Prevalence of obstructive lung diseases and respiratory symptoms in relation to living environment and socio-economic group

We wanted to test whether living environment, occupation and social position are risk factors for asthma and chronic bronchitis/emphysema (CBE). The prevalence of bronchial asthma, CBE, respiratory symptoms and smoking habits in a random sample of 12071 adults aged 20–59 years was assessed in a postal survey with a slightly modified questionnaire previously used in central and northern Sweden (The OLIN studies). Occupation was coded according to a socio-economic classification system. Six different living environment areas were defined; city–countryside, seaside–not seaside and living close to heavy traffic-not living close to heavy traffic. Multiple logistic regression analysis (forward conditional) was applied to estimate the association between the proposed set of risk factors and self-reported obstructive lung diseases and lower respiratory symptoms controlling for age, gender and smoking. After two reminders, the response rate was 70·1% (n=8469); 33·8% of the responders were smokers. In all, 469 subjects (5·5%) stated that they had asthma and 4·6% reported CBE. Besides smoking, which was a risk for both asthma and CBE, there were different risk patterns for self-reported asthma and CBE. In the economically active population there was a tendency that CBE was more common among ‘unskilled and semi-skilled workers’. This fact was further emphasized when the population was merged into the two groups ‘low social position’ and ‘middle/high social position’, with ‘low social position’ as a risk for CBE (OR=1·35, 95% CI=1·06–1·72). No social risk factors were identified for asthma. Living close to heavy traffic was a risk factor for asthma (OR=1·29, 95% CI=1·02–1·62) but not for CBE. Apart from this no living environmental risk factors for obstructive pulmonary diseases were identified. Asthma symptoms and long-standing cough were more common among those subjects living close to heavy traffic compared to those not living close to heavy traffic. To conclude, low social position was a risk factor for CBE and living close to heavy traffic was a risk factor for asthma.