Increased risk for developmental disabilities in children who have major birth defects: a population-based study

OBJECTIVE

We sought to quantify the strength of associations between each of four specific developmental disabilities (DDs) and specific types of major birth defects.

METHODS

We linked data from 2 independent surveillance systems, the Metropolitan Atlanta Congenital Defects Program and the Metropolitan Atlanta Developmental Disabilities Surveillance Program. Children with major birth defects (n = 9142; born 1981-1991 in metro Atlanta) and 3- to 10-year-old children who were born between 1981 and 1991 in metro Atlanta and identified between 1991 and 1994 as having mental retardation, cerebral palsy, hearing impairment, or vision impairment (n = 3685) were studied. Prevalence ratio (PR), which is the prevalence of a DD in children with 1 or more major birth defects divided by the prevalence of the same DD in children without major birth defects, was measured.

RESULTS

Among the 9142 children who were born with a major birth defect, 657 (7.2%) had a serious DD compared with 0.9% in children with no major birth defect, yielding a PR of 8.3 (95% confidence interval: 7.6-9.0). In general, the more severe the DD, the higher was the PR. Birth defects that originated in the nervous system and chromosomal defects resulted in the highest PRs for a subsequent DD. For all other categories of birth defects, PRs were lowest when all major birth defects present were confined to a single category (ie, isolated defects). PRs for any DD increased monotonically with the number of coded birth defects per child or the number of different birth defect categories per child, regardless of the severity of the defect or whether defects of the nervous system, chromosomal defects, or "other syndromes" were counted.

CONCLUSIONS

These data highlight the possible early prenatal origins of some DDs and suggest that both the number of coded birth defects present and the number of anatomic systems involved are strongly related to functional outcomes.

Association of very low birth weight with exposures to environmental sulfur dioxide and total suspended particulates

This paper presents results of a population-based case-control study of the association between maternal exposures to environmental sulfur dioxide and total suspended particulates (TSP) and risk for having a very low birth weight (VLBW) baby, i.e., one weighing less than 1,500 g at birth. The study, which took place between April 1, 1986 and March 30, 1988, comprised 143 mothers of VLBW babies and 202 mothers of babies weighing 2,500 g or more living in Georgia Health Care District 9. Environmental exposure estimates (microg/m3) were obtained through environmental transport modeling that allowed us to assign environmental sulfur dioxide and TSP exposure estimates at the birth home of each study subject. Exposures less than or equal to 9.94 microg/m3, the median of TSP and sulfur dioxide exposures for the controls, were considered as referent exposures. Exposures to atmospheric TSP and sulfur dioxide above the 95th percentile (56.75 microg/m3) yielded an adjusted odds ratio of 2.88 (95% confidence interval (CI): 1.16, 7.13), that from above the 75th to the 95th percentile (25.18-56.75 microg/m3) yielded an adjusted odds ratio of 1.27 (95% CI: 0.68, 2.37), and that from above the median (9.94 microg/m3) to the 75th percentile, an adjusted odds ratio of 0.99 (95% CI: 0.51, 1.72). The trend demonstrated in these adjusted estimates suggests an association between VLBW and maternal exposures to high levels of air pollution.

Relative and attributable risks for moderate to profound bilateral sensorineural hearing impairment associated with lower birth weight in children 3 to 10 years old

OBJECTIVE

To determine the prevalence, relative risks, and attributable fractions for congenital bilateral sensorineural hearing impairment in relation to lower birth weight among children born in the 1980s and living in the metropolitan Atlanta area from 1991 through 1993.

METHODS

We used the population-based, active case ascertainment Metropolitan Atlanta Developmental Disabilities Surveillance Program that conducts surveillance in the five-county metropolitan Atlanta area. Hearing impairment was defined as a bilateral, pure-tone hearing loss at frequencies of 500, 1000, and 2000 Hz averaging 40 dBs or more, unaided, in the better ear. Case children, 3 to 10 years of age, with sensorineural loss of presumed congenital origin were included in these analyses (n = 172). Prevalence rates and relative risks were computed for various birth weight categories by hearing level, sex, race, the presence or absence of coexisting developmental disabilities, and gestational age. Attributable fractions were calculated for low birth weight and very low birth weight children by race.

