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(Chest. 2002;122:1994-2002.)
© 2002 American College of Chest Physicians

Costs of COPD in Sweden According to Disease Severity*

Sven-Arne Jansson, BSc; Fredrik Andersson, PhD; Sixten Borg, MSc; Åsa Ericsson, PhD; Elsy Jönsson, MSc and Bo Lundbäck, MD, PhD

* From the OLIN Studies, Department of Medicine (Dr. Jansson), Sunderby Central Hospital of Norrbotten, Luleå; Department of Respiratory Medicine and Allergy (Dr. Jönsson), University of Umeå, Umeå; AstraZeneca R&D (Drs. Andersson and Ericsson, and Mr. Borg), Lund; and Unit for Lung and Allergy Research (Dr. Lundbäck), National Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden.

Correspondence to: Bo Lundbäck, MD, PhD, Unit for Lung and Allergy Research, National Institute of Environmental Medicine, Karolinska Institutet, SE-171 77 Stockholm, Sweden; e-mail: bo.lundback{at}telia.com


   Abstract
TOP
 Abstract
Introduction
 Materials and Methods
 Results
 Discussion
 Appendix 1
 References
 
Objectives: COPD is a common and disabling disease that entails high costs for society. The objectives of this study were to measure the societal costs of COPD in Sweden, and to examine the relationship between severity of illness and costs.

Methods: The costs of COPD were examined using a well-defined and representative cohort of subjects with mild, moderate, and severe COPD. Regular telephone interviews regarding resource utilization were made to a cohort of 212 subjects with COPD derived from studies of the general population in Northern Sweden.

Results: The annual per capita cost for COPD in Swedish crowns (SEK) was estimated at SEK 13,418 (1,284 US dollars (USD); 1,448 euros (EUR). The direct and indirect costs were SEK 5,592 (42%) and SEK 7,828 (58%), respectively. A highly significant relationship was found between severity of disease and costs. Costs for severe disease were 3 times as high as costs for moderate disease and > 10 times as high as for mild disease. Large individual variations in the level of costs were found.

Conclusion: Assuming that the prevalence and treatment patterns are representative of Sweden as a whole, the total costs of COPD to society in 1999 were estimated at SEK 9.1 billion (USD 871 million; EUR 982 million). Subjects with mild disease (83%) accounted for 29%, while subjects with moderate disease (13%) accounted for 41% of the total costs. The subjects with severe disease (4%) accounted for the remainder (30%). Prevention, early diagnosis, and postponement of disease progression should have large monetary and policy implications.

Key Words: COPD • cost of illness • severity • Sweden


   Introduction
TOP
 Abstract
 Introduction
Materials and Methods
 Results
 Discussion
 Appendix 1
 References
 
COPD is a common disease. The main risk factors are increasing age, which expresses a "total lifetime exposure," and smoking.1 2 3 4 With increasing age, an increasing proportion of smokers acquire the disease.3 4 5 6 7 COPD in most cases is marked by slow progression and is irreversible and chronic. Moderate-to-severe COPD is a disabling disease causing impairment in health-related quality of life for the patients8 9 and entailing high costs for society.10 11 In a Dutch study, the direct costs for COPD and asthma were estimated to represent 1.3% of the Dutch health-care budget in 1993,11 while in Sweden the total costs were estimated at approximately 1% of the costs for all diseases.12

Despite the existence of extensive literature on COPD, there is a lack of data on age-related, prevalence-based studies of the general population. According to population studies from northern Europe, the prevalence of COPD is low in persons < 45 years old.3 5 6 From the age of approximately 50 years, it increases considerably, particularly among smokers, and sooner or later >= 50% of smokers acquire it.3 4 However, the great majority of all persons with COPD have a mild form of the disease.3 5 13 With increasing age, the proportion of those with severe disease goes up.3 13 Despite this heavy burden, only a few health economic studies have been published based on data for COPD in the general population.10 11 12 14 15

Cost-of-illness studies examine the economic impact of illness on society. The costs are generally divided into direct and indirect costs.16 Direct costs refer to medical care in the form of prevention, diagnostics, treatment, and rehabilitation, etc. Indirect costs consist of the loss of productivity, which has an effect on society due to days off from work, early retirement, and death caused by the disease. When measuring the cost of illness, two different approaches can be used, the prevalence approach and the incidence approach.17 The prevalence approach, which was used here, estimates the costs of a disease during a 1-year period, while the incidence approach measures costs in a lifetime perspective.

