPDs contributed 23%.
If one subtype is more strongly associated with occupational factors than any other, and this subtype is also more or less costly than average, then our estimates of the cost of occupational COPD may be biased. However, there is no empirical evidence that any single subtype of COPD is more strongly associated with occupational exposures than any other. For example, Becklake11 reported odds ratios of 1.0 to 2.1 for chronic bronchitis (across five studies) and odds ratios of 1.4 to 2.3 for COPD (across four of the same studies). Therefore, this limitation is unlikely to be a major source of bias.
Our cost estimates depend on the assumed PAR. There is controversy
surrounding which PAR is most relevant to the US population, which we
have partially addressed by restricting attention to persons aged
20 years for asthma, and aged 35 years for COPD. We used linear
estimating techniques so that alternative PARs can be applied, if
future evidence suggests that a higher or lower PAR is more accurate.
If we assume that the PAR for smoking is 80%,22 then a 15% PAR for occupational factors suggests that occupational exposures account for 75% of all COPD not caused by smoking. PARs for different factors are likely to sum to > 100% because of synergistic effects. In our case, for some people, both occupational dust exposure and smoking would be required to cause COPD. If either one were eliminated, some persons would not develop COPD.50 51 Synergistic effects on lung cancer are well documented for asbestos and smoking.52 The presence of synergistic effects would imply that > 20% could be allocated to nonsmoking causes, assuming an 80% PAR for smoking.
Finally, our PAR estimates for both COPD and asthma ignore the possible impact of occupation on smoking patterns and quitting rates. But social and psychological pressures within certain occupations may discourage people from quitting. Among women, waitresses, bus drivers, assemblers, and laborers historically have been heavy smokers.53 Among men, meat cutters, auto mechanics, truck drivers, police officers, and laborers historically have been heavy smokers.53 Attributable risk proportions that ignore these psychosocial patterns likely underestimate the deaths and costs associated with job-related COPD and asthma.
There are additional limitations. We did not adjust for current employment status in the present value of earnings tables. We merely adjusted for the labor force participation rate. In doing so, we modestly undervalued the earnings of those currently employed, because those currently employed are not a random sample of all persons in the labor market. In fact, currently employed persons probably have better lifetime employment prospects than the average of all persons in the labor force, because the latter group includes unemployed persons. This limitation suggests that we underestimated indirect costs.
We ignored costs due to pain, suffering, and impaired quality of life, because it is so difficult to estimate these costs. Lawsuits involving nonfatal injuries almost always involve some payment for pain and suffering. A "rule of thumb" frequently cited in the courts is that the value of pain and suffering equals three to four times the sum of medical expenses and lost wages.54 A variety of willingness-to-pay methods have been developed to estimate the costs of pain and suffering, but there is no consensus regarding the best method to use for occupational illnesses. Although some economists have argued that workers in dangerous occupations receive a wage premium that reflects their willingness to pay to avoid the associated risks, the size of this wage premium may not reflect the actual level of risk.7 This limitation suggests that we significantly underestimated true costs.
We did not include the costs of family caregivers’ time, nor the costs of health problems that occur among caregivers. These costs are undoubtedly large, but are difficult to estimate. Covinsky et al55 documented the deleterious physiologic, psychological, and economic consequences on spouses who provide care. One highly regarded study56 estimated that family ("informal") caregiving comprises 20% of direct costs. This figure would add $0.8 billion to our combined estimate for asthma and COPD, using a 15% attributable risk. We also excluded indirect costs to employers for hiring and training new workers to replace those who die or experience long absences.
Despite these limitations, there are unique merits to our approach. With the exceptions noted below, we used standard cost-of-illness techniques. Consequently, our estimates can be compared to other cost-of-illness estimates for COPD, asthma, and all other diseases and injuries. Some of our methods improve on prior estimates, by excluding dental services, adjusting for the relative mix of inpatient and outpatient care, which varies across conditions, and adjusting for the varying resource intensity of hospital care across conditions. Because these characteristics are likely to differ for other diseases, we recommend that this method be used in other studies of the cost of illness. Finally, we did not rely on the National Center for Health Statistics32 estimates for program administration, which have been sharply criticized by economists34 36 and ignore the cost of insurance administration for indemnity benefits.
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Conclusion |
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TOPAbstractIntroductionMaterials and MethodsResultsDiscussionConclusionReferences |
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Acknowledgements |
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Footnotes |
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Support was provided by National Institute for Occupational Safety and Health Purchase Order Number 0009952162, and grant No. U07/CCU906162.
Received for publication February 24, 2000. Accepted for publication June 28, 2001.
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This article has been cited by other articles:
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 P. Cullinan, S. Tarlo, and B. Nemery The prevention of occupational asthma Eur. Respir. J., November 1, 2003; 22(5): 853 - 860. [Abstract] [Full Text] [PDF]
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 E. Hnizdo, P. A. Sullivan, K. M. Bang, and G. Wagner Association between Chronic Obstructive Pulmonary Disease and Employment by Industry and Occupation in the US Population: A Study of Data from the Third National Health and Nutrition Examination Survey Am. J. Epidemiol., October 15, 2002; 156(8): 738 - 746. [Abstract] [Full Text] [PDF]
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