A systematic review and meta-analysis of global prevalence estimates for chronic obstructive pulmonary disease (COPD) from 1990 to 2004 found that the pooled prevalence of COPD in adults aged ≥40 years is 7.6%, with 6.4% for chronic bronchitis and 1.8% for emphysema. Spirometric estimates, using the Global Initiative for Chronic Obstructive Lung Disease (GOLD) criteria, yielded a pooled prevalence of 8.9%. However, significant heterogeneity was observed, which was not fully explained by subgroup analysis. Regional gaps and methodological differences hindered interpretation of the data. The prevalence of physiologically defined COPD in adults aged ≥40 years is estimated at 9–10%, with higher rates in smokers, males, and urban residents. The study highlights the need for standardized measurement methods to improve understanding of COPD's global burden. Despite the importance of COPD, prevalence estimates remain inconsistent due to varying diagnostic criteria, smoking patterns, and age ranges. Efforts by organizations like the GOLD initiative aim to standardize COPD prevalence measurement, improving global health planning and public health strategies. The study underscores the importance of accurate prevalence data for assessing disability, quality of life, and healthcare costs associated with COPD.A systematic review and meta-analysis of global prevalence estimates for chronic obstructive pulmonary disease (COPD) from 1990 to 2004 found that the pooled prevalence of COPD in adults aged ≥40 years is 7.6%, with 6.4% for chronic bronchitis and 1.8% for emphysema. Spirometric estimates, using the Global Initiative for Chronic Obstructive Lung Disease (GOLD) criteria, yielded a pooled prevalence of 8.9%. However, significant heterogeneity was observed, which was not fully explained by subgroup analysis. Regional gaps and methodological differences hindered interpretation of the data. The prevalence of physiologically defined COPD in adults aged ≥40 years is estimated at 9–10%, with higher rates in smokers, males, and urban residents. The study highlights the need for standardized measurement methods to improve understanding of COPD's global burden. Despite the importance of COPD, prevalence estimates remain inconsistent due to varying diagnostic criteria, smoking patterns, and age ranges. Efforts by organizations like the GOLD initiative aim to standardize COPD prevalence measurement, improving global health planning and public health strategies. The study underscores the importance of accurate prevalence data for assessing disability, quality of life, and healthcare costs associated with COPD.