Journal of Rehabilitation Medicine 51-1CompleteIssue | Page 51

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J. Yuan et al.
resided in a given household, all the children in that household
were recruited.
Screening and diagnosis
All children under 7 years of age in the selected areas were asked
to undergo screening at a local hospital with paediatric physici-
ans or neurologists who had received specialized training. The
screening was in 2 phases: enquiry about medical history and
motor development history to gather information about motor
development delay; and physical examination to determine
whether there were abnormal movement, posture, reflex, muscle
tension and muscle strength and whether motor development
was normal. In order to be cautious and comprehensive, if either
motor development delay or physical examination was positive,
the screen was regarded as positive. Children who screened
positive were asked to undergo diagnosis 10 days later with
another senior paediatric physician or neurologist. They were
examined and referred for further examination, such as magnetic
resonance imaging (MRI) of the head, electromyography, etc.,
as appropriate. Potential cases of CP, or subjects who could not
be diagnosed or excluded, were referred to senior paediatric
neurologists or rehabilitation specialists in the local hospitals.
CP diagnostic criteria: (i) persistent central movement disorder;
(ii) abnormal movement, posture and reflex; (iii) abnormal mus-
cle tension and muscle strength; (iv) the symptom was caused
by non-progressive brain damage sustained as a foetus or infant.
CP exclusion criteria: (i) transient development delay; (ii)
hereditary metabolic disease with motor dysfunction, such
as metachromatic leukodystrophy, dopa-responsive dystonia,
Duchenne muscular dystrophy, or myotonic muscle dystrophy;
(iii) presumed insult to the brain, specific and occurring after
birth (e.g. an intracranial haemorrhage caused by late-onset
vitamin K or craniocerebral trauma).
Matched control group: All children in the control group were
recruited from the same areas during the same screening period
(from September 2011 to September 2012). Each child with CP
was matched with 4 typically developing controls, according
to location (community or town), age (± 3 months), and sex.
Data collection
Data collection was undertaken between September 2011
and September 2012. Caregivers and paediatric rehabilitation
practitioners were requested to jointly complete the risk factor
questionnaire. Items in the questionnaire pertaining to potential
risk were devised by a Delphi procedure. Firstly, 20 renowned
paediatric rehabilitation experts were asked to list the risk
factors for CP and to classify the risk factors according to their
clinical experience via e-mail. Based on the results, a prelimi-
nary questionnaire was constructed, which was then returned
to the 20 experts for further advice. Analysis, statistical treat-
ment, and modification of the questionnaire were carried out,
and minor events were elaborated further. The questionnaires
included 3 concepts: (i) maternal, prenatal and gestational risk
factors; (ii) perinatal risk factors; and (iii) postnatal risk factors/
neonatal diseases. Questions included parental age at concep-
tion, educational level of parents, mean household income,
location of residence, contact history of parents with physical
and chemical agents, moving into a freshly painted room for
6 months or more during pregnancy, family history of genetic
diseases, maternal concomitant diseases during pregnancy,
maternal medication history, the nutritionl status of the mother,
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frequency of ultrasound scanning during pregnancy, whether
an X-ray examination or computed tomography (CT) scan was
performed, maternal alcohol consumption during pregnancy,
maternal active or passive smoking during pregnancy, precon-
ception irregularity of menstrual cycle, gravidity and parity,
abortion times, foetal times, history of abnormal pregnancy, and
vaginal bleeding during pregnancy; (ii) perinatal risk factors,
including completed weeks of gestation, mode of delivery,
dystocia, abnormalities in progression of labour, birth asphyxia
(based on medical record at birth),and birthweight; and (iii)
postnatal risk factors/neonatal diseases, including neonatal
hypoxic–ischaemic encephalopathy (HIE), neonatal seizures,
infection, and jaundice.
Birth-weight was classified into 3 groups: <2,500, 2,500–
4,000 and > 4,000  g. Gestational age was classified into 3
groups: < 37, 37~42 and ≥ 42 weeks. Pregnancies were clas-
sified as singleton or multiple. Parental age was classified into
3 groups: ≤ 25, 25–30 and ≥ 30  years. Educational level of
parents was classified into 5 groups: illiteracy or elementary
school, junior middle-school, senior middle-school, univer-
sity, and post-graduation or higher education. Residence type
was classified as urban or rural. Gravidity was classifed into
3 groups: First gravidity for the current birth, the second
time, and multigravidity (≥ 3 times); parity was classifed into 3
groups: primiparity for the current birth, the second time, and
multiparity (≥ 3 times).The latter result was consistent with
the grouping. Household income per capita was classified as
<10,000 and ≥ 10,000 Chinese yuan. History of contact with
physical and chemical agents was defined as > 6 months contact
history with pesticides such as propoxur (aryl carbamate), di-
methoate (dithiophosphoric acid, o-dimethyl-s ester), decorative
materials such as emulsion paint (e.g.polyvinyl acetate latex
paint) and glue (e.g. plywood), benzene (C6H6), mercury, arse-
nic and chemical solvents (e.g.methanol ), all these explore time
was more than 4 days per week, and 7 hours per day). History
of contact with X-rays was defined as ≥ 3 times or more. Active
or passive maternal smoking status was classified into 3 groups:
0, 1–2 and ≥ 3 cigarettes per day. Mode of delivery was divi-
ding into vaginal delivery or caesarean section. Abortion data
were classified into 3 groups: 0, 1 and ≥ 2 abortions. Data were
independently entered into Epidata Entry version 3.2 (EpiData
Association, Odense, Denmark) by 2 separate investigators.
Medical records were consulted when necessary, if available.
Statistical analyses
Statistical analyses were conducted using Stata (version 12.0;
STATA Corp., College Station, TX, USA). Conditional logistic
univariate and multivariate regression analyses were performed
to detect potential risk factors. For the univariate logistic regres-
sion analyses, alpha was set at p < 0.10. Significant risk factors
were submitted to multivariate regression analysis. Bivariate
odds ratios and 95% confidence intervals (95% CIs) were cal-
culated. Alpha was set at 0.05.
RESULTS
Prevalence
A total of 50,596 children (age range 9–81 months), from
a population of 51,266 eligible children, were included
in the analysis. The other children were not screened
(1.31%). Of the included children, none of the parents or