Catherine C. Murphy

Reported biomedical causes and associated medical conditions for mental retardation among 10-year-old children, metropolitan Atlanta, 1985 to 1987

This report describes biomedical causes of mental retardation(MR) among school‐age children and associated medical conditions in children for whom no cause was reported. This study involved 715,10‐year‐old children with MR (intelligence quotient [IQ] 70 or less) born between 1975 and 1977. We determined biomedical causes of MR using a hierarchical approach based on the timing of the event (i.e. prenatal, perinatal, or postneonatal). Among, children with no identified biomedical cause the occurrence of associated medical conditions was examined. No reported biomedical cause could be found in 78% of children with MR (87% mild, IQ 50 to 70; 57% severe, IQ<50). Prenatal causes were present in 12%, perinatal causes in 6%, and postneonatal causes in 4%. On the basis of these findings it was concluded that intensive use of public health prevention strategies can reduce the number of children who receive a diagnosis of MR.

Prevalence of Epilepsy and Epileptic Seizures in 10‐Year‐Old Children: Results from the Metropolitan Atlanta Developmental Disabilities Study

Summary: With reported prevalence rates of 4–9 cases per 1,000 children, childhood epilepsy is a major public health concern. Reported prevalence rates vary, mainly because researchers often use different epilepsy definitions. In addition, total prevalence may be underestimated if incomplete case‐ascertainment methods are used. We used a multiple‐source case‐ascertainment method that included obtaining information from electro‐encephalogram laboratories to estimate the prevalence of epilepsy and to classify seizure types among 10–year‐old children. In the metropolitan Atlanta (GA, U.S.A.) area, we found a lifetime prevalence of childhood epilepsy of 6 per 1,000 (95% confidence interval, 5. 5–6. 5) 10‐year‐old children. However, using capture‐recapture analysis, this prevalence may be as high as 7. 7 per 1,000. Proportionately more boys than girls had epilepsy. The prevalence did not vary appreciably by race. Partial seizures, including secondarily generalized seizures, were the most common seizure type (58%). Of children with epilepsy, 35% had another developmental disability (mental retardation, cerebral palsy, visual impairment, or hearing impairment). An accurate estimate of the public health burden of childhood epilepsy and determination of possible risk factors for idiopathic epilepsy both depend on conducting complete community‐based case ascertainment and obtaining detailed clinical data.

Prevalence of cerebral palsy among ten-year-old children in metropolitan Atlanta, 1985 through 1987

The Metropolitan Atlanta Developmental Disabilities Study was a population-based study (1985 through 1987) to determine the prevalence of five developmental disabilities among 10-year-old children. The disabilities included cerebral palsy, mental retardation, visual impairment, hearing impairment, and epilepsy. The prevalence of cerebral palsy (CP) and a description of the children with CP are reported here. Using a record review approach, we identified 204 10-year-old children with CP (resulting in a prevalence of 2.3 per 1000). The rate of CP was significantly higher among boys (prevalence odds ratio = 1.5; 95% confidence interval = 1.1, 2.0), and the rate was also higher among black children than white children (prevalence odds ratio = 1.3; 95% confidence interval = 1.0, 1.7). Thirty-three of the children (16%) acquired CP postnatally; these children were more likely to be black or male. The gender and racial differences found for acquired CP were greater than those for congenital CP. Approximately 75% of the children had one of the other four disabilities studied; 65% of the children were mentally retarded, 46% had epilepsy, and 15% had a sensory impairment. Our multiple-source method of identifying children with CP gave us a population-based sample from which to determine the prevalence of the condition and to study factors that are associated with CP.

THE DESCRIPTIVE EPIDEMIOLOGY OF INFANTILE SPASMS AMONG ATLANTA CHILDREN

Summary: Purpose: To determine the population‐based epidemiology of infantile spasms (IS) among Atlanta children.

Prevalence and Descriptive Epidemiology of Lennox‐Gastaut Syndrome Among Atlanta Children

Summary: Purpose: To determine the prevalence and descriptive epidemiology of Lennox‐Gastaut Syndrome (LGS) among metropolitan Atlanta children.

Variation in the influence of selected sociodemographic risk factors for mental retardation.

