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Update of prognosis and characteristics of chronic obstructive pulmonary disease in a real-world setting: a 5-year follow-up analysis of a multi-institutional registry

BMC Pulmonary Medicine volume 24, Article number: 556 (2024) Cite this article

Abstract

Background

We conducted a prospective observational study to elucidate the long-term prognosis and management of chronic obstructive pulmonary disease (COPD) in clinical practice in Japan in the mid-2010s.

Methods

This prospective cohort study included 29 facilities. Data from 427 patients clinically diagnosed with COPD, enrolled between September 2013 and April 2016, were analyzed. Interstitial pneumonia was excluded through a central multidisciplinary discussion. Follow-up data were collected for up to 5 years after patient registration.

Results

At the time of registration, 53 patients clinically diagnosed with COPD did not have airflow limitation (AFL). In the cohort with AFL (n = 374), 232 patients completed a 5-year follow-up, while 49 patients died during the 1576.6 person-years of observation. The mean age was 71.7 years with an overall 5-year survival rate of 85.4%. Stratified by % forced expiratory volume in one second (FEV1), survival rates were 93.6% in the mild and moderate AFL group, 82.5% in the severe AFL group, and 66.1% in the very severe AFL group. The prognosis of the subpopulation without AFL was poor with a 5-year survival of 81.6%. This subpopulation exhibited respiratory symptoms, low vital capacity and total lung capacity, and emphysematous changes.

Conclusions

Our study presents the 5-year survival and real-world clinical practice scenario of a prospective cohort of patients clinically diagnosed with COPD in Japan in the mid-2010s. The survival rates of our cohort were numerically better than the Japanese cohort in the 1990s, regardless of the high median age of this cohort. Overall, 12.4% of the patients in this cohort with no AFL at registration exhibited respiratory symptoms and distinct spirometric patterns, and had a poor prognosis.

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Background

Chronic obstructive pulmonary disease (COPD) is the third leading cause of death worldwide, and its incidence is expected to increase [1]. The background characteristics of patients with COPD can evolve over time as a result of shifts in social structures. In particular, aging influences prognosis. The prognosis of COPD has improved with treatment such as long-term oxygen therapy for patients with resting hypoxemia, non-invasive ventilation, and inhaled long-acting muscarinic antagonists (LAMAs), long-acting β2-agonists (LABAs), and corticosteroids (ICSs) for patients with low pulmonary function and frequent exacerbations [2,3,4,5]. Consequently, the prognosis of COPD may change over time, influenced by both changes in patient demographics and advancements in therapeutic strategies. A comparison of two independent cohorts in the 1990s and the mid-2000s revealed that patients with severe COPD in the latter group had a better prognosis [6, 7]. However, there are no data on the prognosis of COPD in real-world settings after 2010 in Japan. Currently, Japan is experiencing the most advanced population aging worldwide, and other countries are predicted to follow soon [8]. Therefore, the Japanese data on COPD prognosis and management can act as a reference for other countries with aging populations, particularly in East Asia.

The diagnosis of COPD requires a forced expiratory volume in one second (FEV1) / forced vital capacity (FVC) < 0.7 post-bronchodilation, signifying airflow limitation (AFL). However, several smokers reportedly experience respiratory symptoms without AFL. Preserved ratio impaired spirometry (PRISm) refers to a decreased FEV1 in patients who do not meet the definition of an obstructive airflow pattern. Patients with PRISm reportedly have a higher mortality than individuals with normal lung function and even mild COPD in community-based observational studies [9,10,11]. While PRISm has an estimated global prevalence of approximately 10% and is gaining recognition, it is often overlooked in real-world practice [12]. These data highlight the importance of focusing on populations that do not meet the COPD criteria. In this group, which includes smokers with no obstructive impairment, interstitial lung abnormalities have been reported in 8–10% of individuals; previous reports may have included patients with interstitial shadows on CT imaging, which are associated with poor prognosis [13, 14].