The aim of this study was to estimate and analyze the societal burden of illness for COPD and to examine the relationship between the severity of the disease and the costs to society. The study also aimed to investigate which costs were key cost drivers in different segments of the COPD population.


   Materials and Methods
TOP
 Abstract
 Introduction
 Materials and Methods
Results
 Discussion
 Appendix 1
 References
 
In this study, the prevalence approach was chosen due to the considerable changes in treatment patterns that are expected to occur in the future. Data were collected by telephone interviews with a well-defined, representative cohort of subjects with COPD. The study was approved by the Ethics Committee at the University and the University Hospital of Northern Sweden in Umeå.

Study Population
Large-scale studies on the epidemiology of obstructive airways diseases and type-1 allergy in Northern Sweden, the Obstructive Lung Disease in Northern Sweden (OLIN) studies, started in 1985.18 19 20 Today, longitudinal studies of a number of cohorts are underway, including a total of approximately 40,000 children, adults, and elderly persons.21 22 The first survey of the second cohort of the OLIN studies included pulmonary function tests performed from 1993 to 1995 on 1,900 subjects born in 1925–26, 1940–41, 1955–56, and 1970–71.23 The third survey of the first cohort of the OLIN studies was performed in 1996–98 and included lung function tests performed on 2,600 subjects in three age cohorts: persons born in 1919–20, 1934–35, and 1949–50.3 24 The study cohort in the current study was derived from these two surveys and comprised subjects classified as having COPD.

COPD was defined according to the British Thoracic Society criteria,25 which divides COPD into mild, moderate, and severe disease (Table 1 ). In addition, persons with an FEV1/vital capacity ratio < 70% and an FEV1 >= 80% of the predicted value, which corresponds to the Global Initiative for Chronic Obstructive Lung Disease criteria for mild COPD,26 were also included in the study. Subjects with other diseases that explained their impaired pulmonary function were excluded. Subjects with chronic airways obstruction who referred to themselves as asthmatics were also included, an approach which is supported by the British Thoracic Society guidelines.25


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  		Table 1.. Participants by Age, Gender, and Severity of Disease

 
The above-mentioned OLIN studies23 24 include approximately 800 subjects with COPD; however, when stratifying by age (range, 28 to 80 years) and disease severity, some strata contain a limited number of subjects. Accordingly, all subjects with an FEV1 < 60% of predicted values were included in the present study cohort. In the case of subjects with an FEV1 >= 60% of the predicted value, a random sample was drawn from each stratum in order to obtain a study cohort of a sufficient size to allow measures of significant differences between different groups of severity. By subsequently assigning weights based on prevalence to our strata, bias originating from the selection could be avoided, since the weighted strata generated the weighted results according to the prevalence of subjects with corresponding age and degree of severity. The study population is shown in Table 1 .

Study Sample
Of the 261 subjects selected, 212 subjects (43% women) were interviewed. For various reasons, 38 persons could not be contacted, ie, they were not living at the given address, could not be reached by telephone, or did not speak Swedish, while 11 individuals refused to participate in the study (Table 2 ). The 49 persons in the original study sample who did not take part in the study did not differ from the 212 participating subjects in terms of age, gender, smoking habits, area of residence, or FEV1 (Table 2) .


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  		Table 2.. Demographics of the Study Sample and Nonparticipants*

 
Methods
A questionnaire was developed to record COPD-related resource use. Before the interviews took place, a letter was sent to the patients with information about the study. Telephone interviews were carried out with each respondent on four occasions in 1999 (March, June, September, and December). Each interview retrospectively covered resource use for a period of 3 months, December 1998 to February 1999, March to May 1999, June to August 1999, and September to November 1999. A period of 3 months was considered a suitable time in order to avoid recall bias.27 28 During the last 9 months of the 12-month study period, a patient diary was used to support the subsequent interviews with the aim of minimizing the risk of recall bias. Each interview lasted 10 to 45 min and was carried out by the same person (S.A.J.). Three attempts were made to reach each respondent.

