Abstract
Rationale: Chronic obstructive pulmonary disease (COPD), a common manageable condition, is a leading cause of death. A better understanding of its impact on health-care systems would inform strategies to reduce its burden.
Objectives: To quantify health services use in a large, North American COPD population.
Methods: We conducted a cohort study using health administrative data from Ontario, a province with a population of 13 million and universal health-care insurance. All individuals with physician-diagnosed COPD in 2008 were identified and followed for 3 years. Proportions of all hospital visits, emergency department visits, ambulatory care visits, long-term care residence places, and homecare made or used by people with COPD were determined and rates of each compared between people with and without COPD.
Measurements and Main Results: A total of 853,438 individuals with COPD (11.8% of the population aged 35 yr and older) were responsible for 24% of hospitalizations, 24% of emergency department visits, and 21% of ambulatory care visits; filled 35% of long-term care places; and used 30% of homecare services. After adjusting for several factors, people with COPD had rates of hospital, emergency department, and ambulatory care visits that were, respectively, 63%, 85%, and 48% higher than the rest of the population. Their rates of long-term care and homecare use were 56 and 59% higher, respectively.
Conclusions: Individuals with COPD use large and disproportionate amounts of health services. Strategies that target this group are needed to improve their health and minimize their need for health services.
People with chronic obstructive pulmonary disease (COPD) use significant amounts of health services—often acutely—which impact their lives and place significant burden on health-care systems. In the United States, COPD is responsible for about 1 million hospitalizations and 27 million physician office visits each year, costing 21 to 25 billion dollars annually, and its burden is increasing.
This real-world study quantifies the impact of COPD and its comorbidity on various types of health services and reveals its overall burden on individuals and the health-care system. This knowledge should help health-care providers anticipate the needs of their own patients with COPD and plan accordingly, provide decision makers with a complete description of COPD burden on which to base health-care planning, and educate the general population about the societal impact of this highly prevalent but often underrecognized disease.
Chronic obstructive pulmonary disease (COPD) is a preventable and manageable condition that affects 8 to 22% of adults aged 40 years and older and is a leading cause of death worldwide (1–3). People with COPD use significant amounts of health services—often acutely—which impact their lives and place significant burden on health-care systems. In the United States, COPD is responsible for about 1 million hospitalizations and 27 million physician office visits each year, costing 21 to 25 billion dollars annually, and its burden is increasing (4–6). Despite its significant impact, however, to the best of our knowledge, there has been no study quantifying how often people with COPD use health services. Furthermore, people with COPD have many related comorbidities, such as cardiac disease and lung cancer, and no one has quantified how often they use health services for them (7). Such knowledge would help health-care providers anticipate the needs of their own patients with COPD and plan accordingly, provide decision makers with a complete description of COPD burden on which to base health-care planning, and educate the general population about the societal impact of this highly prevalent but often underrecognized disease (8, 9).
Health administrative data provide a practical way of capturing health services use, which is particularly helpful when it comes from universal, single-payer health-care insurance that captures all encounters from a complete real-world population with minimal bias due to financial barriers to care. Therefore, we conducted a population-based study using health administrative data from Ontario, Canada to quantify the overall proportions and rates of hospitalizations, emergency department visits, ambulatory care visits, long-term care, and homecare used by individuals with COPD and, to contextualize the amounts, compared them with the rest of the population. We also examined how much health services use by individuals with COPD was specifically for COPD and how much was for its attributable comorbidity.
Although knowledge gained using Ontario health administrative data has often been generalized to other jurisdictions (10–12), it is likely to provide a conservative underestimate of health services use by people with limited or no health-care insurance, such as some living in the United States. For financial reasons, these people would be more likely to delay or not seek medical attention and less likely to receive preventive care and, as a result, have more progressive, unstable disease and costly emergency department visits and hospitalizations. Such patients would also be more likely to die, which, although relieving burden from the health-care system, would place greater burden on society. Some of the results of this study have been previously reported in the form of an abstract (13).
We conducted a longitudinal population cohort study using universal health administrative data from Ontario, a province of Canada with a diverse multicultural population of approximately 13 million.