This study analyzed data from a multi-center prospective cohort to elucidate the prognosis and treatment of COPD in a real-world setting in the mid-2010s. We also investigated the prognosis and clinical characteristics of patients without AFL clinically diagnosed with COPD, excluding those with comorbid interstitial lung disease.

Methods

Study design

This was a prospective and multi-center observational study of patients with COPD and idiopathic interstitial pneumonia (IIP) from 29 centers who were followed up longitudinally for 5 years. The aim of this study was to investigate the current state of tobacco-related lung disease (COPD and IIP) [15].

Study patients

The main inclusion criteria were age > 20 years and diagnosis of COPD or IIP. The diagnosis of COPD was made by clinicians based on the symptoms and clinical data according to international guidelines [16]. However, no exclusion criteria for pulmonary function tests were established at enrolment and the evaluation of airway reversibility was not mandatory. Patients (regardless of whether newly or previously diagnosed) were sequentially enrolled after a diagnosis of COPD or IIP by a respiratory specialist at the participating facilities. The total planned enrolment number was set at 1000 without sample size calculations. A total of 1024 patients were recruited between September 1, 2013, and April 30, 2016. Of these, eight were subsequently excluded on the basis of patient refusal (n = 4), missing test results (n = 2), failure to meet the inclusion criteria (n = 1), or an unknown reason (n = 1). The remaining 1016 patients were enrolled in the study. All diagnoses of the enrolled patients were re-evaluated by a central diagnosis committee comprising pulmonologists, subspecialist radiologists, and histopathologists. Cases with combined pulmonary fibrosis and emphysema and interstitial lung abnormality were classified as IIP [17]. After central diagnosis, 461 patients were diagnosed with COPD and 543 patients were diagnosed with IIP [17]. Follow-up surveillance was conducted annually for 5 years to evaluate exacerbation and death. Exacerbation was defined as an increase in shortness of breath, cough, or sputum production, or the onset or worsening of chest discomfort, requiring changes to treatment during the stable phase, as determined by a clinician and based on international criteria [16]. Patients with worsening dyspnea determined by a clinician to be due to other causes, such as bacterial pneumonia, and not associated with a COPD exacerbation, were excluded. The moderate to severe exacerbations of COPD were defined as events requiring the use of systemic steroids or antibiotics. All examinations and investigations were performed as part of routine care for each patient at the physician’s discretion and no additional visits or investigations were mandated for this study.

Pulmonary function tests and CT

Predicted FEV1 and VC were calculated using a reference equation reported by the Japanese Respiratory Society (JRS) in 2001 [18]. Among participants with AFL the severity of air flow obstruction was defined using the predicted FEV1 value, as follows: mild and moderate, FEV1 ≥ 50% of predicted; severe, 30% ≤ FEV1 < 50% of predicted; very severe, FEV1 < 30% of predicted. The predicted total lung capacity (TLC) and residual volume (RV) were calculated using the JRS prediction formula as standard values. To determine the volume of emphysema, the volume of low-attenuation areas (LAA) on 5-mm collimation computed tomography (CT) scans was calculated with a threshold of −910 Hounsfield units as previously described [19]. Dedicated software programs (3DSlicer; http://www.slicer.org) were used to quantify LAA. Total lung capacity by CT (TLCct) was calculated using inspiratory CT, and TLCct−VC was obtained as a surrogate value for RV; the ratio of TLCct−VC to predicted RV was calculated as %RV.

Informed consent

This prospective, multi-center, observational study was approved by the Institutional Review Board of Kyushu University (#25–135, August 23, 2013; #555-00, August 27, 2013) and by the institutional review boards of all participating hospitals. Written informed consent was obtained from all patients.

Patient and public involvement

Patients or the public were not involved in the design, or conduct, or reporting, or dissemination plans of our research.

