EPIDEMIOLOGY OF RESPIRATORY SYMPTOMS, LUNG-FUNCTION AND IMPORTANT DETERMINANTS - REPORT FROM THE BSTRUCTIVE-LUNG-DISEASE-IN-NORTHERN-SWEDEN-PROJECT

Setting: Cross-sectional epidemiological study based on a representati ve sample of the general population in northern Sweden. Objectives: To assess the prevalence of respiratory symptoms, the role of respirator y symptoms as indicators of impairment of lung function, and to define risk factors for respiratory symptoms and lung function impairment. D esign: The 1340 subjects of 6610 who reported respiratory symptoms sug gestive of asthma or chronic bronchitis in a postal questionnaire stud y were invited to a structured interview and lung function tests. A co ntrol group of 315 subjects was also invited. Risk factors were assess ed from the postal questionnaire. Results: 400 subjects in the symptom atic group had attacks of breathlessness and wheezing, while none in t he control group had them, corresponding to 7% of the original study p opulation. Chronic productive cough was present in 537 subjects, of wh om 13 were from the control group, suggesting that 12% of the original study population had this symptom. Persistent wheeze was the symptom that predicted the greatest proportion of cases of impaired lung funct ion. Attacks of breathlessness, wheezing, long-standing cough and sput um production were all related to age, smoking and a family history of asthma. Both chronic productive cough and impaired lung function corr elated strongly with smoking and age, and their prevalences differed i n different socio-economic groups. Conclusion: Impaired lung function can be predicted from respiratory symptoms. Data collected in postal q uestionnaires suffice for the identification of risk factors. Combinat ions of symptoms gave greater odds ratios than individual symptoms.