Objective: To evaluate the importance of economic and educational factors in determining the risk of asthma in adults.
Study design and methods: This was a cross-sectional study in a representative sample of Portuguese adults (20,977 females and 18,663 males) from the main regions of mainland Portugal. Participants were categorized according to years of education (< or = 4, 5-9, 10-12 and >12 years) and income (< or = 314, 315-547, 548-815 and >815Euros/month). Information on asthma was based on answers to the following question: 'Have you had asthma in the previous year?' Logistic regression models were fitted to estimate the magnitude of the association between asthma and education/income, adjusting for confounders (body mass index, age, smoking habits, physical activity, area of residence, number of household members and income/education).
Results: In females and males, the odds of having asthma decreased with increasing income (P-value for trend <0.001), with odds ratios of 0.52 [95% confidence intervals (CI) 0.41-0.66] and 0.55 (95%CI 0.44-0.68) for those with a monthly income >815 Euros compared with those with a monthly income 314 Euros, respectively. For both genders, the odds of having asthma were not significantly associated with years of education.
Conclusion: A significant positive association between per capita national income and asthma reinforces that public policy should stress the importance of economic growth as a means for preventing asthma occurrence and improving quality of life.