Background: Remarkable overlap exists in symptoms between asthma and chronic obstructive pulmonary disease (COPD), and the symptoms of the patients with mild asthma are often falsely thought to be caused by smoking. The objective of the study was to determine the prevalence of doctor-diagnosed asthma, asthmatic symptoms and doctor-diagnosed COPD in an adult population. The prevalence and relation to asthma of aspirin intolerance, nasal polyposis, allergic rhinitis and smoking habits were also examined.
Methods: Postal questionnaire survey of a population-based random sample (4300) of adult women and men aged 18-65 years served by the Päijät-Häme Central Hospital in southern Finland (a region with 208 000 inhabitants) was performed.
Results: The non-response-adjusted prevalence (Drane's linear method) of doctor-diagnosed asthma was 4.4% (95% CI: 3.3-5.5%) and of COPD 3.7% (95% CI: 2.7-4.8%). The prevalence of allergic rhinitis was 37.3% (95% CI: 33.3-41.2%), and of overall aspirin intolerance 5.7% (95% CI: 4.4-7.1%). The observed prevalence of aspirin intolerance causing shortness of breath or attacks of asthma was 1.2% and it was higher in patients with doctor-diagnosed asthma than without (8.8% versus 0.8%, relative risk [RR] = 11.4, P < 0.0001), and higher in those with allergic-like rhinitis than without (2.6% versus 0.3%, RR = 7.7, P < 0.0001). The prevalence of nasal polyposis was 4.3% (95% CI : 2.8-5.8%).
Conclusions: The current prevalence of doctor-diagnosed asthma among adults is 4.4%, and allergic rhinitis, nasal polyposis and aspirin intolerance are associated with an increased risk of asthma. There is also association between aspirin-induced asthma and allergic-like rhinitis.