Original article Rising trend of asthma prevalence among Turkish schoolchildren (ISAAC phases I and III) Asthma is a common chronic illness in childhood. In many studies, an increase in asthma prevalence has been reported (1–9), but in a few studies the prevalence was unchanged (10) or decreased (11). This discrepancy may be due to the use of a different methodology (12), diagnostic changes (classification bias) (9, 12), and/or increased awareness of symptoms and the willingness of doctors to diagnose asthma (information bias) (12, 13). Other factors affecting asthma prevalence may be increased awareness of asthma in the community (11), changes in diagnostic methods, and the use of health services for childhood asthma (14). The aims of the International Study of Asthma and Allergies in Childhood (ISAAC) phase I were to describe the prevalence and severity of the symptoms of asthma and other allergic diseases in children living in different geographic centers; make comparisons within and between countries; obtain baseline measures for the assessment of future prevalence trends; provide a framework for future etiologic research into the causation of these diseases (15, 16). ISAAC phase III was used to examine time trends in the prevalence of asthma and other allergic diseases in centers and countries that participated in ISAAC phase I. The time period between ISAAC phase I and phase III data collection must be at least 5 years (17). Our study was conducted on 6- to 12-year-old school- children in Istanbul in 1995 using the ISAAC question- naire. The lifetime prevalence of asthma and wheeze was found to be 9.8% and 15.1% respectively (18). In this study, an atopic family history, food allergy, eczema, and frequent otitis media and sinusitis attacks were found to be important risk factors in asthma prevalence (18). To determine whether the prevalence of childhood asthma is changing in 6- to 12-year-old schoolchildren attending the same primary school, we compared the results from cross- sectional surveys held in 1995 and 2004 using the ISAAC questionnaire. Thus, this study is complementary to the previous report, and the second of a cross-sectional epidemiological survey in children. Background: Asthma is a common chronic illness in childhood. The aim of the study was to examine time trends in the prevalence of asthma using the ISAAC questionnaire in 6- to 12-year-old schoolchildren in Istanbul and factors affecting asthma prevalence. Methods: Two cross-sectional surveys were performed, 9 years apart (1995 and 2004) using the ISAAC protocol. The survey conducted in 1995 was repeated in 2004 using the same questionnaire in the same age group, in the same schools in the same season. The 2500 questionnaires were distributed to the children to be completed by their parents at home. Results: A total of 2387 children (response rate 95.5%) in the 2004 study and 2216 children (response rate 94.3%) in 1995 were included in the final analysis. The overall lifetime prevalence of wheeze increased from 15.1% to 25.3%; prevalence odds ratio (POR) ¼ 1.91, 95% confidence interval (95% CI) ¼ 1.64– 2.21, and P < 0.001. The overall 12-month prevalence of wheeze increased from 8.2% to 11.3%; POR ¼ 1.43, 95% CI ¼ 1.18–1.75, and P < 0.001. The pre- valence of asthma increased significantly from 9.8% to 17.8%; POR ¼ 1.99, 95% CI ¼ 1.67–2.36, and P < 0.001. In both 1995 and 2004, family history of asthma, eczema diagnosed by a physician, food allergy diagnosed by a physician, frequent otitis, frequent sinusitis were associated significantly with high risk for asthma. Conclusions: In the 9-year period from 1995 to 2004, the prevalence of asthma symptoms has increased in 6- to 12-year-old schoolchildren in Istanbul. Risk factors affecting asthma prevalence remained unchanged during the 9-year period. U. Ones 1 , A. Akcay 2 , Z. Tamay 1 , N. Guler 1 , M. Zencir 3 1 Department of Pediatrics, Division of Allergy and Chest Diseases, Istanbul School of Medicine, Istanbul University, Istanbul; 2 Department of Pediatrics; 3 Department of Public Health, Pamukkale School of Medicine, Pamukkale University, Pamukkale, Turkey Key words: asthma; cross-sectional study; ISAAC; prevalence; trends. Ahmet Akcay Department of Pediatrics Istanbul Medical Faculty Capa 34390 Istanbul Turkey Accepted for publication 23 March 2006 Allergy 2006: 61: 1448–1453 Ó 2006 The Authors Journal compilation Ó 2006 Blackwell Munksgaard DOI: 10.1111/j.1398-9995.2006.01145.x 1448