Introduction
Since 1968, The Centers for Disease Control and Prevention (CDC) has
conducted surveillance of birth defects (i.e., structural malformations
and genetic diseases) in the five-county metropolitan Atlanta area.
However, those birth defects that are evident at birth (e.g., cleft
palate and spina bifida) represent only part of a spectrum of
developmental problems that appear during childhood. Other conditions
(e.g., mental retardation, autism, and cerebral palsy) usually are
manifested after infancy and may be sufficiently severe to require
specialized medical and education services for many years. Such
conditions are referred to as developmental disabilities.
To address the problem of developmental disabilities among children, CDC,
the former Division of Birth Defects and Developmental Disabilities,
which was funded by the
Agency for Toxic Substances and Disease Registry (ATSDR), and the
Georgia Department of Human Resources, initiated the
Metropolitan Atlanta Developmental Disabilities Study (MADDS) in
1984. For this study, which was conducted in Atlanta during 1984-1990,
investigators devised methods for determining the prevalence of mental
retardation, cerebral palsy, legal blindness, hearing loss, and epilepsy
among children 10 years of age. Children who had these conditions were
identified by searching record systems of sources that were likely to
contain information relating to the evaluation or treatment of children
with developmental disabilities (e.g., schools, hospitals, and state
programs for persons who have developmental disabilities). The majority
of the children were identified through special education departments
within the Atlanta area public school systems. The success of this study
prompted CDC to establish the Metropolitan Atlanta Developmental
Disabilities Surveillance Program (MADDSP) in 1991, an ongoing system
for monitoring the occurrence of selected developmental disabilities.
MADDSP is located at CDC in the National Center on Birth Defects and
Developmental Disabilities.
The two principal objectives of MADDSP are to a)
provide regular and systematic monitoring of prevalence rates of
selected developmental disabilities according to various demographic
characteristics of children and their mothers and b) provide a framework
for initiating special studies of children who have the selected
developmental disabilities by establishing a population-based case
series of such children.
Methods
MADDSP was established to ascertain all children who have one or more of
four developmental disabilities -- mental retardation, cerebral palsy,
hearing loss, and vision impairment -- in the five-county (i.e.,
Clayton, Cobb, Dekalb, Fulton, and Gwinnett) metropolitan Atlanta area.
Autism spectrum disorders was added as a fifth disability beginning in
the 1996 study year. In 1996, the study area had a population of 33,309
8-year-olds and 289,456 children 3-10 years of age. This area has an
active birth defects surveillance program -- the Metropolitan Atlanta
Congenital Defects Program, which is operated by CDC. Consequently,
additional medical data can be obtained by linking the children
identified through MADDSP to the birth defects registry.
The ascertainment methodology of MADDSP relies on the consequences of Part
B of Public Law 94-142 "as amended", the Individuals with Disabilities
Education Act (IDEA), which mandates that the public schools provide a
free and appropriate education for all disabled children between the
ages of 3 and 21 years. As a result, most children eligible for MADDSP
are either enrolled in special education programs at nine public school
systems serving the study area or enrolled in other Georgia Department
of Education programs for children who have developmental disabilities
(e.g., state schools for children who are hearing or vision impaired and
regional psychoeducational centers). Additional sources used to identify
children include Georgia Department of Human Resources facilities for
children with a developmental disability, area pediatric hospitals and
the clinics associated with these facilities, comprehensive diagnostic
and evaluation centers for individuals with developmental disabilities,
as well as a number of private physicians and clinicians who provide
diagnostic services for children with developmental disabilities.
Source records (e.g., medical and school records) are reviewed annually
for children who are potentially eligible for inclusion in the
surveillance program.
In the 1991-1994 study years, children aged 3- to 10-years were included
in MADDSP. Starting in the 1996 study year, we began to focus on a
narrower age range in order to make the surveillance program more
timely.
Case definition
For the 2000 study year, a case child in MADDSP is defined as a child:
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Who is 8 years old any time during the study year of interest;
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Whose parent(s) or legal guardian(s) reside in the five-county
metropolitan Atlanta area at some time during the study year of
interest; and
-
Who has one or more of the five developmental disabilities.
Developmental Disabilities
Definitions
Autism Spectrum Disorders
Autism Spectrum Disorders (ASD) are defined as a constellation of
behaviors indicating social, communicative, and behavioral impairment or
abnormalities. The essential features of ASD are (a) impaired reciprocal
social interactions, (b) delayed or unusual communication styles, and
(c) restricted or repetitive behavior patterns.
