This report details the prevalence of COPD and its clinical features using a nationwide database of COPD patients. We found that a considerable number of COPD patients who were hospitalised for acute exacerbation eventually went through repeated hospitalisations. We also demonstrated that a number of patient-related and clinical factors were associated with readmission, including sex, higher comorbidity burden, medical aid coverage, duration of systemic steroid use during index hospitalisation.
Each year, COPD is responsible for as many as 800,000 hospitalisations, and approximately 20% of patients experience rehospitalisation within 30 days of discharge[8, 12]. It is estimated that nearly 50 billion dollars are spent on COPD-related healthcare expenditure annually, and rehospitalisation-related healthcare costs alone account for over 15 billion dollars in the United States[6, 13]. Considering the social and financial impact of rehospitalisation in COPD patients, there have been several clinical trials [14–16] for developing a COPD-specific risk stratification tool to predict patients who are at high risk of readmission or interventions to reduce rehospitalisation. However, no such tool has been found to be effective. Boourbeau et al., and Casas et al., reported interventions that focused on disease-specific programmes (e.g., COPD education and teaching inhaler use) and post-discharge programmes (e.g., home visits, telephone call and patient hotline) to reduce rehospitalisation. Notably, they only focused on reducing rehospitalisations at 12 months and not on decreasing early rehospitalisation as the endpoint. On the other hand, Fan et al., reported termination of clinical trial due to unanticipated excess mortality in an intervention group received COPD care program including education. In addition to the heterogeneity of study designs, many trials have dealt with the effectiveness of post-discharge interventions that may not have consistent results.
Under these circumstances, the Hospital Readmission Reduction Programme (HRRP) included AECOPD as a targeted medical condition. In response to the HRRP, Ohar JA et al., performed a retrospective observational cohort study and reported that a comprehensive care plan for AECOPD admission reduced all-cause readmission and mortality at 30 days from discharge. This implies that an effective intervention could improve outcomes for COPD patients. However, before the implementation of an intervention, it is necessary to find and validate the causes of readmission and predictors in a large cohort and to develop an individual-focused readmission risk stratification tool.
Recently, David et al., analysed a nationwide readmission database for AECOPD in accordance with the HRRP, and found early readmission within 30 days after index AECOPD admission was associated with both patient-related factors (Medicaid payer status, low household income, and more comorbid condition) and clinical factors (longer hospital stay and discharge to a skilled nursing facility). Similarly, these factors were reconfirmed in our study using another nationwide database. In addition, our study found that sex and systemic steroid use significantly influenced rehospitalisation. The effect of sex on susceptibility to readmission after AECOPD is controversial. Ryan et al., reported that the male sex was one of the risk factors for death and rehospitalisation after a severe event of AECOPD. Similarly, other studies have shown that the male sex has a negative effect on COPD outcomes. However, some have suggested that males have a lower risk of adverse outcomes from COPD than females. Although the characteristics and prognosis of COPD patients by sex have not been fully elucidated, susceptibility to toxic inhalation, airway structures, and female sex hormone have been identified as relevant factors[22, 23]. Recommendations for the management of COPD include systemic steroid treatment for 5 to 7 days and a daily dose of 40 mg prednisone. Although the mechanisms for clinical improvement of lung function, oxygenation, and outcomes (i.e., early relapse, treatment failure, and length of hospitalisation) among patients who are administered corticosteroids during exacerbation events have not been fully elucidated, reduction in airway inflammation or decrease in airway oedema may be contributing factors. We reported interesting results for association between corticosteroids and early readmission in AECOPD patients, by showing that corticosteroid use for more than 5 days was associated with an increased risk of rehospitalisation. Our results correspond to recent meta-analysis results and recommendations that long-term corticosteroid use during hospitalisation has no benefit compared with short-term use.
This is the first study to report on the status and related predictors of AECOPD rehospitalisation using a nationwide healthcare database in Korea. Although the prevalence of readmission was relatively high, predictors of rehospitalisation in this study were similar to those in David et al.’s study. However, we further discovered that the use of systemic steroids was a significant factor associated with readmission.
Respiratory reasons account for 57% of readmissions and were the most common causes of readmission for COPD-related events regardless of both age and sex. Cardiac causes of readmission included heart failure, ischaemic heart disease and arrhythmias, which cumulatively accounted for 3% of readmissions. The remaining 40% of readmissions were due to conditions other than respiratory and cardiac causes. We evaluated the natural course (up to 30 days) of patients who were discharged after acute exacerbation of COPD, and found that there were some differences in the pattern of occurrence depending on the cause of readmission. In particular, respiratory causes of readmission showed a pattern similar to that of all causes of readmission, accounting for more than half of the events (51.7%) that occurred within 10 days of discharge. The occurrence of events gradually decreased after this period. On the other hand, majority of cardiac cause-related readmissions (48.5%) also occurred within 10 days of discharge, but even after 3 weeks of discharge, more than 10% of events occurred and there was no pattern of gradual decrease. Congestive heart failure (CHF) has been reported to be the most common readmission diagnosis after respiratory-based disease,[8, 9] and also one-fifth of COPD patients have been known to have unrecognised coexisting heart failure. Unlike previous studies, we reported that the cardiac reasons for readmission after AECOPD in Korea accounted for as low as 3% of patients. Nationwide data have shown that Korean COPD patients have a lower body mass index, lower comorbid hypertension and dyslipidaemia, which are known as risk factors for cardiac disease, and a lower prevalence of myocardial infarct than other races or ethnic groups. Similarly, low rates of cardiac cause-related readmissions may be due to racial differences. Additionally, it is not easy to distinguish symptoms and signs between heart failure and AECOPD in actual clinical practice. Thus, the clinical manifestations of heart failure commonly mimic those of AECOPD. Since there is no acceptable biomarker for COPD, unlike cardiac troponin in ischaemic heart disease and B-type natriuretic peptide in CHF, this overlap of symptoms and signs makes diagnosis difficult and complicates coding of the diagnosis at the time hospitalisation. Even readmission in patients with COPD is a very complex phenomenon considering various well-known comorbidities. A single disease-specific approach for prediction is probably not sufficient, especially since readmission itself in COPD patients is related to high healthcare costs and adverse outcomes.
This study has a strong advantage since it can be generalised; we could analyse medical claim data for all citizens due to the unique nature of the health insurance system in Korea. However, when interpreting the results of this study, some limitations should be considered. First, our study was based on the HIRA database and was observational and retrospective. Although a nationwide database provides a large sample size and various clinical data related to hospitalisation and discharge, we did not include clinically important biomarkers for prediction of readmission risk such as forced expiratory volume in 1 second, body mass index and severity of dyspnoea. Second, our 30-day readmission rate was relatively high compared with previous studies, possibly due to the relatively easy accessibility to medical care in Korea. Lastly, biases in estimating health care utilisation and cause of readmission may be present because we used the ICD-10 code for defining hospitalisation and readmission.