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      Clinical characteristics of the asthma–COPD overlap syndrome – a systematic review

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          Background and objective

          In recent years, the so-called asthma–chronic obstructive pulmonary disease (COPD) overlap syndrome (ACOS) has received much attention, not least because elderly individuals may present characteristics suggesting a diagnosis of both asthma and COPD. At present, ACOS is described clinically as persistent airflow limitation combined with features of both asthma and COPD. The aim of this paper is, therefore, to review the currently available literature focusing on symptoms and clinical characteristics of patients regarded as having ACOS.


          Based on the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines, a systematic literature review was performed.


          A total of 11 studies met the inclusion criteria for the present review. All studies dealing with dyspnea (self-reported or assessed by the Medical Research Council dyspnea scale) reported more dyspnea among patients classified as having ACOS compared to the COPD and asthma groups. In line with this, ACOS patients have more concomitant wheezing and seem to have more cough and sputum production. Compared to COPD-only patients, the ACOS patients were found to have lower FEV 1% predicted and FEV 1/FVC ratio in spite of lower mean life-time tobacco exposure. Furthermore, studies have revealed that ACOS patients seem to have not only more frequent but also more severe exacerbations. Comorbidity, not least diabetes, has also been reported in a few studies, with a higher prevalence among ACOS patients. However, it should be acknowledged that only a limited number of studies have addressed the various comorbidities in patients with ACOS.


          The available studies indicate that ACOS patients may have more symptoms and a higher exacerbation rate than patients with asthma and COPD only, and by that, probably a higher overall respiratory-related morbidity. Similar to patients with COPD, ACOS patients seem to have a high occurrence of comorbidity, including diabetes. Further research into the ACOS, not least from well-defined prospective studies, is clearly needed.

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          Most cited references 26

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          Global strategy for the diagnosis, management and prevention of COPD

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            Increased risk of exacerbation and hospitalization in subjects with an overlap phenotype: COPD-asthma.

            Several COPD phenotypes have been described; the COPD-asthma overlap is one of the most recognized. The aim of this study was to evaluate the prevalence of three subgroups (asthma, COPD, and COPD-asthma overlap) in the Latin American Project for the Investigation of Obstructive Lung Disease (PLATINO) study population, to describe their main characteristics, and to determine the association of the COPD-asthma overlap group with exacerbations, hospitalizations, limitations due to physical health, and perception of general health status (GHS). The PLATINO study is a multicenter population-based survey carried out in five Latin American cities. Outcomes were self-reported exacerbations (defined by deterioration of breathing symptoms that affected usual daily activities or caused missed work), hospitalizations due to exacerbations, physical health limitations, and patients' perception of their GHS obtained by questionnaire. Subjects were classified in three specific groups: COPD--a postbronchodilator (post-BD) FEV₁/FVC ratio of < 0.70; asthma--presence of wheezing in the last year and a minimum post-BD increase in FEV₁ or FVC of 12% and 200 mL; and overlap COPD-asthma--the combination of the two. Out of 5,044 subjects, 767 were classified as having COPD (12%), asthma (1.7%), and COPD-asthma overlap (1.8%). Subjects with COPD-asthma overlap had more respiratory symptoms, had worse lung function, used more respiratory medication, had more hospitalization and exacerbations, and had worse GHS. After adjusting for confounders, the COPD-asthma overlap was associated with higher risks for exacerbations (prevalence ratio [PR], 2.11; 95% CI, 1.08-4.12), hospitalizations (PR, 4.11; 95% CI, 1.45-11.67), and worse GHS (PR, 1.47; 95% CI, 1.18-1.85) compared with those with COPD. The coexisting COPD-asthma phenotype is possibly associated with increased disease severity.
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              The Coexistence of Asthma and Chronic Obstructive Pulmonary Disease (COPD): Prevalence and Risk Factors in Young, Middle-aged and Elderly People from the General Population

              Background The joint distribution of asthma and chronic obstructive pulmonary disease (COPD) has not been well described. This study aims at determining the prevalence of self-reported physician diagnoses of asthma, COPD and of the asthma-COPD overlap syndrome and to assess whether these conditions share a common set of risk factors. Methods A screening questionnaire on respiratory symptoms, diagnoses and risk factors was administered by mail or phone to random samples of the general Italian population aged 20–44 (n = 5163) 45–64 (n = 2167) and 65–84 (n = 1030) in the frame of the multicentre Gene Environment Interactions in Respiratory Diseases (GEIRD) study. Results A physician diagnosis of asthma or COPD (emphysema/chronic bronchitis/COPD) was reported by 13% and 21% of subjects aged <65 and 65–84 years respectively. Aging was associated with a marked decrease in the prevalence of diagnosed asthma (from 8.2% to 1.6%) and with a marked increase in the prevalence of diagnosed COPD (from 3.3% to 13.3%). The prevalence of the overlap of asthma and COPD was 1.6% (1.3%–2.0%), 2.1% (1.5%–2.8%) and 4.5% (3.2%–5.9%) in the 20–44, 45–64 and 65–84 age groups. Subjects with both asthma and COPD diagnoses were more likely to have respiratory symptoms, physical impairment, and to report hospital admissions compared to asthma or COPD alone (p<0.01). Age, sex, education and smoking showed different and sometimes opposite associations with the three conditions. Conclusion Asthma and COPD are common in the general population, and they coexist in a substantial proportion of subjects. The asthma-COPD overlap syndrome represents an important clinical phenotype that deserves more medical attention and further research.

                Author and article information

                Int J Chron Obstruct Pulmon Dis
                Int J Chron Obstruct Pulmon Dis
                International Journal of COPD
                International Journal of Chronic Obstructive Pulmonary Disease
                Dove Medical Press
                27 July 2015
                : 10
                : 1443-1454
                [1 ]Department of Pulmonary Medicine, Hvidovre Hospital, Copenhagen, Denmark
                [2 ]University of Copenhagen, Copenhagen, Denmark
                Author notes
                Correspondence: Charlotte Suppli Ulrik, Department of Pulmonary Medicine, 253 Hvidovre Hospital, DK-2650 Hvidovre, Denmark, Email csulrik@
                © 2015 Nielsen et al. This work is published by Dove Medical Press Limited, and licensed under Creative Commons Attribution – Non Commercial (unported, v3.0) License

                The full terms of the License are available at Non-commercial uses of the work are permitted without any further permission from Dove Medical Press Limited, provided the work is properly attributed.


                Respiratory medicine

                characteristics, symptoms, copd, asthma, acos


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