All patients fulfilling the GOLD criteria for stage IV disease based on spirometry findings, respiratory insufficiency, or cor pulmonale were informed about the study. None declined inclusion. The Regional Ethics Committee at Umeå University approved the study.
Descriptive statistics are presented as the mean (SD), unless otherwise stated.
A total of 76 patients fulfilled the GOLD criteria for COPD stage IV disease. Of these, 70 patients fulfilled the criteria based on spirometry and/or respiratory insufficiency (
Table 1 ). The remaining six patients fulfilled the criteria based on signs of cor pulmonale only (
Table 2 ). All six patients had an FEV1 of > 30% predicted and no evidence of respiratory insufficiency. They were included in the estimation of prevalence but not in the subsequent description. Thus, the estimated prevalence of physician-diagnosed stage IV COPD in Östersund as of December 31, 2004, was 0.13%, and was 0.26% among individuals in the population who were > 40 years of age.
Forty-five patients lived independently at home. Of these patients, 14 lived alone. Fifteen patients lived at home with community assistance or medical home care, and of these patients, 12 lived alone. The remaining 10 patients were institutionalized. Sixty-five patients were retired due either to age or disease. None of the remaining patients worked > 50% part time.
Sixty-two patients were ex-smokers, 6 patients were present smokers, and 2 patients had never smoked. Forty-seven patients had received a vaccination against influenza within the last year, and 24 patients were vaccinated against Streptococcus pneumoniae within past 5 years. The use of medications is presented in
Table 3 . The most common comorbidity was hypertension (16 patients). Nine patients had diabetes and left ventricular heart failure, eight patients had angina, and six patients had atrial fibrillation. In addition to their COPD, seven patients had asthma and three patients had α1-anti- trypsin deficiency.
The group had a mean Charlson comorbidity index of 1.68 COPD-related hospital contacts (SD, 0.81 COPD-related hospital contacts) with physicians at the Departments of Internal Medicine or Respiratory Medicine, which are presented in
Table 4 . The patients had a mean of 1.3 hospitalizations (SD, 2.3 hospitalizations), 0.4 emergency department visits (SD, 1.5 emergency department visits), and 0.7 elective outpatient visits (SD, 0.8 elective outpatient visits) during 2004. The mean stay for each COPD-related hospitalization was 8.6 days (SD, 9.3 days).
To the best of our knowledge, this is the first study that estimates the prevalence of physician-diagnosed stage IV COPD using the GOLD criteria. This approximation is possible due to an ongoing local integrated care pathway, in which patients in whom severe COPD had been diagnosed are under surveillance by the regional Respiratory Department. Within the present study design, the local prevalence of stage IV COPD was estimated to be 0.13% in the whole population of Östersund, and 0.26% in the population of individuals who were > 40 years of age. This result should not be regarded as an indication of the true prevalence, as the reported prevalence is likely to be an underestimation. The perfect point-prevalence study of physician-diagnosed stage IV COPD would require the simultaneous screening of all patients with COPD in a community, a task that is practically impossible.
The estimated prevalence of physician-diagnosed stage IV COPD in the present study appears to be in accordance with rates of stage IV COPD from epidemiologic studies using spirometry and questionnaires. In those studies, prevalence rates of 0.1% in adults ≥ 40 years of age have been reported from northern Sweden
8 and Japan,
13 and of 0.1% and 0.2% in subjects ≥ 18 years of age in Korea vs Denmark.
14 It is possible that the prevalence of stage IV disease in the present study may have been underestimated, as only 50 to 90% of patients with an FEV1 of < 40% predicted have been shown to have a physician-diagnosed obstructive lung disease in Sweden.
18 Furthermore, the prevalence of physician-diagnosed COPD was based on a selected cohort of patients in whom COPD had been diagnosed at Östersund Hospital. On the other hand, previous epidemiologic studies have included subjects with asthma and have not included patients based on the presence of respiratory insufficiency or cor pulmonale. In all of the studies, the prevalence of COPD is strongly age-related. In contrast, 59% of the patients in the present study were women, compared to 0% and 21% in the Korean and Danish studies.
A total of 326 living patients were identified and were eligible for inclusion in the study. Of these, 76 patients (21%) had stage IV disease, which is a substantial but not unexpected proportion. Six of these patients fulfilled the stage IV criteria based only on clinical signs of cor pulmonale. These patients are presented separately, as these clinical signs have an unknown validity and probably significant interphysician variability. Furthermore, the patients had significant comorbidity that may have affected the signs of cor pulmonale. To include COPD patients based on these criteria would thus be a potential confounding factor in future studies.
To the best of our knowledge, this is the first study with detailed characteristics of patients with physician-diagnosed stage IV COPD. Two previous epidemiologic studies
8 have presented some description of subjects with severe COPD. Lindberg et al
8 found that 8% of a random sample of 1,237 subjects living in northern Sweden had an FEV1 of < 40% predicted. All of these patients had respiratory symptoms, used airway medications, and were smokers or ex-smokers.
8 In the other study, Vestbo and Lange
6 presented information on 33 Danish patients with stage IV disease. They had a mean age of 62 years and a mean FEV1 of 23% predicted, and 61% were current smokers.
6 In contrast, only 9% were current smokers in the present study, whereas 89% were ex-smokers. Moreover, with a mean body mass index of 23, stage IV COPD patients in Östersund were generally not undernourished. An additional positive finding was that 65% of patients lived at home without any community or health-care assistance.
The patients used several daily medications. Unexpectedly, inhaled anticholinergic agents were the most common. Inhaled corticosteroids, alone or in combination, are recommended for treatment in patients with stage III-IV disease and frequent exacerbations.
22 In the present study, 75% of the patients used this medication. Patients with stage IV disease have several risk factors for osteoporosis. Despite this, only 53% of the patients used either biphosphonates or calcium supplementation. Only 34% of the patients had received the vaccine against S pneumoniae, whereas 60% had been vaccinated against influenza. These numbers could probably be increased, but we all know that many patients avoid vaccination and medication out of fear of the side effects.
Comorbidity can predict mortality in patients with COPD,
24 and the Charlson comorbidity index is one of the most extensively used scoring systems.
26 Antonelli Incalzi et al
23 found a comorbidity index of 1.38, and Almagro et al
24 found an index of 2.22 in patients who had been admitted to the hospital for an exacerbation of COPD, compared to 1.68 in the present study. The patients in these studies had slightly higher FEV1 and Po2 values than did the patients in the present study.
Our clinical experience is that patients with severe COPD have frequent contacts with health care. Rennard et al
27 found that 14% of COPD patients in general required emergency care and that 13% were hospitalized yearly. It has also been shown
28 that the severity of COPD is correlated to exacerbations causing hospitalization. In the present study, 11% of the patients required one or more COPD-related emergency visits and 48% required at least one COPD-related hospitalization during 2004. Our data indicate that patients with very severe COPD require periods of hospitalization more often than intermittent emergency visits, compared to COPD patients in general. It is our clinical experience that patients with severe COPD presenting to the emergency department with an exacerbation are usually hospitalized rather than treated as outpatients. It is difficult to know whether the present results indicate high or low health-care consumption by patients with very severe COPD as, to the best of our knowledge, there have been no corresponding studies published. It is therefore also difficult to know whether the present results are regional findings that may not be applicable elsewhere.
The present study indicated that 0.13% of the population in Östersund, Sweden