RESULTS

The overall prevalence rate of presumed congenital bilateral sensorineural hearing impairment was 5.3 cases per 10 000 3-year survivors. The prevalence was 4.1 per 10 000 among children weighing >/=4000 g, 3.7 per 10 000 among those weighing 3000 to 3999 g, 6.6 per 10 000 among those 2500 to 2999 g, 12.7 per 10 000 among those 1500 to 2499 g, and 51.0 per 10 000 among those <1500 g. There was virtually no difference in birth weight-specific rates of hearing impairment across three hearing levels. The presence of coexisting developmental disabilities was associated with a much stronger inverse trend with birth weight. Black children weighing <2500 g had much higher rates of hearing impairment than comparable white children. The overall percentage of moderate to profound congenital bilateral sensorineural hearing loss in the entire study population that was attributable to children weighing <2500 g or <1500 g was estimated to be 18.9% and 9.4%, respectively. Prematurity did not alter the magnitude of risk among children weighing <2500 g.

CONCLUSIONS

The results presented here provide recent estimates of the rates, relative risks, and attributable fractions for congenital bilateral sensorineural hearing impairment by birth weight among children in the United States. The elevated relative risks among children weighing 2500 to 2999 g and 1500 to 2499 g may have implications for future newborn hearing screening criteria.

Alcohol use prior to pregnancy recognition

BACKGROUND

Frequent alcohol use during the first 8 weeks of pregnancy can result in spontaneous abortion and dysmorphologic changes in the developing organ systems of the embryo, including the heart, kidneys, and brain. However, few population-based studies are available that describe the prevalence of frequent drinking (6 or more drinks per week) among women prior to and during early pregnancy (the periconceptional period), and the sociodemographic and behavioral factors that characterize these women. Such knowledge is fundamental to the design of targeted interventions for the prevention of fetal alcohol syndrome (FAS) and other prenatal alcohol-related disorders.

METHODS

This cross-sectional study used survey data collected by the National Center for Health Statistics as part of the 1988 National Maternal and Infant Health Survey (NMIHS). Weighted prevalence estimates were calculated using SUDAAN, and multivariate analyses were used to determine risk factors for frequent drinking.

RESULTS

Forty-five percent of all women surveyed reported consuming alcohol during the 3 months before finding out they were pregnant, and 5% reported consuming 6 or more drinks per week. Sixty percent of women who reported alcohol consumption also reported that they did not learn they were pregnant until after the fourth week of gestation. Risk factors for frequent drinking during the periconceptional period included 1 or more of the following: being unmarried, being a smoker, being white non-Hispanic, being 25 years of age or older, or being college educated.

CONCLUSIONS

Half of all pregnant women in this study drank alcohol during the 3 months preceding pregnancy recognition, with 1 in 20 drinking at moderate to heavy levels. The majority did not know they were pregnant until after the fourth week of pregnancy, and many did not know until after the 6th week. Alcohol is a teratogen capable of producing a number of adverse reproductive and infant outcomes. Public health measures needed to reduce these potentially harmful exposures include alcohol assessment, education, and counseling for women of childbearing age, with referral sources for problem drinking, and family planning services for pregnancy postponement until problem drinking is resolved.

Is maternal age a risk factor for mental retardation among children?

The purpose of this study was to determine whether older or very young maternal age at delivery is associated with mental retardation in children. Ten-year-old children with mental retardation (an intelligence quotient of 70 or less) were identified in 1985-1987 from multiple sources in the metropolitan Atlanta, Georgia, area. These children were subdivided into two case groups according to whether they had concomitant developmental disabilities or birth defects affecting the central nervous system (codevelopmental retardation) or did not have such disabilities (isolated retardation). Control children were randomly chosen from the regular education files of the public school systems in the study area. Data on sociodemographic variables were gathered from birth certificates. Children of teenaged mothers were not at increased risk for either form of retardation and children of mothers aged > or =30 years were not at increased risk for isolated retardation, in comparison with children of mothers aged 20-29 years. A markedly elevated risk of codevelopmental retardation was seen among black children of mothers aged > or =30 years that was not attributable to Down syndrome. A modest increase in risk for codevelopmental retardation was observed among white children born to older mothers, but it was entirely due to Down syndrome.

