[Third nationwide survey of childhood asthma in urban areas of China].

OBJECTIVE Asthma is the most common chronic respiratory disease among children. In recent years, the prevalence of childhood asthma was rising in most countries around the world. This nationwide study was conducted to investigate the prevalence of childhood asthma in urban areas of large cities in China, and to find the characteristics of attacks, the diagnosis and treatment status, and provide scientific data for improving the prevention and management of asthma in children. METHOD This nationalwide, cross-sectional survey was organized by the National Cooperative Group on Childhood Asthma, and conducted in 43 cities all over the country, including 27 capital cities of provinces or autonomous regions, 4 municipalities, from September 2009 to August 2010. Children born from July 1st 1995 to June 30th 2010 were enrolled in the survey, consisting of children who had been living in the surveyed cities and those born outside the city but had lived in the cities for over 6 months. Schools, kindergartens and communities in each city were selected by phased stratified random cluster sampling. Standardized preliminary questionnaire was used for screening out possible patients in the survey. Diagnosis of asthma was confirmed by enquiry of history, together with review of previous record and tests, physical examination in suspected asthmatic children. Asthmatic children were further asked for past diagnosis, treatment and concomitant allergic diseases. Double entry and validation was adopted for all data using Epi-Info software, and analysis was carried out by SPSS V19.0. RESULT Totally 463 982 children were investigated for the survey. Asthma was diagnosed in 13 992 children, 12 634 children with classical asthma (90.3%) and 1358 children with cough variant asthma (9.7%); 4387 cases (31.4%) were newly diagnosed in all asthmatic children. The total asthma incidence rate was 3.02% (95%CI:2.97%-3.06%), with classical asthma at 2.72% (95%CI:2.68%-2.77%) and cough variant asthma at 0.29% (95%CI:0.28%-0.31%). The prevalence in last two-year (2009-2010) was 2.32% (95%CI:2.28%-2.37%). The prevalence of asthma in male and female children was 3.51% (8495/241 811) and 2.29% (5089/222 160) respectively with significant difference (χ(2) = 608.7, P < 0.01). Preschool children (3-5 years old) had the highest prevalence of asthma (4.15%), which was significantly higher than that of school-age children (6-14 years old, 2.82%) and infants (0-2 years old, 1.77%). In different regions of the country, the highest rate was found in East China (4.23%), and the lowest rate in North-east China (2.00%). Among different cities, highest rate was found in Shanghai (7.57%) and the lowest rate in Lasa (0.48%). Family allergic history was reported in 45.2% (n = 6321) , personal history of allergy reported in 72.5% (n = 10 143) , and allergic rhinitis reported in 50.1% (n = 7010) asthmatic children. Respiratory tract infection (87.9%, n = 12 299) and changes of weather condition/inhaling cold air (51.5%, n = 7204) were the most common triggers of asthma exacerbation. The common clinical manifestations of asthma were cough (91.3%, n = 12 771) and wheezing (76.2%, n = 10 659). Dysphasia (3.1%, n = 438), orthopnea (6.5%, n = 905), cyanosis (3.8%, n = 528) or sweating (5.0%, n = 696) was relatively less often seen during exacerbation. In last year, more than half (61.4%, 4826/12 518) of the patients experienced asthma attack, 32.1% (4028/12 530) went to emergency room once, and 16.3% (2039/12 514) were hospitalized for treatment. Bronchodilators were used in 71.4% (n = 9986), inhaled corticosteroid in 58.7% (n = 8209), antibiotics in 75.1% (n = 10 504) of asthmatic children. Peak flow meter was used in 14.3% (1449/10 145) of asthmatic children 5 years and older for monitoring. CONCLUSION The total asthma incidence of childhood asthma aged 0-14 year old in cities in China was 3.02% and prevalence in last two years was 2.32%. The asthma prevalence was significantly different among regions, cities, ages, and genders. Nearly one third of patients with asthma was not diagnosed in early stage or diagnosed correctly. The treatment and management of asthma in children awaits improvement as well.