Prevalence and risk factors for asthma among children aged 0-14 years in Hangzhou: a cross-sectional survey.BACKGROUND
 Prevalence varies among different countries and cities.  We aimed to obtain the prevalence, describe the characteristics, and discover factors that may relate to asthma in Hangzhou.


 This cross-sectional study was conducted in Hangzhou.  The subjects were children aged 14 years and younger.  A control group of non-asthma children that matched in age and sex with each asthmatic patient was also randomly selected and interviewed.  International Study of Asthma and Allergies in Childhood and National Epidemiology study of Asthma and Allergies in China questionnaires were used in this survey.


 We have questionnaired 13,877 children, and 665 (4.8 %) children were diagnosed asthma.  The guardians regarded the cost of asthma management affordable in 49.4 %, tolerable in 46.9 %, and intolerable in 3.7 %.  Both guardians and children have been absent from work or school due to children's asthma.  Respiratory tract infection was the most common trigger of asthma attacks (85.1 %).  Other common causes included cold air, house dust, exercise, fish and shrimp, pollen, and et al.  Interestingly, we also found in children 6 years and older, some triggers happened more than that in children 5 years and younger.  Those factors included exercise, emotional changes, house dust, pollen, renovation works in the home, mosquito-repellent incense and pets (all the p values were <0.05).  We compared some factors may relate to asthma development.  Higher percentage of family history of asthma, personal history of allergy (atopic dermatitis, drug allergy and food allergy), comorbidities (allergic rhinitis, sinusitis, adenoidal hypertrophy, and urticaria), caesarean birth and complications ever happened during pregnancy were discovered in asthma children than in non-asthma children (all the p values were <0.05).  Exclusive breastfeeding within first 6 months and keeping animals had higher percentage in non-asthma children than in asthma (both the p values were <0.05).  Inhaled corticosteroid (ICS)/ICS + long-acting beta2 agonists (LABA) was applied to 46.2 % of patients.  Traditional Chinese medicine (TCM) was used in 44.2 % of asthma children, while leukotriene receptor antagonist (LTRA) was used in 36.4 % of them.  The adherence scored higher in TCM than in ICS/ICS + LABA (P = 0.003) and LTRA.


 CONCLUSIONS
 In conclusion, we conducted an epidemiology study in Hangzhou.  The prevalence of childhood asthma was 4.8 %.  Asthma was an economic and social burden to both children and guardians.  Risk factors of asthma development may include caesarean birth, personal history of allergy and concomitant allergic diseases.  Exclusive breastfeeding within first 6 months and keeping animals might be protecting factors.  TCM was really popular in China besides ICS/ICS + LABA and LTRA.
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