Prevalence and characteristics of children with serious hearing impairment in metropolitan Atlanta, 1991-1993

OBJECTIVES

There is a paucity of data describing the epidemiology of serious hearing impairment among children in the United States. This report provides information on the prevalence of serious hearing impairment among children born in the 1980s and living in the metropolitan Atlanta area in 1991-1993 and on the characteristics of children with serious hearing impairment.

METHODS

Data for this report are drawn from the Metropolitan Atlanta Developmental Disabilities Surveillance Program, an ongoing, active case-ascertainment system for mental retardation, cerebral palsy, hearing impairment, and vision impairment among children 3 to 10 years of age. Hearing impairment was defined as a bilateral, pure-tone hearing loss at frequencies of 500, 1000, and 2000 Hz averaging 40 decibels or more, unaided, in the better ear. Both severity and type of hearing loss were examined. Cross-sectional as well as birth cohort prevalence rates of serious hearing impairment were computed by sex and by race. The presence of mental retardation, cerebral palsy, vision impairment, or a seizure disorder was also assessed. An attempt was made to determine the probable etiology of a subset of the cases.

RESULTS

The average, annual prevalence rate for moderate to profound hearing loss was 1.1 per 1000. The prevalence rate increased steadily with age. Ninety percent of all cases for which the type of loss was recorded were sensorineural. The highest rate was seen among black male children (1.4 per 1000). Thirty percent of case children had another neurodevelopmental condition, most frequently mental retardation. Black male children also experienced the highest rate of presumed congenital hearing impairment. The mean age at which children with presumed congenital hearing impairment first met the surveillance case definition was 2. 9 years. A probable etiology could only be found for 22% of cases born in the study area.

CONCLUSIONS

The data presented here provide information on the descriptive epidemiology of serious hearing impairment among United States children. The reasons for the higher rates among black children, especially males, may be a fruitful direction for further research.

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.

The relationship between idiopathic mental retardation and maternal smoking during pregnancy

OBJECTIVES

Smoking has been linked to small cognitive, achievement, and behavioral deficits but has not been associated with more severe cognitive impairments. This investigation evaluated the relationship between maternal smoking during pregnancy and idiopathic mental retardation (MR).

METHODS

Data on maternal smoking during pregnancy were obtained during face-to-face interviews with the mothers of 221 children with idiopathic MR and the mothers of 400 children attending public school. All children had been born in the five-county metropolitan Atlanta area in 1975 or 1976 and were living in the area when they were 10 years of age. We used exposure odds ratios (ORs) to assess the relationship between maternal smoking and MR, controlling for sex, maternal age at delivery, race, maternal education, economic status, parity, and alcohol use.

RESULTS

Maternal smoking during pregnancy was associated with slightly more than a 50% increase in the prevalence of idiopathic MR (adjusted OR, 1.6; 95% confidence interval, 1.0-2.4), and children whose mothers smoked at least one pack a day during pregnancy had more than a 75% increase in the occurrence of idiopathic MR (OR, 1.9; 95% confidence interval, 1.0-3.4). This increase was neither accounted for by other sociodemographic risk factors for MR nor explained by an increase in the prevalence of low birth weight among the children of smokers.

CONCLUSIONS

Our data suggest that maternal smoking may be a preventable cause of mental retardation.

Low birthweight and the risk for mental retardation later in childhood

Data from the population-based Metropolitan Atlanta Developmental Disabilities Study were used in a case-control study to assess the association between low birthweight and mental retardation (intelligence quotient < or = 70) among 10-year-old children who were born in 1975 or 1976. Children with mental retardation were identified from existing records at multiple sources and control children were selected from public school rosters. Data on birthweight and other covariates (sex, birth order, maternal age, maternal race, maternal education and gestational age) came from birth certificates. We used multiple logistic regression modelling to obtain adjusted odds ratios for mental retardation, with normal birthweight children (those weighing > or = 2500 g) as the referent group. For low birthweight children as a whole, the odds ratio for mental retardation was 2.8 (95% CI 1.9-4.2). The risk was higher for very low birthweight (< 1500 g) children than for moderately low birthweight (1500-2499 g) children, and higher for severe mental retardation (intelligence quotient < 50) than for mild mental retardation (intelligence quotient 50-70). Adding gestational age to the models revealed that normal birthweight children who were born preterm also were at increased risk of having mental retardation at age 10 years.

