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The prevalence of asthma increased worldwide until the 1990s, but since then there has been no clear temporal pattern. The present study aimed to assess time trends in the prevalence of current asthma, asthma-like symptoms and allergic rhinitis in Italian adults from 1990 to 2010. The same screening questionnaire was administered by mail or phone to random samples of the general population (age 20-44 yrs) in Italy, in the frame of three multicentre studies: the European Community Respiratory Health Survey (ECRHS) (1991-1993; n = 6,031); the Italian Study on Asthma in Young Adults (ISAYA) (1998-2000; n = 18,873); and the Gene Environment Interactions in Respiratory Diseases (GEIRD) study (2007-2010; n = 10,494). Time trends in prevalence were estimated using Poisson regression models in the centres that repeated the survey at different points in time. From 1991 to 2010, the median prevalence of current asthma, wheezing and allergic rhinitis increased from 4.1% to 6.6%, from 10.1% to 13.9% and from 16.8% to 25.8%, respectively. The prevalence of current asthma was stable during the 1990s and increased (relative risk 1.38, 95% CI 1.19-1.59) from 1998-2000 to 2007-2010, mainly in subjects who did not report allergic rhinitis. The prevalence of allergic rhinitis has increased continuously since 1991. The asthma epidemic is not over in Italy. During the past 20 yrs, asthma prevalence has increased by 38%, in parallel with a similar increase in asthma-like symptoms and allergic rhinitis.

In the early 1990s a multicentre survey on asthma was performed on the young adult population (European Community Respiratory Health Survey - ECRHS). This study is to be repeated in order to estimate changes in the prevalence of asthma-like symptoms during the last decade and to assess the social and economic costs of the disease and their variations among countries. The self-administered questionnaire devised for this purpose is a two-page questionnaire. The first page contains the same items as those used in the first survey with four additional questions related to: 1) the frequency and severity of asthma attacks; 2) the presence of chronic bronchitis; 3) smoking habits; and 4) a visual analogue scale assessing perception of outdoor pollution. The second page aims to collect information regarding the direct and indirect costs of asthma. The influence of the length of the questionnaire on the response rate was assessed in a pilot study in Italy. Two random samples of 150 subjects received either the one-page questionnaire (first page) or the two-page questionnaire. The response rate was compared with that obtained from the first postal wave in the 1991-1992 survey. Although the response rate was unchanged when using the one-page questionnaire (45% versus 45%), it decreased by 7% when the two-page questionnaire was used (38% versus 45%). On the basis of these results, no problem should arise if four more questions are added to the one-page questionnaire. The slight reduction in the response rate of the two-page questionnaire is worrying but could be corrected by the use of telephone interviews.