Residents of Ontario have universal public health insurance under the Ontario Health Insurance Plan (OHIP), the single payer for all medically necessary services across the full spectrum of residents, providers, and hospitals. Service details are captured in health administrative databases, which can be linked on an individual level to provide a complete health services profile for each resident. Six Ontario population health administrative databases were used: the Registered Persons Database, containing basic demographic information and date of death; the Canadian Institute of Health Information (CIHI) Discharge Abstract (DAD) and National Ambulatory Care Reporting System (NACRS) databases, containing information on all discharges from acute-care hospitals, same-day surgical procedures, and emergency department visits; the OHIP Physician Claims database containing information about all services provided by fee-for-service physicians and “shadow-billings” for physicians paid under alternate payment plans; the Ontario Home Care database, containing information on all services provided by provincial community care centers in the home; and the Ontario Drug Benefits database, containing information on prescription medications, which are only provided to those aged 65 years or older and those who are on welfare.
All individuals aged 35 years and older living in Ontario on April 1, 2008 were included and followed for 3 years. Those who died or left the province were censored when those events occurred.
Physician-diagnosed COPD was the main exposure. Individuals were identified as having physician-diagnosed COPD if they met a previously validated case definition based on health administrative data consisting of being aged 35 years and older and having one COPD hospitalization and/or one COPD ambulatory care claim. This case definition had a sensitivity of 85.0% and a specificity of 78.4% when compared with real-world clinical evaluation by a physician (which may or may not have included spirometry). More details of it and examples of its use can be found elsewhere (11, 14, 15).
The primary outcomes were rates of all-cause hospitalizations, emergency department visits, ambulatory care visits, homecare use, and long-term care residence as ascertained from claims in the health administrative data. A person was determined to be residing in a long-term care facility if they had an OHIP or Ontario Drug Benefits claim code that specified they lived there. Because it was possible for multiple ambulatory care claims to occur during one day, only one ambulatory care claim per physician per patient per service day was used to avoid overcounting health service use. Health services use for all causes, instead of just for COPD, were considered so as to not miss use for COPD comorbidities. COPD-specific hospitalization, emergency department visit, and ambulatory care visit rates were secondary outcomes.
Because characteristics of people with and without COPD generally differ from the general population, multivariable analysis was used to adjust for potential confounding demographic and clinical variables when comparing health services use. Socioeconomic status was inferred from neighborhood income derived from postal codes and census data (16). Rural status was based on Statistics Canada’s definition of rurality (17). Because it could potentially be misclassified as COPD, a codiagnosis of asthma, also derived from health administrative data, was considered (18).
Continuous and categorical characteristics were compared by t tests and chi-square tests, respectively, between individuals with and without COPD. Proportions of all the hospitalizations, emergency department visits, and ambulatory care visits in Ontario made by people with COPD and the proportions of all individuals in Ontario living in long-term care and using homecare who had COPD were determined.
Rates of all-cause health services use were calculated for individuals with and without COPD. Rates for hospitalizations, emergency department visits, and ambulatory care visits were per 1,000 person-years, and rates for long-term care and homecare use were per 1,000 individuals. Ninety-five percent confidence intervals were calculated using the γ distribution (19).
In each health-care domain, the adjusted relative rate of health services use for those with COPD compared with the rest of the population adjusting for all potential confounders was estimated using a general linear model. All analyses were done using SAS 9.1 software (Cary, NC).
To determine if rates of health services use differed between those who had been newly diagnosed and those with existing disease, we stratified our crude rates by incident and prevalent COPD. To characterize the role of asthma in our cohort, we stratified our crude rates by those who had only COPD, asthma and COPD, and neither asthma nor COPD. We also added rates of health services use in those with only asthma for comparison.
To determine what health services used by people with COPD were being used for—COPD or its comorbidity—further analyses were conducted. Borrowing methods used in previous studies (20), COPD-attributable comorbidity, or the additional amount of comorbidity found in individuals with COPD, was estimated by subtracting rates of COPD-specific hospitalizations or visits from differences in corresponding all-cause rates between individuals with and without COPD. Thus, all additional, non-COPD–specific claims in the COPD group were considered COPD-attributable comorbidity regardless of cause. We considered claims with all diagnoses to capture the numerous comorbidities that have been associated with COPD.
To determine if differences in age between individuals with COPD and the rest of the population were driving our results, we stratified by younger (35–64 yr) and older (65 yr and older) adults. To determine if hospitalization, emergency department visit, and ambulatory care visit rates were being driven by a few high users of these services, we calculate rates of these services per 1,000 individuals instead of per 1,000 person-years.
