In a recent study published in BMC Public Health, a group of researchers estimated the global and regional prevalence of Chronic Obstructive Pulmonary Disease (COPD) in individuals aged 40 and above, using spirometry and comparing two diagnostic criteria: fixed ratio (FR) and lower limit of normal (LLN).
Study: Estimating the global prevalence of chronic obstructive pulmonary disease (COPD): a systematic review and meta-analysis. Image Credit: mi_viri/Shutterstock.com
COPD, a leading cause of death globally, is a heterogeneous lung disease marked by chronic respiratory symptoms and airflow limitation. In 2016, 251 million cases were reported worldwide, with mortality rates increasing by 35.4% from 2009 to 2019.
COPD, affecting both smokers and non-smokers, is linked to various risk factors like air pollution, occupational exposures, and genetic predispositions. Underdiagnosis is common, often due to insufficient knowledge and underuse of spirometry, the gold standard for diagnosis.
Further research is needed to enhance understanding, improve diagnosis and treatment strategies, and effectively address the evolving global burden of COPD.
About the study
The present review adhered to the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines. It included studies that reported the prevalence of COPD in individuals aged 40 and above, using spirometry testing and were published in English or French between 2016 and 2022.
The literature search encompassed Web of Sciences, MEDLINE, and Scopus databases, using keywords like "COPD," "prevalence," and "epidemiology."
Initial study selection was based on titles and abstracts, with a further review of full texts for ambiguous cases. Two postgraduate students and two professors executed this selection process. Additionally, reference lists of chosen studies were manually examined for potential inclusions.
Data from the studies were extracted onto a Microsoft Excel form, capturing details like study design, location, diagnostic criteria, objectives, COPD, and results.
The Strengthen The Reporting of Observational Studies in Epidemiology (STROBE) checklist was employed for quality assessment of the studies, assigning scores based on criteria like study objective clarity, lung function measurement, sampling technique, sample size, and diagnostic criteria.
Given the diverse nature of the studies, a random-effect meta-analysis was conducted. Inter-study heterogeneity was assessed using the I2 test, with values over 70% indicating high variability. Forest plots displayed COPD prevalence based on FR and LLN diagnostic criteria.
Meta-regression was used to analyze COPD prevalence by various parameters and identify heterogeneity sources. Sensitivity analysis examined the impact of heavily weighted studies on overall results. MedCalc version 19.4 was the tool for meta-analysis, and Egger’s test evaluated potential biases by examining funnel plot symmetry.
The team identified 3,993 potentially relevant records in this systematic review and meta-analysis through database searches. After removing duplicates and screening based on titles and abstracts, 384 articles were examined in full text, including 42 studies.
These studies were all published in English between 2016 and 2022, mostly employing a cross-sectional design. The geographic distribution of these studies was diverse, covering twenty-three countries across various World Health Organization (WHO) regions, with the Western Pacific region being the most represented.
The studies involved a total of 339,475 participants aged 40 years and older, with a mean age of 57.30 years. The diagnostic criteria for COPD varied, with twelve studies using FR and LLN criteria.
Quality assessment revealed that half of the studies were high quality, and the other half were moderate. None were categorized as low quality. The overall prevalence of COPD among individuals aged 40 and above was found to be 12.64% according to FR criteria and 7.38% according to LLN criteria.
Men showed a higher prevalence than women in FR criteria, but similar rates were observed in both sexes under LLN criteria. Stage II COPD was the most common stage identified.
The prevalence of COPD increases with age regardless of the diagnostic criteria used. In the age group of 40-49 years, the prevalence was 4.37% (FR criteria) and 5.22% (LLN criteria), which increased significantly in those aged 70 and above.
Smokers exhibited a higher prevalence compared to non-smokers, with current smokers having the highest prevalence under both criteria.
Regionally, the American region had the highest prevalence according to FR criteria, while the Southeast Asian region led according to LLN criteria. The African region had the least studies, particularly under FR criteria.
An interesting trend was observed in the prevalence over time; there was a significant increase from 2016-2019 to 2020-2022 under FR criteria but a slight decrease under LLN criteria.
Regarding publication bias, the limited number of studies constrained a comprehensive assessment. However, where possible, an asymmetric funnel plot suggested the presence of publication bias in various determinants related to both FR and LLN criteria. Egger’s test confirmed these findings, indicating a need for caution in interpreting these results.