Airway obstruction in relation to symptoms in chronic respiratory disease--a nationally representative population study.

We examined the severity of airway obstruction and the occurrence of respiratory symptoms in a large, nationally representative population sample and in a subgroup of subjects with chronic bronchitis and/or emphysema to obtain information for developing national prevention and treatment strategies for these diseases. The study population comprised of 7217 randomly selected subjects (aged 30 years and older) who participated in a comprehensive health examination survey. The 'cases' were subjects diagnosed as having chronic bronchitis and/or emphysema. The survey methods comprised of questionnaires, interviews, physical measurements, including spirometry, and clinical examinations. In the whole study population, the age-adjusted prevalence of chronic bronchitis and/or emphysema was 22% among men and 7% among women, whilst clinically relevant airways obstruction (FEV1/FVC%< or = 69) was present in 11% of men and in 5% of women. The occurrence of chronic cough and phlegm production was lowest among the 'cases' with pronounced obstruction (in 68% of men with severe and in 60% of women with moderate obstruction), whereas cold air-associated dyspnoea aggravation showed an inverse relationship, occurring most commonly in men (80%) with severe obstruction. Unexpectedly, half of the bronchitic women had never smoked. We conclude that the occurrence of certain bronchitic symptoms, such as chronic cough and phlegm production and cold air-associated dyspnoea aggravation, may to some degree indicate different stages of the disease. Smoking was not closely associated with airflow limitation in women here.