Asthma and COPD Overlap Syndrome (ACOS): A Systematic Review and Meta Analysis.
BACKGROUND
The combination of asthma and chronic obstructive pulmonary disease (COPD), or ACOS is a recently defined syndrome. The epidemiology of the condition is poorly described and previous research has suggested ACOS is associated with worse outcomes than either condition alone. We therefore decided to complete a systematic review of the published literature.


METHODS
This review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta- Analyses guidelines. A structured search was performed in the PubMed, Embase, and Medline databases up to Feb 2015 to identify studies reporting incidence, prevalence, health care utilization, morbidity, or mortality in COPD and asthma.


RESULTS
A total of 19 studies were included in the present study. The pooled prevalence of overlap among COPD was 27% (95% CI: 0.16-0.38, p<0.0001) and 28% (95% CI: 0.09-0.47, p = 0.0032) in the population and hospital-based studies, respectively. We found no significant difference between ACOS and COPD in terms of gender, smoking status, lung function and 6mWD. However, in comparison to subject with only COPD, ACOS subjects were significantly younger, had higher BMI, healthcare utilization, and lower HRQoL.


CONCLUSIONS
ACOS is a common condition that exists in a substantial proportion of subjects with COPD. ACOS represents a distinct clinical phenotype with more frequent exacerbations, hospitalization, worse health-related quality of life, and higher healthcare costs than either disease alone. There is a critical need to better define the management and treatment of this syndrome.
Department of Experimental Medicine, The University of British Columbia, Vancouver, British Columbia, Canada.
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Alshabanat
Centre for Clinical Epidemiology and Evaluation, Vancouver Coastal Health Institute, Vancouver, British Columbia, Canada.
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Zafari
Department of Medicine, King Fahad Specialist Hospital, Dammam, Saudi Arabia.
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Albanyan
Department of Medicine, The University of British Columbia, Vancouver, British Columbia, Canada.
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Dairi
Centre for Clinical Epidemiology and Evaluation, Vancouver Coastal Health Institute, Vancouver, British Columbia, Canada; Institute for Heart and Lung Health (IHLH), Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada.
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FitzGerald
D001249:Asthma / Q000150:complications* / Q000188:drug therapy / Q000503:physiopathology; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D006801:Humans; D029424:Pulmonary Disease, Chronic Obstructive / Q000150:complications* / Q000188:drug therapy / Q000503:physiopathology; D011788:Quality of Life; D012129:Respiratory Function Tests; D012907:Smoking / Q000503:physiopathology