A total of 201 patients were interviewed on all four occasions, 5 patients died during the study, and another 6 patients did not complete all the interviews. Costs for those who did not complete the study were estimated as the average costs for their previous study periods, according to the "patient-year approach" method.29 Patients who died during the study were assigned zero costs after death, since the official cause of death was not known when the study was carried out (only costs due to death caused by COPD were to be included in the analysis); however, these costs amounted only to a small proportion of the total costs in another Swedish study, based on register data.12

Costs
The costs were divided into direct and indirect costs. The direct medical costs included costs for hospitalizations, drugs, planned and acute health-care visits and contacts, oxygen therapy, and equipment used as aids, such as wheelchairs. The direct nonmedical costs included costs for moving to new quarters, home adaptations and education, or an occupational change. The indirect costs included loss of productivity due to absence from work and disability pensions. The costs were analyzed for the whole study population and for the subgroups of patients with mild, moderate, and severe disease. Only costs related to COPD were included. Exchange rates were USD 1 = SEK 10.4525, EUR 1 = SEK 9.2680, as of January 23, 2002.

Unit Costs
The costs for one day of intensive care in hospital were estimated at SEK 5,440,30 and the other unit costs for health-care resources in 1999 were obtained from the county council in Norrbotten, Sweden, where all patients lived (Table 3 ). Drug prices were obtained from the 1999 Swedish Pharmacopoeia,31 and the unit costs for oxygen therapy were estimated as the total monthly costs for an oxygen concentrator prescribed by Sunderby Central Hospital of Norrbotten, Luleå.


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  		Table 3.. Unit Costs for Health Care Contacts (SEK, 1999)

 
Indirect costs were measured as the value of potential productivity loss based on the human capital approach. Average pay, including payroll tax, was used to calculate the cost of each day absent from work. This approach offers a conceptual basis for valuing time costs and is the one most commonly used today.32 By this means, only market-related lost productivity is taken into account in the analysis. The unit cost for absence from work was estimated as the average salary in Sweden in 1999, including payroll taxes and social security contributions (SEK 1,129).33 Costs for disability pension were estimated as the costs for absence from work every working day based on the percentage of the disability pension (100%, 75%, etc). A month was assumed to consist of 22 working days.

Analysis
Since a societal perspective has been used, both direct and indirect costs were measured and valued. Costs for each subject were estimated, together with the mean cost for each category of severity of COPD. As a means of testing the influence of degree of severity on costs while controlling for covariates, multiple linear regression was applied with direct and total costs as dependent variables. Since the disease severity classifies subjects into four ordered groups with six possible comparisons, this regression approach is a straightforward way to perform the task of analyzing the dependency between FEV1 and costs. Due to the skewness of cost data, different transformations were used, namely no transformation and log-transformation. The model for direct costs examined 100% - FEV1 percent predicted, 100% - FEV1 percent predicted squared, and controlled for the following explanatory variables: age, gender, quantification of cigarette smoking (pack-years), presence of other airways disease diagnoses, presence of any nonairways-related disease diagnoses (yes/no), and population density in area of residence. The model for total costs also controlled for age at retirement to handle the discrete nature of indirect costs. In addition, each separate cost component alone was subjected to the same analysis. The sole purpose of these models was to analyze the relationship between costs and lung function, ie, none of these models were used for predicting costs.