To assess if it was plausible that misclassification of COPD due to less than perfect specificity of the case definition was responsible for the observed results, an array approach was used (21). The inclusion of misclassified people could have potentially led to incorrect results if the misclassified people were healthier (or less healthy) than those correctly identified. Therefore, we estimated the corresponding relative risks when different assumptions about the health of those who were misclassified relative to those who truly had COPD were made. We were specifically interested in what assumptions caused the adjusted relative risks of health services use to be reduced to 1.0 (or no increased risk).
Research ethics approval was obtained from the institutional review board at Sunnybrook Health Sciences Centre, Toronto, Ontario.
There were 7,246,982 residents of Ontario aged 35 years and older on April 1, 2008, of whom 731,717 were identified as having physician-diagnosed COPD. Because COPD is a disease with a slow, insidious onset, the 121,721 individuals diagnosed with COPD during the follow-up period were also presumed to have COPD, for a total of 853,438 (11.8%) individuals in the physician-diagnosed COPD cohort (Figure 1). Individuals with COPD were older and more likely to be men, of low socioeconomic status, live in a rural area, and have asthma (Table 1).
Figure 1. Flowchart of study subjects. COPD = chronic obstructive pulmonary disease.
[More] [Minimize]| Characteristic | COPD Population | Non-COPD Population | P Value |
| N (%) | 853,438 (11.8) | 6,393,544 (88.2) | |
| Age, mean ± SD, yr | 64.7 ± 13.8 | 53.5 ± 13.3 | <0.001 |
| Female, % | 50.6 | 52.2 | <0.001 |
| Socioeconomic status,% | <0.001 | ||
| Quintile 1 (lowest) | 23.4 | 18.1 | |
| Quintile 2 | 21.8 | 19.4 | |
| Quintile 3 | 16.4 | 19.9 | |
| Quintile 4 | 18.4 | 21.0 | |
| Quintile 5 (highest) | 16.7 | 21.4 | |
| Rural (vs. urban), % | 16.2 | 11.9 | <0.001 |
| Asthma, % | 29.4 | 8.9 | <0.001 |
| Deaths, % | 5.2 | 1.1 | <0.001 |
About one-fifth to one-third of all health services used in the province were used by individuals with COPD (Figure 2).
Figure 2. Proportion of all hospitalizations, emergency department visits, ambulatory care visits, long-term care residence places, and homecare made or used by individuals with chronic obstructive pulmonary disease (COPD).
[More] [Minimize]Compared with the rest of the population, individuals with COPD had significantly higher crude rates of all types of health services use examined (Table 2). Corresponding adjusted relative rates of health services use ranged from 1.48 for ambulatory care visits to 1.85 for emergency department visits (Figure 3).
| Crude Rate* of Health Services Use (SE†) | |||
| Type of Health Services Use | COPD Population | Non-COPD Population | Absolute Difference* |
| Hospitalizations | 503 (0.45) | 203 (0.10) | 300 |
| Emergency department visits | 802 (0.57) | 328 (0.13) | 474 |
| Ambulatory care visits | 20,128 (2.86) | 9,831 (0.72) | 10,297 |
| Long-term care residence | 82 (0.31) | 20 (0.06) | 62 |
| Homecare visits | 270 (0.56) | 86 (0.12) | 184 |
Figure 3. Relative rates of health services use in individuals with chronic obstructive pulmonary disease compared with the rest of the population adjusted for age, sex, socioeconomic status, rural/urban residences, and a codiagnosis of asthma.
[More] [Minimize]When crude rates of hospitalizations, emergency department visits, and ambulatory care visits were measured per 1,000 individuals instead of per 1,000 person-years, absolute differences were smaller (but still notable) for hospitalizations and emergency department visits, suggesting that individuals with repeat health services use were responsible for some of the increased burden. The absolute difference was much smaller for ambulatory care visits, as almost everyone in both cohorts saw a physician at least once (see Table E1 in the online supplement).