Statistical analysis

The cumulative survival rate was estimated using the Kaplan–Meier analysis. Hazard ratios (HR) were estimated using a Cox regression model to evaluate the association between background characteristics and survival. In the analysis of 374 patients with AFL, statistical comparisons between groups were made using the mild and moderate AFL group as the reference group. The clinical characteristics of the 53 patients without AFL were evaluated by statistical comparison with mild and moderate AFL group. A backward stepwise method was adopted with the significance level for removal set at 0.05 to select a model to predict survival. Statistical significance was set at p < 0.05. All statistical analyses were performed using the SAS version 9.4 (SAS Institute, Cary, NC, USA). Explanatory variables that had a long right tail and were suitable for regression on percentage change were logarithmically transformed in the regression analysis.

Results

Study subjects

Between September 2013 and April 2016, 461 patients were diagnosed with COPD by pulmonologists based on clinical data and symptoms and were enrolled in this study. Of these, five with inadequate imaging, nine who underwent lobectomy, and 20 with missing follow-up data after initial enrolment were excluded from the analysis; finally, the data from the remaining 427 patients were analyzed (Fig. 1). The median age of the total population was 72 years, with 87.1% being male, 97.4% having a history of smoking, and 99.5% presenting with more than 5% low attenuation areas (LAAs) on CT imaging. In total, 374 patients (87.6%) in the COPD cohort showed AFL (defined as FEV1/FVC < 70%), while 53 (12.4%) had no AFL. The 374 patients with AFL were categorized into three groups according to %FEV1. The numbers of patients with mild and moderate AFL, severe AFL, and very severe AFL were 197, 112, and 65, respectively (Table 1).

Fig. 1
figure 1

Flow diagram for the study. COPD, chronic obstructive pulmonary disease

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Table 1 Baseline characteristics of participants, according to pulmonary function categories at registration
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Characteristics of the FEV1/FVC < 70% population

Among the 374 patients with AFL, the most common comorbidity was hypertension, which accounted for 40.4% of all patients. Past history of bronchial asthma accounted for 17.4% of patients with AFL and was more frequent in the severe AFL group. Dyspnea, assessed using the modified Medical Research Council (mMRC) score, was significantly higher in patients with severe and very severe AFL (Table 1). Sputum and weight loss were more frequent in the very severe AFL group, and body mass index was also lower in the very severe AFL group (Table 2). The %VC at registration was preserved in the mild and moderate AFL and severe AFL groups, while it decreased in the very severe AFL group. Additionally, RV/TLC, %RV, and LAA increased with increasing severity of AFL (Table 3). Blood test results showed no significant differences between the groups except for the white blood cell count (Table S1).

Table 2 Baseline symptom and performance status according to pulmonary function categories at registration
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Table 3 Baseline CT and pulmonary function test of participants, according to pulmonary function categories at registration
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Regarding treatment, 86.3% of patients in the mild and moderate AFL group, 96.4% in the severe AFL group, and 98.5% in the very severe AFL group used inhaled drugs. The most commonly used medication were LAMAs. ICSs were used by 37.5% patients in the mild and moderate AFL group, 66.9% patients in the severe AFL group, and 76.9% patients in the very severe AFL group. Home oxygen therapy was used in 58.5% of the very severe AFL. Phosphodiesterase inhibitors are not approved for use in Japan and their usage was not recorded (Table 4).

Table 4 Baseline treatment of participants, according to pulmonary function categories at registration
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5-year survival and exacerbation among the FEV1/FVC < 70% population