The prevalence of each category of severity in Sweden was estimated using pooled data from the OLIN studies on the prevalence of COPD3 23 24 in combination with the composition of the Swedish population.33 By combining the prevalence of each category of severity of disease with the associated cost estimates, the total costs for all persons in Sweden with COPD were estimated, together with the costs per person with COPD. A 95% confidence interval (CI) for the total costs was estimated using a bootstrap, where prevalence data and cost data were resampled simultaneously and the estimation procedure was applied to each resample.34


   Results
TOP
 Abstract
 Introduction
 Materials and Methods
 Results
Discussion
 Appendix 1
 References
 
Resource Use
There were large variations in resource consumption depending on disease severity. Patients with severe COPD consumed considerably more health-care resources and drugs compared to patients with moderate or mild disease (Table 4 ). Large differences in disability pensions and absence from work due to COPD were also found in the different categories of disease severity.


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  		Table 4.. Average Annual Resource Consumption per Patient With COPD According to Severity of Disease

 
Total Costs
The societal costs, split into different cost items according to disease severity, are shown in Table 5 . The annual total costs were estimated at SEK 13,418 per subject with COPD. The direct costs accounted for 42% of the total costs. For all severity categories except the group with an FEV1 >= 80% of predicted value, the indirect costs were higher than the direct costs. The costs for a patient with severe disease were approximately 3 times as high as costs for a patient with moderate disease and > 10 times as high as for a patient with mild disease (Table 5) .


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  		Table 5.. Average Annual Societal Costs Per Patient With COPD According to Severity of Disease (SEK, 1999)

 
The total costs differed significantly between severity groups, patients with lower FEV1 percent of predicted normal being significantly more expensive (shown in Appendix). Apart from being dependent on disease severity, the total costs had a skewed distribution, with most subjects being moderately costly and a few very costly. This is indicated by the relatively low median values in the severity groups compared to the averages. A log transformation of the total costs did not improve the model fit, adjudging from the residuals.

Direct Costs
The annual direct costs were estimated at SEK 5,592 annually per person with COPD. The costs for persons with severe disease were 3 times greater than the costs for those with a moderate disease and more than 10 times as high as for those with mild disease. The main cost drivers among direct costs were drugs (40%) and hospitalizations (37%). Drugs and costs for health-care visits and contacts were the main cost drivers in mild disease, while hospitalizations were the main cost drivers in moderate and severe disease.

The distribution of direct costs according to disease severity is shown in Figure 1 . The direct costs differ significantly between severity groups, patients with greater loss in predicted percent FEV1 being significantly more expensive (shown in Appendix). The distribution of direct costs was skewed in a similar way to the distribution of total costs. A log transformation did not improve the model fit, adjudging from the residuals.



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  		Figure 1.. The percentage distribution of direct costs in the different groups of severity.

 
The average medication costs were SEK 2,238 per person. Subjects with FEV1 < 40% of predicted used more drugs. The average total costs for hospitalizations were SEK 2,066 per person. Those with severe disease had more days in hospital than persons with moderate or mild disease. Twenty-one percent of patients with FEV1 < 40% of predicted were hospitalized for at least 1 night, compared with 5%, 1%, and 0% for patients with FEV1 40 to 59%, 60 to 79%, and > 80%, respectively. Drug utilization was one of the primary reasons why severe disease resulted in higher costs than moderate or mild disease. For severe patients, drug and hospitalization costs were positively correlated (p = 0.0005). However, patients with mild-to-moderate disease had too few hospitalizations to make any conclusions about correlation possible. The total costs for planned and acute health-care visits and contacts were SEK 1,027 per person.

Equipment aids such as wheelchairs were only used by a few individuals, and thus the costs for equipment aids were only SEK 146 per person. A few individuals used oxygen therapy, and these costs were SEK 116 per person. The costs for home adaptations and for education or occupational change turned out to be zero. Only one person had removal costs, generating an average cost of a few SEK.

Indirect Costs
The annual indirect costs were estimated at SEK 7,828 per person with COPD. The main cost driver among the indirect costs was loss of productivity due to disability pension, for which annual average costs were SEK 7,079 per person, or 90% of the indirect costs. It is difficult to compare differences between groups due to the correlation between age and severity. The costs for disability pension were considerably greater than the costs for absence from work in all the severity categories, except in the group having FEV1 >= 80% of predicted, and ranged between 88% and 97% of total indirect costs in these categories.

