2. Materials and methods
2.1. Study population
Changchun and Yanji city of Jilin province (China) are selected as the
research cities. Two primary schools are randomly selected from each
city. The study population consisted of students from grade third to
fifth enrolled in the four schools in October 2016, at least 200
students are selected for each grade, and the sampling method is cluster
random sampling. We assess the impact of environmental factors on
respiratory health in children (n =2419).
2.2. Exposure assessment
The environmental impact factors were assessed through the parental
Questionnaire. Whether there is a stinky ditch, garbage station, heating
company or noise in 100 meters around home; The distance from home to
main traffic road; Whether decorated house within three years; Whether
bought furniture within a year; Window opening in winter; Passive
smoking (smoke inhaled every day for more than 15 minutes); Main heating
mode; Main fuel for cooking; The presence or absence of pets; The use of
fume exhauster, insecticide, anophelifuge, moth repellant, air
freshener, disinfectant, and air cleaner were queried.
2.3. Health outcome assessment
Children’s health outcomes included recurrent respiratory tract
infection, pneumonia, asthma, tracheitis/ bronchitis and rhinallergosis,
also ascertained by the parental questionnaire. All diseases are
clinically confirmed and have a clear diagnosis report. A subset of the
study population underwent analysis of pulmonary function at designated
hospital or medical examination center after children’s weight and
standing height were obtained(n = 627). The contents of pulmonary
function analysis included forced vital capacity(FVC), forced expiratory
volume in 1 second (FEV1), peak expiratory flow velocity
(PEF), forced expiratory flow at 25%FVC (V25) and
forced expiratory flow at 75%FVC(V75).
2.4. Ethical Standards
The Ethics Committee of Jilin Provincial Center for Disease Control and
Prevention approved this study. Written informed consent was obtained
from each participant signed by their parents.
2.5. Quality Control
All investigators were trained before the investigation. In the survey,
a questionnaire was set up to verify the questionable questionnaire on
the day. If necessary, a reinvestigation was needed to correct the
mistakes and leak out the vacancy. The data were parallel double entered
and corrected according to the consistency test report. The measurement
instruments used were calibrated according to the same standard.
2.6. Statistical analysis
The database was established by EPIDATA 3.1, and statistical analysis
was carried out by SPSS 17.0 statistical software. The categorical
variables were described as numbers and frequency and the continuous
variables were described as \(\overset{\overline{}}{x}\ \)± s (mean ±
standard deviation). The χ2 test and t-test and were
adopted on comparison between two groups. The least significant
difference (LSD) procedure and the One-Way ANOVA were used to compare
the means of three groups. To Analyze the environmental impact factors
of respiratory diseases, we use multivariate logistics regression
analysis. A P -value < 0.05 (two-tailed) was considered
to be statistically significant.