Among 374 patients with AFL, 232 completed the 5-year follow-up while 49 died during the 1576.6 person-year observation period (Figure S1). The 5-year survival rate of all patients with AFL was 85.4% and specifically, 93.6% in the mild and moderate AFL group, 82.5% in the severe AFL group, and 66.1% in the very severe AFL group (Fig. 2). The HR for mortality adjusted for age, sex, body mass index (BMI), and smoking (pack-year) was 2.43 (95%CI: 1.10–5.37) in the severe AFL group and 7.73 (95%CI: 3.51–17.02) in the very severe AFL group considering the mild and moderate AFL group as a reference (Table S2). The prognosis of the AFL group was evaluated based on the ADO index, which is a simple and validated prognostic assessment established in 2009 [20]. The point estimates for 3-year survival were better than the original report, with 100% for those with an ADO score of 0–2 points, 98.2% for those with 3–4 points, 89.3% for those with 5–6 points, and 63.6% for those with 7–10 points (Figure S2 and Table S3). The most common cause of death was respiratory disease other than lung cancer, accounting for 46.9% of all deaths, with the frequency increasing in the groups with lower %FEV1. Deaths associated with lung and non-lung cancer malignancies each accounted for 8.2% of all deaths. In contrast, cardiovascular death occurred in only two cases (Table 5). A total of 283 events were moderate to severe exacerbations. The percentages of patients with at least one moderate to severe exacerbation and more than two exacerbations in five years were as follows: 8.6% and 4.0% in the mild and moderate AFL group, 30.4% and 11.6% in the severe AFL group, and 63.1% and 35.4% in the very severe AFL group, respectively (Table S4).

Fig. 2
figure 2

Kaplan–Meier plots of survival probability according to baseline lung function categories. FVC, forced vital capacity; FEV1, forced expiratory volume in one second

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Table 5 Cause of death of participants, according to pulmonary function categories at registration
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Prognostic factors for mortality of FEV1/FVC < 70% population

The predictors of mortality in patients with FEV1/FVC < 70% were examined using a simple Cox regression analysis of baseline factors (Table S5). In multivariate Cox regression analysis (stepwise variable selection), age, number of comorbidities, performance status, weight loss, C-reactive protein level, and % RV were independently associated with mortality (Table S6).

Characteristics of patients without airflow limitation

In the present cohort, 53 patients (12.4%) had a FEV1/FVC ≥ 70% at the time of enrolment. This population was also analyzed retrospectively for mortality and clinical characteristics. The 5-year survival rate in this population was 81.6%, which was significantly lower than that of the mild and moderate AFL group (adjusted HR of 2.94 with a 95% CI of 1.16–7.42) and similar to that of the severe AFL group (Fig. 2 and Table S2).

No differences in age, sex, smoking prevalence, and respiratory symptoms were found between patients with an FEV1/FVC ≥ 70% and the mild and moderate AFL group. The group with FEV1/FVC ≥ 70% had a lower VC and TLC, and certain area of LAAs. Treatment in the group with FEV1/FVC ≥ 70% was similar to that of the mild and moderate AFL group, with 84.9% of patients using an inhaler at registration (Tables 1, 2, 3 and 4). In the group with FEV1/FVC ≥ 70%, 43.5% showed obstructive impairment after one year. Conversely, 17 out of 339 patients (5.0%) in the AFL group had an FEV1/FVC ≥ 70% (Table S7).

Discussion

We conducted a 5-year survival analysis of a cohort of patients with a clinical diagnosis of COPD. Our study demonstrated that, despite the progressively aging population in Japan, the prognosis of patients with COPD has improved over time. Moreover, 12.4% of the patients clinically diagnosed with COPD had no AFL, and their prognosis was poorer than that of patients with mild and moderate AFL.