A number of patients, 7.4%, had to stay home from work due to their COPD on some occasions during the year. The average societal costs due to loss of productivity were estimated at SEK 749 per person. Persons with severe disease had more days away from work and consequently the highest average costs (SEK 3,150). Primarily due to high age, only few persons with moderate-to-severe COPD were employed (6% and 10%, respectively). The corresponding rates for persons with an FEV1 of 60 to 79% of predicted and >= 80% of predicted were 39% and 43%, respectively.

Costs for Persons With Self-Reported Asthma
In the study sample, 78 persons (37%) had referred to themselves as having asthma. Of these 78 individuals, some of whom may have had two diseases (asthma and COPD), 55 subjects (71%) had FEV1 values < 60% of predicted. These patients had somewhat more hospitalizations, greater drug consumption, and a slightly larger number of disability pensions. This difference is most likely due to the fact that a greater proportion of these patients (71%) had moderate-to-severe disease as compared with 47% for the whole study sample. Furthermore, the variable "asthma" was nonsignificant in the linear models for costs.

Costs to Society
With an estimated prevalence of 678,494 persons (95% CI, 593,751 to 764,484),3 23 24 33 the estimated annual total cost to Swedish society is SEK 9.1 billion (USD 871 million, EUR 982 million; 95% CI SEK, 6.1 to 12.8 billion), 3.8 billion in direct costs and 5.3 billion in indirect costs. The costs were skewed in the present study, with mild disease accounting for 29% of the total costs and comprising 84% of the subjects (the two mildest groups), while moderate disease accounted for 41% of the total costs and comprised 13% of the subjects. The costs for those with severe COPD accounted for approximately 30% of the total costs and comprised approximately 4% of the individuals with COPD.


   Discussion
TOP
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
Appendix 1
 References
 
Knowledge about the cost of different diseases is useful in planning and accomplishing relevant health-policy interventions. COPD is a disease with highly skewed costs, and to get the full picture of it, it is important to study the costs for patients with varying severity of the disease. Only a few studies have investigated the correlation between disease severity and costs,35 36 37 38 and no previous study has analyzed total costs for each category of disease severity.

This study analyzed the costs of COPD from both a societal and a health-care payer perspective, using total and direct costs, respectively. Costs were analyzed at an individual level for patients with different degrees of severity of the disease and aggregated to the level of the Swedish society by the estimated prevalence of the disease, divided into different categories of disease severity.

There was a positive relationship between the degree of severity of disease and health-care costs. For patients with severe COPD, there was also a correlation between pharmaceuticals and hospitalization costs, indicating that both types of costs increase when the disease is becoming more serious.

The key cost drivers among the direct costs were costs for drugs (40%) and hospitalizations (37%). From the limited data available from other countries, it is clear that hospitalization is the most important cost driver among the direct costs, while drug costs are mostly a relatively minor cost driver.10 11 14 Another important difference concerning the distribution of the direct costs is the cost for oxygen therapy, which amounted to only 2% of the direct costs, this number being 18% in a study in the United Kingdom39 and 35% in the United States.14 These differences probably mainly reflect differences in the composition of the samples studied and country-specific treatment patterns.

The total per capita annual costs in this study were estimated to be USD 1,284, of which the direct costs accounted for 42%, or USD 535. The total costs for COPD in the United States in 1993 were estimated at USD 1,522 per person with COPD, of which the direct costs accounted for 62%.40 Wilson et al15 estimated the 1996 direct costs at USD 896 per COPD patient. A study performed in the Netherlands estimated the direct costs per patient in 1993 to be USD 876 per patient with COPD.11 Costs are comparatively low in Sweden.

The costs of pulmonary rehabilitation and surgery were not included in this study. However, pulmonary rehabilitation is still uncommon in Sweden, and from a perspective of COPD in the general population, the costs for COPD rehabilitation are limited. That is also true for costs of surgery for emphysema, which indeed are high for the few cases, but very limited from a general population perspective.

