High prevalence of asthma symptoms in the Canary Islands: climatic influence?

The worldwide variation in asthma prevalence prompted us to carry out a study to assess the variability of asthma-related symptoms in young adults on the islands of Gran Canaria and Tenerife. We used the questionnaire used in the European Community Respiratory Health Survey with the addition of two questions on smoking and ancestors from the Canary Islands. In each island, this questionnaire was distributed to a random sample of 5000 subjects aged 20-44 years. Of the 10,000 subjects, 9,506 (95.06%) were considered eligible. We obtained 7,132 (75.03%) responses. The prevalence of the different symptoms was wheezing 25.3%, nocturnal thoracic tightness 18.0%, awakened by an attack of shortness of breath 13.1%, attack of nocturnal coughing 33.3%, attack of asthma 4.3%, current asthma treatment 6.2%, and nasal allergies 18.0%. Women and smokers showed a significantly higher prevalence of asthma symptoms. No significant difference in symptoms was found between subjects whose ancestors were of Canarian origin and those with ancestors born outside the Canaries. As has been observed on other islands (Great Britain and New Zealand), asthma is common in individuals from 20 to 44 years of age in the Canaries. We hypothesize that climatic conditions play an important role in the prevalence of asthma symptoms.