In a recently published study, Dr BMC Public HealthA group of researchers estimated global and regional prevalence of chronic obstructive pulmonary disease (COPD) in individuals aged 40 years and older using spirometry and comparing two diagnostic criteria: specific 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 worldwide, is a heterogeneous lung disease characterized by chronic respiratory symptoms and airflow limitation. In 2016, 251 million cases were reported worldwide, with a 35.4% increase in mortality from 2009 to 2019.
COPD, affecting both smokers and non-smokers, is associated with various risk factors such as air pollution, occupational exposures and genetic predisposition. Diagnosis is common, often due to insufficient knowledge and the inadequacy of spirometry, the gold standard for diagnosis.
More research is needed to increase understanding, improve diagnosis and treatment strategies, and effectively address the growing global burden of COPD.
About the study
The current review adheres to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines It included studies reporting on the prevalence of COPD in individuals aged 40 years and older using spirometry testing and published in English or French between 2016 and 2022.
The literature search included the Web of Science, Medline, and Scopus databases using keywords such as “COPD,” “prevalence,” and “epidemiology.”
Primary study selection was based on titles and abstracts, with further review of full texts for unclear cases. Two graduate students and two professors conducted the selection process. In addition, reference lists of selected studies were manually checked for possible inclusion.
Data from studies were extracted into a Microsoft Excel form, capturing details such as study design, location, diagnostic criteria, objectives, COPD and outcomes.
The STRENGTHENING Reporting of Observational Studies in Epidemiology (STROBE) checklist was employed to assess study quality, assigning scores based on criteria such as study objective clarity, lung function measurement, sampling technique, sample size, and diagnostic criteria.
Given the heterogeneous nature of the studies, a random-effects meta-analysis was conducted. Inter-study heterogeneity was assessed using I2 test, indicating high variability with values greater than 70%. Forest plots displayed the prevalence of COPD based on FR and LLN diagnostic criteria.
Meta-regression was used to analyze COPD prevalence by various parameters and identify sources of variation. Sensitivity analysis examined the effect of heavily weighted studies on overall results. MedCalc version 19.4 was the meta-analysis tool, and Egger’s test assessed potential bias by testing funnel plot symmetry.
Results of the study
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 including 42 studies were examined in full text.
These studies were published in English between 2016 and 2022, most employing a cross-sectional design. The geographic distribution of these studies was diverse, covering 23 countries across different World Health Organization (WHO) regions, with the Western Pacific region being the most represented.
The study involved a total of 339,475 participants aged 40 years and older, with a mean age of 57.30 years. Diagnostic criteria for COPD varied, with twelve studies using FR and LLN criteria.
Quality assessment revealed that half of the studies were of high quality, and the other half moderate. None were classified as low quality. The overall prevalence of COPD among individuals aged 40 years and above was found to be 12.64% by FR criteria and 7.38% by LLN criteria.
Males showed a higher prevalence than females under the FR criteria, but similar rates were observed in both sexes under the LLN criteria. Stage II COPD was identified as the most common stage.
The prevalence of COPD increases with age regardless of the diagnostic criteria used. Between the ages of 40–49 years, the prevalence was 4.37% (FR criteria) and 5.22% (LLN criteria), which increased significantly among those aged 70 years and older.
Smokers demonstrated a higher prevalence than nonsmokers, with current smokers having the highest prevalence under both criteria.
Regionally, the American region had the highest expansion by FR criteria, while the Southeast Asian region led by the LLN criteria. The African region has had the fewest studies, especially under FR criteria.
An interesting trend prevalent over time was observed; There was a significant increase from 2016-2019 to 2020-2022 under the FR criteria but a slight decrease under the LLN criteria.
Regarding publication bias, the limited number of studies limits a comprehensive evaluation. However, where possible, an asymmetric funnel plot suggested the presence of publication bias in different determinants related to both FR and LLN criteria. Egger’s experiment confirmed these results, indicating the need for caution in interpreting these results.