[Epidemiological study of chronic obstructive pulmonary disease in Spain (IBERPOC): prevalence of chronic respiratory symptoms and airflow limitation]. / Estudio IBERPOC en España: prevalencia de síntomas respiratorios habituales y de limitación crónica al flujo aéreo.

The prevalence of chronic respiratory symptoms and chronic airflow limitation (CAFL) was determined in a multicentric epidemiological study carried out in seven different areas of Spain. Based on a target population of 236,412 persons, a random census sample of 4,035 individuals between 40 and 69 years of age was chosen. Subjects answered several questionnaires and performed spirometric tests followed by a bronchodilation test if bronchial obstruction was detected. Respiratory symptoms were reported by 48% of the population (95% CI: 46.4-49.5%) with greater frequency of symptoms among men than women (55.2% versus 41%, p < 0.001). The following levels of prevalence of chronic symptoms were found: cough, 13.5% (95% CI: 12.5-14.6%); expectoration, 10.7% (95% CI: 9.7-11.6%); dyspnea after one flight of stairs, 10.4% (95% CI: 9.5-11.4%); and wheezing, 40.2% (95% CI: 38.7-41.7%). The prevalence of chronic bronchitis (CB) was 4.8% (95% CI: 4.1-5.4%) and was more frequent among men than among women (8.3% and 1.4%, respectively; p < 0.001). Asthma had been diagnosed previously in 4.9% (95% CI: 4.2-5.5%), more often in women than in men (5.8% and 3.8%, respectively; p < 0.003). CAFL was found in 10.6% (95% CI: 9.6-11.5%), 15.8% in men and 5.5% in women (p < 0.001). All respiratory symptoms except asthma were more frequent among smokers than among ex-smokers, and in turn were more common among ex-smokers than non-smokers. The frequency of symptoms increased in accordance with accumulated smoking. The prevalence of CB and CAFL was vastly different from one region to another. Multivariate analysis showed that factors associated independently with the appearance of CB were smoking, age over 60 years, male sex and having worked in industry. In conclusion, respiratory symptoms, including CB and CAFL, are common in the Spanish population. Smoking and amount of smoking are directly related to the frequency of such symptoms. Substantial differences were found in the prevalence of CB and CAFL among the regions where the study was performed.