Relatively small proportions of the additional hospitalizations, emergency department visits, and ambulatory care visits in individuals with COPD were specifically for COPD. Most were used for COPD-attributable comorbidity (Table 3).
| Crude Rate of Health Services Use per 1,000 Person-Years (SE*) | |||
| Type of Health Services Use | Type of Claims | COPD Population | Non-COPD Population |
| Hospitalizations | All-cause | 503 (0.45) | 203 (0.10) |
| COPD-specific | 43 (0.13) | na | |
| COPD-attributable comorbidity† | 257 | na | |
| Emergency department visits | All-cause | 802 (0.57) | 328 (0.13) |
| COPD-specific | 55 (0.15) | na | |
| COPD-attributable comorbidity† | 420 | ||
| Ambulatory care visits | All-cause | 20,128 (2.86) | 9831 (0.72) |
| COPD-specific | 627 (0.51) | na | |
| COPD-attributable comorbidity† | 9670 | na | |
Individuals with incident COPD used more health services than those with prevalent COPD (Tables E2 and E3).
Individuals who had both COPD and asthma used more health services than those with COPD only (Tables E4 and E5).
Fifty-eight percent of individuals with COPD were between 35 and 64 years, and the rest were 65 years and older. Differences in characteristics of individuals with and without COPD in these two age groups differed little from the overall group (data not shown). Compared with those aged 35 to 64 years, individuals aged 65 years and older used more health services, had bigger absolute differences in health services use between those with and without COPD (Tables E5 and E6), and had smaller (but still notable) adjusted relative rates of health services use (Figures E1 and E2).
In the unlikely scenario that individuals who were potentially misclassified as having COPD had more than twice the health services use as those with true COPD, misclassification could have accounted for the results seen. In the more likely scenario that individuals who were potentially misclassified with COPD had less health services use than those with true COPD (ie. because they truly had asthma), the relative risk of health services use would be much greater than that observed.
We conducted a longitudinal population study using health administrative data and found that individuals with physician-diagnosed COPD, who composed 11.8% of the population, were responsible for up to one-third of all hospitalizations, emergency department visits, ambulatory care visits, long-term care resident places, and homecare use in the province of Ontario, Canada. To account for this, we found that people with COPD had 63% higher rates of hospitalizations, 85% higher rates of emergency department visits, and 48% higher rates of ambulatory care visits than the rest of the population. Their rates of long-term care and homecare use were also, respectively, 56 and 59% higher. Finally, we found that most of the additional health services used by individuals with COPD were for COPD-attributable comorbidity—suggesting that it accounts for a large, and previously unappreciated, COPD disease burden. To the best of our knowledge, this is the first large, real-world study to quantify the complete impact of this relatively neglected disease and its comorbidity on various types of health services and reveal its overall burden on individuals and the health-care system (8, 9). This knowledge will help health-care providers better understand and care for their patients and help decision makers with health-care planning. It can also be used to educate the general population about the societal impact and need for resources to address COPD (8, 9).
Our findings are consistent with previous studies demonstrating the large burden that COPD places on health-care systems and society (2, 11, 15). They are also consistent with studies demonstrating greater levels of various types of comorbidity in individuals with compared with those without COPD (22–24). Finally, they agree with previous studies demonstrating a much higher rate of all-cause hospitalizations compared with COPD-specific hospitalizations in people with COPD (25). Our study extends these previous findings by quantifying and contextualizing the impact of COPD, including that due to COPD-attributable comorbidity, on several types of different health services in a large, complete real-world population. By doing so, it reveals a more representative burden of COPD on individuals and society.
Our study demonstrated that people with COPD were more likely to use health services, which is not always undesirable. If use of ambulatory care and homecare prevents acute hospitalizations and emergency department visits, as has been shown to occur with COPD, then it should be encouraged (26).
The strengths of our study were its population base, comprehensiveness, and ability to capture and compare virtually all health services use in individuals with COPD to the rest of the population with minimal bias due to financial barriers to care. It also has limitations that merit emphasis. First, even though our health administrative case definition has been validated, some individuals with physician-diagnosed COPD may have been misclassified as non-COPD and vice versa. Overall, however, because COPD is underdiagnosed by physicians and because physician diagnosis is less sensitive than spirometry for identification of true COPD, we believe our absolute measures of COPD burden likely underestimate true COPD burden (3, 27). In addition, because our relative measures of health services use were based on differences between individuals with and without COPD, misclassification would have caused them to also be underestimates. To address this further, we conducted a sensitivity analysis, which showed that only in the extremely unlikely scenario wherein all those misclassified with COPD had more than twice the amount of health services use as those with true COPD would the increased relative risks of health services use associated with COPD be negated. In many cases, the people misclassified as having COPD most likely had other diseases that are often mistaken for COPD, such as asthma—which is not associated with such high health services use.