The relationship between maternal education and mental retardation in 10-year-old children

We conducted a case-control study of mental retardation (MR) in which case children (aged 10 years) were identified from existing records at multiple sources, primarily the public school systems. Control children were drawn from a roster of public school students not receiving special education services. We found that maternal educational level at the time of delivery was strongly and inversely related to a form of MR not accompanied by other serious neurologic conditions. For this isolated form of MR, maternal educational level was by far the most important predictor from among seven sociodemographic variables examined. There was a significant race-education interaction that indicated a steeper gradient in risk among white mothers than among black mothers. Relative to children of white mothers with 12 years of education, all children of black mothers, except those whose mothers had 16 or more years of education, were at increased risk. The results may be useful as a guide for selecting high-risk groups as candidates for early childhood intervention programs.

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.

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.

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.

Contribution of developmental disabilities to childhood mortality in the United States: a multiple-cause-of-death analysis

Although developmental disabilities are among the major chronic health problems affecting children in the United States, the contribution of developmental disabilities to childhood mortality is unknown. To investigate the magnitude of this contribution, multiple cause-of-death data were examined for US children, aged 1-19 years, for 1980 and 1983-1989. The following conditions were included as developmental disabilities: autism, attention deficit disorder, learning disorders, mental retardation, cerebral palsy, epilepsy, muscular dystrophy, blindness and deafness. Based on underlying cause only, it was found that developmental disabilities were the fifth leading cause of nontraumatic death for children between 1 and 14 years of age and the third leading cause of non-traumatic death for children between 15 and 19 years. When a multiple cause approach was used to define developmental disability-related deaths (i.e. when contributing as well as underlying cause was considered), the number of such deaths nearly doubled. On the basis of both underlying- and multiple-cause analyses, cerebral palsy was the developmental disability most frequently cited as a cause of death. Mental retardation ranked second according to the multiple-cause approach but only fourth according to the underlying-cause approach. The least frequent causes of death (autism, attention deficit disorder, learning disorders, blindness, and deafness) were the ones most likely to be coded as contributing rather than underlying causes. Developmental disability-related mortality rates were highest among children aged 1-4 and 15-19 years, highest among blacks and lowest among racial groups other than blacks and whites, and higher among males than females. Although results of multiple-cause-of-death analyses more accurately reflect the proportion of deaths related to developmental disabilities, even this approach may underestimate the degree to which mortality is associated with a developmental disability.

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.

Prevalence and health impact of developmental disabilities in US children

OBJECTIVE

Data from the 1988 National Health Interview Survey--Child Health Supplement were used to examine the prevalence of selected developmental disabilities and their impact among children ages 0 through 17 years.

DESIGN

The following conditions, identified through a structured in-person interview with a parent or other adult household member, were examined: deafness or trouble hearing, blindness, epilepsy or seizures, stammering and stuttering, other speech defects, cerebral palsy, delay in growth or development, learning disabilities, and emotional or behavioral problems. The impact was defined by measures of perceived health status, school performance and attendance, and health care utilization.

RESULTS

Seventeen percent of children in the United States were reported to have ever had a developmental disability. The prevalence of the individual disabilities ranged from 0.2% for cerebral palsy to 6.5% for learning disabilities. These conditions taken together had a substantial impact on the health and educational functioning of affected children: 1.5 times more doctor visits, 3.5 times more hospital-days, twice the number of school-days lost, and a 2.5-fold increase in the likelihood of repeating a grade in school compared with children without these conditions. The extent of this impact was much greater among children with multiple disabilities or with either cerebral palsy, epilepsy or seizures, delays in growth and development, or emotional or behavioral problems. The impact on school performance was most pronounced for children reported to have learning disabilities.

CONCLUSIONS

Future research efforts should be focused on ways to reduce the impact of these developmental disabilities on quality of life.