This prospective study included 374 patients with AFL at registration and elucidated the management of COPD in clinical practice and its prognosis in Japan in the mid-2010s. Our cohort exhibited a high prevalence of male patients and low BMI, consistent with previous Japanese reports [21,22,23]. Life expectancy in Japan increased from 79.6 to 83.9 years in the 20 years between 1995 and 2015, as observed in other countries [8]. Thus, the mean age of our cohort was 71.7 years, with approximately 20% being over 80 years of age, representing the real-world scenario in Japan, which is characterized by a super-aging society. In the 1990s, a prospective study in Japan with a mean age of 68.7 years reported 5-year survival rates of approximately 90% for patients with 50 ≤ %FEV1, 80% for patients with 30 ≤ %FEV1 < 50, and 60% for patients with %FEV1 < 30 [24]. The 5-year survival rates of the severe AFL group (82.5%) and very severe AFL groups (66.1%) in our cohort were numerically better than the Japanese cohort in the 1990s, regardless of the high median age, and the survival rates evaluated using the ADO score were also favorable. The improved prognosis of this cohort may be attributed to advancements in treatment and healthcare. In our study, 90.9% of patients AFL used an inhaler and 53.2% of patients with AFL used ICS. The high prevalence of ICS use may be attributed to the recommendations set out in the 2013 guidelines for patients with COPD. These guidelines recommend the concurrent use of ICS in patients with %FEV1 below 50 or those experiencing frequent exacerbations [16]. Furthermore, this cohort included patients with a history of bronchial asthma. Nonetheless, the exacerbation rate was low in our cohort. Lower exacerbation rates have been reported in the Japanese population, suggesting potential ethnic differences in exacerbation frequencies [25]. The most common causes of death were respiratory disease, followed by lung cancer and other malignancies, which is consistent with to previous reports in Japan [26]. Notably, there were only two cases of cardiovascular death. In western countries, cardiovascular deaths are reported to account for 20–30% of total deaths [27], while in Japan, cardiovascular deaths have been reported to be as low as 11% [26]. Racial differences may contribute to the lower incidence of exacerbations and cardiovascular deaths in this cohort.

In this cohort, 12.4% patients did not have AFL but were treated as having COPD and had a poor prognosis. In addition to respiratory-related deaths, cancer-related deaths were also frequently observed. The majority of this population had a history of heavy smoking, 35.7% had dyspnea on exertion with an mMRC ≥ 2, and 52.8% had a wet cough. On examination, VC and TLCct were low and FEV1 was preserved with a certain extent of emphysema. At the time of registration, 86.8% of this population underwent respiratory treatment. In the SPIROMICS and COPDGene studies, two large longitudinal observational studies, 23–50% of current and former smokers with normal spirometry had respiratory symptoms, and 20–42% underwent treatment interventions [28, 29]. Similarly, a meta-analysis showed that approximately one-fourth of patients treated for COPD in primary healthcare settings did not show obstructive impairment on spirometry [30]. Consistent with these studies, our study highlights the presence of a population with respiratory symptoms that clinicians treat as COPD, even without AFL, in the real-world setting. Patient with PRISm reportedly have a higher mortality than those with normal lung function and even mild COPD in community-based observational studies [9,10,11]. However, these studies did not exclude interstitial pneumonia. It has been reported that approximately 8–10% of smokers exhibit interstitial lung abnormalities, with a higher prevalence observed particularly in cases without airflow limitation [13, 14]. A unique aspect of this cohort is that we demonstrated poor prognosis in cases clinically diagnosed with COPD after excluding interstitial pneumonia. Respiratory symptoms and the extent of emphysema are associated with poor prognosis, even in smokers without AFL [31,32,33,34]. Populations with restrictive spirometric patterns have higher mortality rates [31, 35, 36]. Therefore, the poor prognosis in the FEV1/FVC ≥ 70% group may be attributed to the considerable rate of respiratory symptoms, imaging abnormalities, and low VC, all of which are reportedly associated with mortality. Therefore, our study suggests the importance of multidimensional evaluation of patients with respiratory symptoms, including pulmonary function tests and imaging.

Some longitudinal observational studies have reported that approximately 10% of patients with obstructive patterns in pulmonary function tests become free of obstructive patterns after annual follow-up [9,10,11]. Therefore, it is possible that some patients in the FEV1/FVC ≥ 70% group in this cohort met the definition of COPD at the time of diagnosis. Interestingly, in the one-year follow-up of lung function, 43.5% of patients in the FEV1/FVC ≥ 70% group exhibited obstructive impairment, while 17 out of 339 cases (5.0%) in the AFL group had an FEV1/FVC ≥ 70%. Although it has been reported that lung function can change over long-term observation, the significant variability observed in a short period of time is instructive. Further investigation is needed to determine whether individuals with phenotypes characterized by fluctuations in lung function have a poor prognosis [9, 10, 37].