The only study previously performed in Sweden estimated the total costs for COPD in 1991 at SEK 2.8 billion (USD 268 million, EUR 302 million) by using register data.12 Direct costs were SEK 1.1 billion (USD 105 million, EUR 119 million, 39%), and indirect costs were SEK 1.7 billion (USD 163 million, EUR 183 million, 61%), showing a similar distribution of the costs into direct and indirect costs as in the present study (42% and 58%, respectively). The lower costs in that study could be explained by the study design. It is well known that there is a considerable underdiagnosis of COPD.18 23 The diagnosis of COPD has not been made in the majority of persons who actually have the disease. When using register data, correction for underdiagnosis cannot be made. Furthermore, in 1991, drugs prescribed for asthma were supplied free of charge to the patient, unlike those prescribed for COPD. This provided an incentive to report the diagnosis as asthma rather than COPD, since the same drugs could be used to treat the inflammatory component of the two diseases. Also, the present study was performed 10 years later, and the costs have risen during the last 10 years as COPD has become more visible.

Another important factor that may have lead to higher costs in the present study could be the fact that the geographic area studied, Norrbotten, has the highest proportion of disability pensions in Sweden.41 In 1999, the proportion of persons in Norrbotten with disability pensions was 9.4%, compared with 7.7% in Sweden as a whole. Respiratory diseases accounted for 3% of all reasons for early retirement in Norrbotten, while the mean value was 2% in Sweden as a whole. Disability pensions as a result of COPD accounted for approximately one half of the total costs and 91% of the indirect costs for COPD in the present study. This discrepancy only applies to disability pensions and, if also true of COPD subjects, would affect the results in that the average total cost per patient would be reduced from SEK 13,418 to SEK 12,138. Hence, the total annual cost to the Swedish society would thus be reduced from SEK 9.1 billion to 8.2 billion. However, there are no data to support the view that clinical treatment patterns of COPD may be different in this part of Sweden.

A few studies have analyzed the relationship between severity of COPD and costs,35 36 37 38 and even fewer have included all cost items in the analysis. However, a study in the United States found a similar relationship between disease severity and costs of COPD,35 as in the present study. In contrast to this study and studies by others,35 37 38 Decramer et al36 did not find any relationship between FEV1 and health-care expenditures. However, the latter study included only severe COPD, while the others included moderate COPD as well, and there is probably no relationship between FEV1 and costs within a class of severity, while the relationship exists when analyzing patients with a wider range of lung function.

The total costs for COPD in Sweden were estimated by multiplying the prevalence of COPD, weighted by severity, with the individual costs from this study. The estimated prevalence of COPD in Northern Sweden was assumed to be representative for Sweden. Prior to the results from the OLIN studies,3 there were no prevalence data for COPD in Sweden related to disease severity. Other than the OLIN studies, prevalence rates for COPD based on pulmonary function measurements have only been reported in one study in Sweden,6 where a prevalence similar to that in the OLIN studies was found. However, bronchitic symptoms are related to COPD.3 5 6 7 Comparisons of prevalence rates for bronchitic symptoms and chronic bronchitis thus roughly reflect differences in prevalence for COPD. Swedish questionnaire data have not shown any large differences in prevalence rates of bronchitic symptoms in different parts of Sweden, and smoking habits in the study were similar to the average for Sweden.6 19 21 Thus, one can assume that in Sweden as a whole, and in northern Sweden, the prevalence of COPD and also the prevalence rates of different categories of disease severity are similar.

There are both advantages and disadvantages with interview-based studies. The data collected are more detailed compared with the data from register studies and the risk of selection bias and underestimating costs is reduced because it is possible to "coach" the patient. However, there is still a risk of recall bias. Another disadvantage in using individual interviews may be that the study will be based on too few patients, which may result in samples with questionable representation.

Several studies have shown that there is a risk of recall bias in patients’ self-reports.27 28 In this study, various ways to minimize this risk were used. The patients underwent structured interviews on four occasions, each interview covering a period of 3 months. During 9 months of the 12-month study, a patient diary was used to minimize the risk of forgetfulness. Regarding drug utilization, the patients were asked to bring their medications to the telephone in order to ensure that the correct doses and strengths were obtained.