Mental retardation in ten-year-old children in relation to their mothers' employment during pregnancy

We conducted a case-control study to examine relationships between potential risk factors in women's prenatal occupational histories and subsequent mental retardation in their 10-year-old children. Children with mental retardation (intelligence quotient less than 71) were identified from special education records maintained by the public school systems in the metropolitan Atlanta area and from records of various medical and social service agencies serving children with special needs. Control children were chosen from the rosters of 10-year-olds who were enrolled in regular education classes in the local public school systems. To obtain occupational histories, sociodemographic data, and other information, we interviewed 352 natural mothers (67%) of 525 case children and 408 natural mothers (64%) of 636 control children. We computed odds ratios for each of 25 selected occupation, industry, and agent categories controlling for maternal education, birth order, and race. Most comparisons yielded odds ratios that were not indicative of unusual risks, but we did find lower than expected risks among children of teachers and health-care professionals. We also found a strong, positive association between mental retardation and maternal employment in the textile and apparel industries. The findings are useful for planning the direction of future studies of childhood cognitive ability to focus on specific parental occupations or industries.

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.

Self-reported health status of Vietnam veterans in relation to perceived exposure to herbicides and combat

The authors examined how the self-reported health of 7,924 US Army Vietnam veterans in 1985-1986 related to the men's perceived exposure to herbicides and combat in Vietnam. The results showed strong, positive associations between the extent of reported herbicide exposure (classified as a four-level ordinal index) and all 21 health outcomes studied, with clear "dose-response" relations in most instances. In contrast, only chloracne and psychological symptoms, including a symptom pattern consistent with posttraumatic stress disorder, were found to be strongly related to the amount of reported combat exposure (classified as a four-level ordinal index). The multiple herbicide/outcome associations seem implausible because of their nonspecificity and because of collateral biologic evidence suggesting the absence of widespread exposure to dioxin-containing herbicides among US Army combat units. These associations may have resulted from long-term stress reactions that produced somatization, hypochondriasis, and increased utilization of medical care among some Vietnam veterans. The available data suggest, however, that the association between reported combat exposure and psychological symptoms consistent with posttraumatic stress disorder may be causal.

Non-Hodgkin's lymphoma in a cohort of Vietnam veterans

We examined the incidence of non-Hodgkin's lymphoma (NHL) in a cohort of 18,313 United States Army veterans from the Vietnam era. Diagnoses were confirmed through a review of hospital records. Among veterans who had died after discharge or who had participated in a telephone interview (8,170 Vietnam veterans and 7,564 non-Vietnam veterans), seven Vietnam veterans and one non-Vietnam veteran had developed non-Hodgkin's lymphoma (p = 0.07). As none of the NHL cases had military job titles which suggest that they were occupationally exposed to herbicides while in Vietnam, the reasons for the excess are unclear.

Nonresponse and intensity of follow-up in an epidemiologic study of Vietnam-era veterans

Characteristics of nonrespondents, respondents who were easy to locate, and respondents who were hard to locate were examined with the use of data from a telephone health survey of male, US Army, Vietnam-era veterans. Of 17,867 eligible men discharged from active military duty in the late 1960s and early 1970s, 15,288 (86%) were successfully located and interviewed during 1985-1986. Veterans who could not be located were more likely than respondents to possess baseline characteristics predictive of increased mortality. In contrast, subjects who were located but refused to be interviewed were similar to respondents. Among veterans who were interviewed, those who were hardest to locate had the highest prevalence of known risk factors for diminished health status and reported many health problems with higher relative frequencies than respondents who were easier to locate. Odds ratios comparing the prevalence of each of 11 health outcomes in men who had served in Vietnam with that in men who had served elsewhere did not vary appreciably by intensity of follow-up. In particular, the subgroup of respondents that was located and interviewed within 2 weeks of initiation of follow-up (comprising 25% of all respondents) produced odds ratios for 10 of the 11 outcomes that were not appreciably different from odds ratios based on all respondents.

National sources of vital status information: extent of coverage and possible selectivity in reporting

The completeness of death reporting and characteristics of deaths not found by the Social Security Administration, Internal Revenue Service, Veterans Administration, and National Death Index were investigated in a follow-up study (1965-1983) of mortality among 18,313 randomly selected Vietnam-era veterans. Overall, 97% of all known deaths identified by these means had been found by the National Death Index (for the years 1979-1983), 83% by the Social Security Administration files, 80% by the Veterans Administration file, and only 23% by the Internal Revenue Service file. Coverage by the Veterans Administration file differed considerably by time period of death; 28% of deaths occurring in 1965-1971 appeared in the Veterans Administration system compared with 87% in 1972-1983. Social Security Administration coverage varied somewhat over time-87% in the period from 1965-1981 and 64% in 1982-1983. Deaths not found by the National Death Index or the Veterans Administration file occurred more frequently among those with certain characteristics, such as nonwhite racial background, nonhonorable discharge, and low rank at discharge. There were no such differences for deaths found by the Social Security Administration. Importantly, these characteristics were strong predictors of subsequent mortality. Thus, in studies of mortality, there is a potential for bias when certain reporting sources are used to the exclusion of others.