The following limitations of this study should be acknowledged: some of the enrolled patients were not newly diagnosed with COPD, lung function was not confirmed at the time of diagnosis, and the time of diagnosis was not recorded. Airway reversibility assessment, six-minute walk tests and DLCO measurements were optional, and as a result, indices such as the BODE index could not be calculated. Additionally, the health-related quality of life and physical activity were not assessed. Moreover, only patients who provided informed consent, and not consecutive patients, were enrolled. Finally, despite the execution of annual protocolized assessments, some data were missing.

Conclusions

This study presents the 5-year survival and real-world clinical practice data of a prospective cohort of patients clinically diagnosed with COPD in Japan in the mid-2010s. The high survival rates in our cohort were numerically better than the Japanese cohort in the 1990s, regardless of the high median age of the participants. Overall, 12.4% of the patients in this cohort did not show AFL at registration and exhibited respiratory symptoms and distinct spirometric patterns, and had a poor prognosis.

Data availability

The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.

Abbreviations

COPD:

Chronic obstructive pulmonary disease

MDD:

Multidisciplinary discussion

FEV1:

Forced expiratory volume 1 s

FVC:

Forced vital capacity

AFL:

Airflow limitation

PRISm:

Preserved ratio impaired spirometry

IIPs:

Idiopathic interstitial pneumonias

JRS:

Japanese Respiratory Society

TLC:

Total lung capacity

RV:

Residual volume

LAA:

Low attenuation areas

CT:

Computed tomography

TLCct:

Total lung capacity by CT

HR:

Hazard ratio

mMRC:

Modified Medical Research Council

LAMA:

Long-acting muscarinic antagonist

ICS:

Inhaled corticosteroids

HOT:

Home oxygen therapy

PS:

Performance status

BMI:

Body mass index

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Acknowledgements

The authors thank the patients, their families, and all the investigators participating in the Fukuoka Tobacco-Related Lung Disease (FOLD) registry group. The authors would like to thank the Clinical Research Support Center of Kyushu for their official work on the study.

Funding

This study was supported by a grant from the Ministry of Education, Culture, Sports, Science and Technology: the broad-area, network-based project to drive clinical research at Kyushu University Hospital, a grant from by Boehringer Ingelheim, and a grant to the Diffuse Lung Diseases Research Group from the Ministry of Health, Labour and Welfare, Japan.

Author information

Author notes

  1. Tomotsugu Takano and Kazuya Tsubouchi contributed equally to this work.

Authors and Affiliations

  1. Department of Respiratory Medicine, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan

    Tomotsugu Takano, Kazuya Tsubouchi & Isamu Okamoto

  2. Department of Respiratory Medicine, Fukuoka University School of Medicine, Fukuoka, Japan

    Naoki Hamada & Masaki Fujita

  3. Kirigaoka Tsuda Hospital, Kitakyushu, Japan

    Katsuyuki Ichiki

  4. Department of Respiratory Medicine, Wakamatsu Hospital of the University of Occupational and Environmental Health Japan, Kitakyushu, Japan