The prevalence of COPD increases with age.3 4 5 6 7 One effect of the aging population in the industrialized countries might be an increase in the burden of COPD. This trend indicates that the costs to the society for COPD will become an even greater problem in the future. In the study sample, 47% were smokers and 35% were ex-smokers. Smoking cessation is today the only therapy with an impact on disease progression, and it has also been shown to be cost-effective.42 43 The revenues raised by the Swedish state from sales of tobacco in 1999 amounted to SEK 7.5 billion, less than the estimated societal costs for COPD, which is only one of many tobacco smoking-related diseases. The most important target for primary and secondary prevention of COPD and to save costs is to reduce the use of cigarettes in society.

An important message from our study is that the societal costs caused by COPD are more than twice as large as has been found from register studies,12 the data agreeing well with the substantial underdiagnosis of COPD that has been demonstrated.23 An easy, appropriate and inexpensive way to reduce the underdiagnosis of COPD is the more frequent use of spirometry. Physicians, and the health-care system as well, must make an effort to achieve early detection and diagnosis of COPD aimed at promoting secondary prevention, mainly by means of smoking cessation, in order to prevent progression of the disease to more severe stages.

This study presents comprehensive data on the social cost of COPD. The data should be highly valid since they reflect a real-life setting. In conclusion, there were large variations in both the level and breakdown of costs for COPD, mainly depending on the severity of the disease. The costs for persons with severe disease were 3 times greater than the costs for persons with moderate disease and > 10 times greater than for those with mild disease. The total costs for COPD in Sweden could be estimated at SEK 9.1 billion (USD 871 million, EUR 982 million), with the direct costs accounting for 42% of the total.


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  		Table 6.. General Linear Model of Total Costs (SEK)*

 

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  		Table 7.. Total Costs*

 

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  		Table 8.. General Linear Model of Direct Costs*

 

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  		Table 9.. Direct Costs*

 

   Appendix 1
TOP
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
 Appendix 1
References
 
Multiple linear regression was applied with direct costs and total costs as dependent variables. With disease severity defining four ordered patient groups requiring effectively six comparisons, this was a straightforward way to simultaneously analyze the dependence of costs on disease severity. The analysis was not used to predict costs per se, but to analyze whether disease severity differs in terms of costs. This was found both for total and direct costs (Tables 6 7 8 9 ). Further, early retirement (important for indirect costs) was significantly related with total costs, while living in small municipalities or towns with long distance to hospitals, and age, were related with direct costs. As loss in FEV1 was included in the models, no significant effect by pack-years was found.


   Acknowledgements
 
The authors thank Christin Prütz and Fredrik Berggren, AstraZeneca R&D Lund, Eva Rönmark of the OLIN studies, and Ann-Christine Jonsson of the OLIN studies, Luleå (for collecting data).


   Footnotes
 
Abbreviations: CI = confidence interval; EUR = euros; OLIN = Obstructive Lung Disease in Northern Sweden; SEK = Swedish crowns; USD = US dollars

Financial support was provided by AstraZeneca R&D, Lund, Sweden, and the Swedish Heart-Lung Foundation.

Received for publication July 12, 2001. Accepted for publication June 26, 2002.


   References
TOP
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
 Appendix 1
 References
 

  1. Buist, AS. (1996) Risk factors for COPD. Eur Respir Rev 6,253-258
  2. Doll, R, Peto, R, Wheatley, K, et al Mortality in relation to smoking: 40 years observations on male British doctors. BMJ 1994;149,1218-1226
  3. Lundbäck B, Lindberg A, Lindström M, et al. Not fifteen but fifty percent of smokers develop COPD? Report from the Obstructive Lung Disease Studies in Northern Sweden. Respir Med 2002 (in press)
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  9. Engström, CP, Persson, LO, Larsson, S, et al Reliability and validity of a Swedish version of the St. George’s Respiratory Questionnaire. Eur Respir J 1998;11,61-66[Abstract/Free Full Text]
  10. Sullivan, SD, Ramsye, SD, Lee, TA. The economic burden of COPD. Chest 2000;117,5S-9Ss[Abstract/Free Full Text]
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