Cancer mortality among northern Georgia carpet and textile workers

Proportionate cancer mortality was analyzed among white male carpet and textile workers in five northwest Georgia counties for the years 1970-1984. Compared with other Georgians, carpet and textile workers had higher proportions of lymphocytic leukemia (proportionate cancer mortality ratio [PCMR] = 2.9; 95% CI = 1.4-5.4]) and testicular cancer (PCMR = 3.2; 95% CI = 1.0-7.5). The excess mortality from lymphocytic leukemia was even higher when the analysis was limited to workers deemed most likely to work directly in production areas (PCMR = 4.2; 95% CI = 1.7-8.7). Further studies are needed to determine if the observed excesses are the result of workplace exposures.

Nasal cancer in the U.S. shoe industry: does it exist?

Studies in England and Italy have demonstrated a striking association between employment in the shoemaking industry and cancer of the nasal cavities and sinuses. However, three recent, large-scale proportionate mortality studies of U.S. shoeworkers do not show any deaths from these tumors. This paper reviews the methodology of those studies, emphasizing the underlying data and statistical power. In addition, epidemiologic and other considerations important in assessing and interpreting the apparent absence of a nasal cancer risk in the U.S. shoe industry are discussed.

Mortality among workers in a shoe manufacturing company

Several epidemiologic studies have suggested that leather workers have an elevated risk of bladder cancer, nasal cancer, and leukemia. A case-control analysis of patient files at a large cancer treatment facility in New York State indicated that several bladder cancer patients had worked at a large shoe manufacturing company in upstate New York. A mortality study was initiated to determine whether there was an unusual cancer risk associated with employment in this facility. Because company records were not available, local newspaper obituaries were used to identify former company employees who died between 1960 and 1979. Proportionate mortality (PMR) analyses were conducted by using 4,734 death certificates and the general U.S. population for comparison. There were no excess deaths from nasal cancer or bladder cancer, and mortality from leukemia was slightly lower than expected. Increased relative frequencies of digestive cancers were seen among men and women. There were significant excesses of deaths from multiple myeloma among both men (PMR = 193) and women (PMR = 346).

Mortality among chemical workers exposed to benzene and other agents

A historical cohort mortality study was conducted of 259 male employees of a chemical plant where benzene has been used in large quantities. The study group included all persons who were employed by the Company any time between January 1, 1947 and December 31, 1960. The cohort was followed through December 31, 1977 at which time 58 known deaths were identified. The only unusual finding was four deaths from lymphoreticular cancers when 1.1 would have been expected on the basis of national mortality rates. Three of the deaths were due to leukemia and one was caused by multiple myeloma. In addition, one of the leukemia deaths had multiple myeloma listed on the death certificate. The findings are consistent with previous reports of leukemia following occupational exposure to benzene and raise the possibility that multiple myeloma could be linked to benzene, also.

Proportionate mortality among US shoeworkers, 1966-1977

Proportionate mortality for various causes was examined among 3,754 decedents (2,144 men, 1,610 women) who had worked in shoe manufacturing plants represented by either of two labor unions in the US. None of the shoeworker deaths were attributed to nasal cancer, whereas 2.2 were expected on the basis of general population data. Mortality from leukemia and cancer of the urinary bladder was not unusual in either sex or either union. However, deaths from cancers of the liver and gallbladder combined were significantly increased among male and female members of one union. Three deaths from mesothelioma were seen among members of this same union. Rectal cancer mortality was higher than expected among men and women in both unions. The findings are at variance with previous reports of high risks of certain cancer sites among shoeworkers. However, results for liver and gallbladder cancer and mesothelioma suggest the possibility that other previously unsuspected hazards may have been present in certain areas of the US shoe industry.