Prevalence and risk factors for chronic obstructive pulmonary disease according to symptoms and spirometry

The burden of COPD is quite high and its prevalence is increasing. Few data are available from Latin America. There is no consensus on what criteria should be the gold standard for the definition of this disease. A population-based study was carried out in a southern Brazilian city, including adults aged 40-69 years. The aim was to measure the prevalence of COPD according to several criteria. From the 1,046 subjects chosen from a multiple-stage sampling protocol, a sub-sample of 234 subjects was systematically selected to undergo spirometry. Percentages of COPD according to different criteria were: chronic bronchitis by questionnaire (7.8%); GOLD stage 0 (7.3%); fixed ratio (15.2%); GOLD stage II (9.9%); ERS (27.7%). The relationship among the three lung functional measurements showed that around 70% of all subjects had negative results with all three criteria, and around 10% were positive according to all three. Utilization of symptom-based or spirometry definitions of COPD provide different prevalence estimates. Use of different spirometric criteria also resulted in different percentages of COPD. According to spirometry, COPD was higher among men, elderly, those with low education and ex-smokers. On the other hand, current smokers were more likely to present symptoms of chronic bronchitis. The fixed ratio criterion is recommended when population-specific reference curves are not available, while the GOLD definition is recommended to evaluate severity of COPD.