A second important limitation, as mentioned above, is the generalizability of the results. Although studying a population with universal health-care coverage may minimize bias due to financial barriers, it might underestimate the burden of COPD in jurisdictions without universal coverage, such as the United States. Uninsured patients are less likely to use ambulatory care services and homecare and are more likely to require costly acute health services and die. Because of this likelihood of underestimating health services use, and because similarities between health care in Canada and other westernized countries greatly outweigh their differences, the high rates of health services use observed should be of concern to health-care providers and decision makers in jurisdictions without universal health-care insurance as well. Another issue is that because identification of disease depends on health service use, people with more health services are more likely to be diagnosed with COPD and other diseases. These are also likely people with moderate to severe disease. Therefore, our study might have missed those with milder disease.
Third, without spirometric results we were not able to stratify and examine health services use by conventional categories of COPD severity (28). However, we were able to stratify by severity as indicated by health services use, with those requiring hospitalization having severe disease, those requiring emergency department visit having moderate disease, and those not requiring any acute services having milder disease. Thus, differences in health services use by COPD severity of disease were examined.
Finally, our study demonstrated an excess of non-COPD claims in individuals with COPD, which we believe is attributable to the significant comorbidity known to occur in this population; however, there might also be other explanations. Therapies for COPD may also cause or contribute to comorbidity. Oral corticosteroids are well known to produce significant adverse effects that demand medical attention, but even inhaled corticosteroids may predispose to osteoporosis, increased fracture risk, and pneumonia (29, 30). Alternatively, some of the increased health services use for COPD may represent diagnostic confusion or lack of precision. Miscoding of asthma may fall into this category. Third, use of health services relies on access, and because individuals with COPD have established some form of access for their treatment they may be more likely to use health-care services than individuals without COPD. In Canada, universal health care ensures that lack of money is not a barrier to access; however, other barriers, such as lack of time and education, may still exist. Finally, using health care may be a learned behavior, and individuals who have consistent contact with their physician because of their COPD may have learned to use, and perhaps overuse, health-care resources, whereas those who have not might be more likely to self-treat. Future studies exploring the reason for increased non-COPD health services use in individuals with COPD would help learn how to best prevent and/or manage it.
In conclusion, COPD—a relatively neglected disease—has a huge impact, both directly and indirectly through its comorbidity, on various health services. Future study should confirm these findings in other countries and in clinical populations.
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Study supporters had no role in study design, collection, analysis, interpretation of data, writing of the report, or in the decision to submit the report for publication. The opinions, results and conclusions reported in this paper are those of the authors and are independent from the funding sources. No endorsement by ICES or the Ontario Ministry of Health and Long-Term Care is intended or should be inferred.
Funded by the Government of Ontario. This study was also supported by the Institute for Clinical Evaluative Sciences (ICES), which is funded by an annual grant from the Ontario Ministry of Health and Long-Term Care. A.S.G. was supported by a Career Scientist Award from the Ontario Ministry of Health and Long-Term Care while working on this study and is currently supported through a New Investigator Award funded by team grant OTG-88591 from the Canadian Institutes of Health Research Institute of Nutrition, Metabolism and Diabetes. T.T. is supported by The Dales Award in Medical Research from the University of Toronto, Toronto, Ontario, Canada.
Author Contributions: A.S.G. participated in the study conception and design; acquisition, analysis, and interpretation of data; drafting and critical revision of the manuscript; obtaining funding; supervising writing; and approving the final version. J.G. participated in the analysis and interpretation of data, statistical analysis and critical revision of the manuscript, and approving the final version. J.C.V. participated in the study conception and design, analysis and interpretation of data, critical revision of the manuscript, and approving the final version. R.G. participated in the study conception and design, analysis and interpretation of data, critical revision of the manuscript, and approving the final version. T.T. participated in the conception and design, analysis and interpretation of data, critical revision of the manuscript, and approving the final version.
This article has an online data supplement, which is accessible from this issue’s table of contents at www.atsjournals.org
Originally Published in Press as DOI: 10.1164/rccm.201211-2044OC on January 17, 2013
Author disclosures