    Ryo Torii

  5. Department of Respiratory Diseases, NHO Fukuokahigashi Medical Center JP, Fukuoka, Japan

    Shohei Takata

  6. Division of Respiratory Medicine, Kyushu Rosai Hospital, Kitakyushu, Japan

    Satoru Kawakami

  7. Department of Respiratory Medicine, Japanese Red Cross Fukuoka Hospital, Fukuoka, Japan

    Noriaki Nakagaki

  8. Department of Respiratory Diseases, NHO Fukuoka National Hospital JP, Fukuoka, Japan

    Makoto Yoshida

  9. Department of Respiratory Medicine, Japan Community Health Care Organization Kurume General Hospital, Kurume, Japan

    Yasuhiko Kitasato

  10. Division of Respiratory Medicine, Aso Iizuka Hospital, Iizuka, Japan

    Kazunori Tobino

  11. Department of Respiratory Medicine, Kitakyushu Municipal Medical Center, Kitakyushu, Japan

    Eiji Harada

  12. Department of Respiratory Medicine, Fukuoka University Chikushi Hospital, Chikushino, Japan

    Hiroshi Ishii

  13. Department of Respiratory Medicine, Saiseikai Fukuoka General Hospital, Fukuoka, Japan

    Hiroshi Wataya

  14. Department of Respiratory Medicine, Hamanomachi Hospital, Fukuoka, Japan

    Takashige Maeyama

  15. Department of Respiratory Medicine, University of Occupational and Environmental Health Japan, Kitakyushu, Japan

    Kazuhiro Yatera

  16. Division of Respirology, Neurology, and Rheumatology, Department of Internal Medicine, Kurume University School of Medicine, Kurume, Fukuoka, Japan

    Masaki Okamoto

  17. Department of Respirology, NHO Kyushu Medical Center, Fukuoka, Japan

    Masaki Okamoto

  18. Department of Health Sciences, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan

    Hidetake Yabuuchi

  19. Clinical Research Support Center Kyushu, Fukuoka, Japan

    Fumiaki Kiyomi

  20. Medical Information Center, Kyushu University Hospital, Fukuoka, Japan

    Shoji Tokunaga

  21. Kitakyushu City Hospital Organization, Kitakyushu, Japan

    Yoichi Nakanishi

Authors
  1. Tomotsugu Takano
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  2. Kazuya Tsubouchi
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  23. Isamu Okamoto
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Contributions

TT and KT equally contributed to this work. TT, KTsubouchi and IO contributed to the literature search, figures, the study design, data collection, data analysis, data interpretation, and writing approved the final version of the review. NH and YN contributed to the literature search, study design, data collection, and data interpretation and approved the final version of the review. FK and STokunaga contributed to the literature search, figures, data analysis, and writing and approved the final version of the review. KI, RT, STakata, SK, NN, MY, YK, KTobino, EH, HI, HW, TM, MF, KY and MO contributed to the literature search, data collection, and data interpretation and approved the final version of the review. HY contributed to the literature search, data analysis, and writing, and approved the final version of the review. IO accepts full responsibility for the work and/or conduct of the study, has access to the data and controls the decision to publish.

Corresponding author

Correspondence to Isamu Okamoto.

Ethics declarations

Ethics approval and consent to participate

This study involves human participants and this prospective, multi-center　observational study was approved by the Institutional Review Board of Kyushu University (#25–135, August 23, 2013; #555-00, August 27, 2013) and by the institutional review boards of all participating hospitals. Participants provided informed consent before participating in the study.

Consent for publication

Not applicable since there are no details on individuals reported within the manuscript.

Competing interests

STakata has received personal fees from AstraZeneca, Nippon Boehringer Ingelheim, Novartis, GSK, and Teijin Pharma. KY has received personal fees from Nippon Boehringer Ingelheim, GSK and Teijin Pharma. MO has received personal fees from Nippon Boehringer Ingelheim. IO has received personal fees from AstraZeneca, Nippon Boehringer Ingelheim and Novartis.

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Takano, T., Tsubouchi, K., Hamada, N. et al. Update of prognosis and characteristics of chronic obstructive pulmonary disease in a real-world setting: a 5-year follow-up analysis of a multi-institutional registry. BMC Pulm Med 24, 556 (2024). https://doiorg.publicaciones.saludcastillayleon.es/10.1186/s12890-024-03347-5

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  • DOI: https://doiorg.publicaciones.saludcastillayleon.es/10.1186/s12890-024-03347-5

Keywords

BMC Pulmonary Medicine

ISSN: 1471-2466

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