Taiwan Children Health Study

The Taiwan Children Health Study (TCHS) has a multipurpose nationwide design, and is focused on common environmental factors such as outdoor pollutants and household ETS exposure. Communities in Taiwan were selected with the aim of maximizing the variability and minimizing the correlations of exposures to outdoor pollutants based on historic routine air monitoring data. In communities with pollution patterns of interest, neighborhoods with stable, largely middle-income populations were identified from 2004 census data.
To address community-level sources of variability, we randomly sought participating communities within existing financial constraints. School district representatives in participating communities were consulted to identify suitable schools, based on demographic stability, likely parental cooperation, and absence of local pollution sources. Our study population finally comprised middleschool children from 14 diverse communities in Taiwan. To permit cross-sectional assessment of environmental factors, we recruited 350-450 participants from each of the study communities. In each classroom targeted for participation, every student was invited to volunteer.
Classroom-level incentives were used to encourage participation. In each school, science, health, or physical education classes were targeted, excluding any special classes for gifted or learning-disabled subjects. The study protocol was approved by the Institutional Review Board at our university hospital, and it complied with the principles outlined in the Helsinki Declaration [28]. Questionnaire of respiratory health A total of 5,804 seventh and eighth-grade children were recruited from public schools in 14 Taiwanese communities in 2007.
The questionnaire was distributed in all communities simultaneously; subjects were given the forms by project staff following their pulmonary function tests and asked to complete and return them the following day. Questionnaire responses by parents or guardians were used to categorize children’s asthma status, age at asthma diagnosis, wheeze, and history of bronchitic symptoms. Children were considered to have asthma if there was a positive answer to the question “Has a doctor ever diagnosed this child as having asthma?” Active asthma was defined as physician-diagnosed asthma with any asthma-related symptoms or illness in the previous 12 months. Serious asthma was defined as ever visit emergency rooms or ever hospitalized. Early-onset asthma was defined as age of onset for asthma before 5 years of age. Late-onset asthma was onset after 5 years of age. Wheeze was defined as any occurrence of the child’s chest sounding wheezy or whistling.
Current wheeze was defined as wheezing for 3 or more days out of the week for a month or longer in the previous year. Bronchitis status was positive if subjects had a physician-diagnosed episode in the prior 12 months. Chronic cough was defined as cough in the morning or at other times of the day that lasted for three months in a row or more during the prior 12 months. Chronic phlegm was defined by a “yes” answer to the question “Other than with colds, does this child usually seem congested in the chest or bring up phlegm?”