OBJECTIVES This study explored the utility of subdividing mental retardation into groups based on the presence of other neurological conditions. METHODS Data were abstracted from birth certificates as part of a case-control study of mental retardation among 10-year-old children. The study sample included 458 case children and 563 control children selected from public schools. Case children were subdivided on the basis of intelligence quotient (IQ) score and the presence of other neurological conditions. RESULTS Other neurological conditions were more common with severe mental retardation than with mild mental retardation. Regardless of IQ level or the presence of other neurological conditions, boys were more likely than girls to have mental retardation. Older mothers were more likely than younger mothers to have a child with mental retardation accompanied by another neurological condition. High birth order, Black race, and low maternal education were associated with a higher prevalence of isolated mental retardation. CONCLUSIONS These findings suggest that sociodemographic risk factors for mental retardation vary according to the presence of other neurological conditions and that subdivisions based on medical or physical criteria may be useful in epidemiologic studies of mental retardation.

The administrative prevalence of mental retardation in 10-year-old children in metropolitan Atlanta, 1985 through 1987.

OBJECTIVES In this study, data from the Metropolitan Atlanta Developmental Disabilities Study were used to determine the administrative prevalence (i.e., the number of children previously identified for service provision) of mental retardation among 10-year-old children during the years 1985 through 1987. METHODS Children with mental retardation (intelligence quotient [IQ] of 70 or lower) were identified by review of records from multiple sources, with the public schools as the primary source. RESULTS The overall administrative prevalence of mental retardation was 12.0 per 1000 children. The rate for mild mental retardation (IQ of 50 to 70) was 8.4 per 1000 and the rate for severe mental retardation (IQ lower than 50) was 3.6 per 1000. The prevalence was higher in Black children than in White children (prevalence odds ratio [POR] = 2.7) and in boys than in girls (POR = 1.4). Children with severe mental retardation had more coexisting disabilities than did children with mild mental retardation. CONCLUSIONS The mental retardation prevalence rates reported here, especially the race-specific rates, may reflect social and demographic features unique to the metropolitan Atlanta area and therefore should be used with caution in making comparisons with other populations.

Mild mental retardation in black and white children in metropolitan Atlanta: a case-control study.

OBJECTIVES This study assessed differences in the prevalence of mild mental retardation, defined as an intelligence quotient (IQ) from 50 to 70, between Black and White children. METHODS A case-control study design was used. Ten-year-old children with mental retardation were identified from multiple sources. Information on race, sex, maternal age, birth order, economic status, and maternal education was abstracted from birth certificates of 330 case children and 563 control children (public school students). RESULTS The crude Black-White odds ratio (OR) was 2.6, but it was reduced to 1.8 after the other five covariates were controlled. The disparity was largest among children whose mental retardation was first diagnosed when they were 8 to 10 years old (adjusted OR = 2.5). We found no significant difference in the occurrence of mild mental retardation between Black and White children diagnosed before the age of 6 years (adjusted OR = 1.2). Black children had a higher prevalence of mild mental retardation within all strata of the other five covariates. CONCLUSIONS Five sociodemographic factors accounted for approximately half of the excess prevalence of mild mental retardation among Black children. Possible reasons for the residual difference are discussed.

Hearing impairment among 10-year-old children: metropolitan Atlanta, 1985 through 1987.

The prevalence of hearing impairment among 10-year-old children in metropolitan Atlanta between 1985 and 1987 was evaluated. Hearing-impaired children were identified by reviewing records at public schools and health and social service agencies. The prevalence was 1.1 per 1000 and was slightly higher among Blacks and boys than among Whites and girls. The most common known causes of hearing impairment were meningitis (0.3 per 1000), genetic and hereditary conditions (0.2 per 1000), and congenital rubella syndrome (0.1 per 1000). For 55% of the children, the etiology of the hearing loss could not be determined. Most (74%) of the children were diagnosed after the age of 2, suggesting that methods of early identification need to be improved.

Legal blindness among 10-year-old children in Metropolitan Atlanta: prevalence, 1985 to 1987.

The prevalence of legal blindness in 10-year-olds in metropolitan Atlanta was 6.8 per 10,000 during 1985 to 1987. The prevalence was 8.8 per 10,000 in Black boys, 8.6 per 10,000 in White boys, 6.7 per 10,000 in White girls, and 1.8 per 10,000 in Black girls. Retinopathy of prematurity was the most common known cause (1.0 per 10,000). Of the 61 cases, 40 had other disabilities, including 14 with mental retardation, cerebral palsy, and epilepsy. The low prevalence among Black girls and the frequent occurrence of blindness with other disabilities are noteworthy.