Clinical epidemiology of chronic obstructive pulmonary disease; [Epidemiologia clínica da doença pulmonar obstrutiva crónica]

Abstract

Chronic obstructive pulmonary disease (COPD) is responsible for early morbidity and high mortality and significant costs to health systems. Smoking remains the main risk factor for COPD but additional factors, such as indoor and outdoor air pollution, occupational exposure and genetic susceptibility are increasingly recognized. Th e burden of COPD has been difficult to estimate owing to the multiple definitions applied, with variations between estimates of prevalence exceeding 15%. Definitions based on objective spirometric measurements have yielded higher prevalence estimates than patients' self-report of a clinical diagnosis of COPD. Th e Global Initiative for Chronic Obstructive Lung Disease (GOLD) proposed a physiologic definition of COPD characterized by airflow limitation that is not fully reversible (post-bronchodilator FEV1/FVC < 0.70). Many authors have argued against this fixed ratio definition and advocate the use of a "lower limit of normal" criterion to define COPD in order to avoid overdiagnosis of the disease in the elderly. Despite controversies, the definition proposed by GOLD is unambiguous, easily remembered by clinicians, reproducible in different settings and suitable for cross-sites comparisons. Recently, two multinational studies adopted the GOLD definition to provide standardized population-based estimates of the prevalence of COPD in adults aged 40 years or over throughout the world. These estimates varied between 11.4 and 26.1% in the international BOLD study and between 2.6% and 7.1% in the five Latin American cities of the PLATINO study. Although debate on COPD definition is ongoing, the burden of the disease is high and growing. The major challenge in coming years will be to stop the smoking epidemic, particularly in developing countries, and to increase physician knowledge of the disease favouring an early diagnosis.