A child is included as a confirmed case of ASD if he or she displays
behaviors (as described by a qualified professional) consistent with the
Diagnostic and Statistical Manual of Mental Disorders - Fourth Edition
(DSM-IV) diagnostic criteria for Autistic Disorder, Pervasive
Developmental Disorder-Not Otherwise Specified (including Atypical
Autism), or Asperger's Disorder. A qualified professional is defined as
an educational, psychological or medical professional with specialized
training in the observation of children with developmental disabilities
(e.g., special education teacher, clinical / developmental / school
psychologist, speech/language pathologist, learning specialist, social
worker, developmental pediatrician, child psychiatrist, pediatric
neurologist). Behavioral descriptions are reviewed by autism
experts using a coding scheme based on DSM-IV criteria to determine
autism case status.
Cerebral Palsy
Cerebral palsy is defined as a group of non-progressive, but often
changing, motor impairment syndromes secondary to lesions or anomalies
of the brain arising at any time during brain development. Children with
postnatally acquired cerebral palsy are included. The impairment of
motor function may result in paresis, involuntary movement, or
incoordination. It does not include motor disorders that are transient,
that result from progressive disease of the brain, or that are due to
spinal cord abnormalities/injuries.
Children are included as confirmed cases of cerebral palsy if they have
been (a) diagnosed as having cerebral palsy by a qualified physician or
(b) identified by other qualified professionals as having this
disability on the basis of physical findings noted in source records. A
qualified professional is defined as a physician, physical therapist,
occupational therapist, nurse practitioner, or physician's assistant who
specializes in developmental disabilities, neurology, orthopedics or
pediatrics. A determination is made by medical staff of the
Developmental Disabilities Program that the physical findings are
consistent with a diagnosis of cerebral palsy.
Hearing Loss
Hearing loss is defined as a measured, bilateral, pure-tone hearing
loss at frequencies of 500, 1000, and 2000 hertz averaging 40 decibels
(dB) or more, unaided, in the better ear. In the absence of a measured,
bilateral hearing loss, children meet the case definition if their
source records include a description, by a licensed or certified
audiologist or qualified physician, of a hearing loss of 40 dB or more
in the better ear (e.g., profound sensorineural hearing loss). Severity
is defined on the basis of the following hearing loss levels (measured
in the better ear): moderate (a hearing loss of 40-64 dB), severe (a
hearing loss of 65-84 dB), and profound (a hearing loss of >=85 dB).
Mental retardation /Intellectual Disability
Mental retardation is defined as a condition marked by an
intelligence quotient (IQ) of <=70 on the most recently administered
psychometric test. In the absence of an IQ score, a written statement by
a psychometrist that a child's intellectual functioning falls within the
range for mental retardation is acceptable. The severity of mental
retardation is defined according to the following International
Classification of Disease, Ninth Edition, Clinical Modification
(ICD-9-CM) categories: mild (an IQ of 50-70), moderate (an IQ of 35-49),
severe (an IQ of 20-34), and profound (an IQ of <20).
Vision Impairment
Vision impairment is defined as a measured visual acuity of 20/70 or
worse, with correction, in the better eye. In the absence of a measured
visual acuity, a child is considered a case if a source record includes
(a) a functional description, by a qualified physician or vision
professional, of visual acuity of 20/70 or worse (e.g., light perception
only) or (b) a statement by a qualified physician or vision professional
that the child has low vision or blindness. Severity of visual
impairment is defined using the WHO categories low vision (20/70 -
20/400) and blindness (worse than 20/400) or the U.S.A. categories of
low vision (20/70 to better than 20/200) and legal blindness (20/200 or
worse).
Prevalence
Prevalence of selected developmental disabilities among children 8 years
of age, Metropolitan Atlanta Developmental Disabilities Surveillance
Program, 2000 Surveillance Year per 1,000 children:
Publications
National Center on Birth Defects and Developmental Disabilities (NCBDDD)
staff have written scientific papers using information from MADDSP.
These papers look at such topics as how common autism spectrum disorders
are and what causes hearing loss in children. You can see a list
of these papers (starting in 1990) by using the keyword search on the
NCBDDD publications Web page. Choose "MADDSP (Metropolitan Atlanta
Developmental Disabilities Surveillance Program)" in the keyword box on
the search page. You can choose whether you want the list to be
sorted by author or by date. You can also choose to have the list
appear with or without graphics. Click on the Submit button.
You will see a list of papers that have information from MADDSP.
The list will include the complete reference for each paper and a link
to an abstract of the paper or to the full text, when available. [Go
to NCBDDD publications keyword search page]
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Date: October 29, 2004
Content source: National Center on Birth Defects and Developmental
Disabilities
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