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Biomedical subjects

A Leviton

Publications and source records attributed to A Leviton.

At least 145 records · Page 8Linked to original sources
PubMed1985

Environmental correlates of infant blood lead levels in Boston.

From a blood lead survey of 11,837 births, 249 newborns were enrolled in a 2-year, longitudinal study. Their blood leads (PbB) were measured semiannually, and their homes were visited for repeated collections of dust, soil, indoor air, tap water, and paint. Recent refinishing activity and the sizes of nearby streets were recorded. Overall mean PbB was 7.2 micrograms/dl (SD = 5.3) at birth. PbB did not vary systematically with age. Each subject's average postnatal PbB correlated highly with the amount of lead in dust (r = 0.4, P less than 0.0001) and soil (r = 0.3, P less than 0.001), and with the lead in paint (r = 0.2, P less than 0.01). Dust, soil and air lead levels correlated with one another. Refinishing activity in the presence of lead paint was associated with elevations of PbB. Water lead, proximate traffic, weight of recovered dust, race, maternal age and education, and sex were not predictive of PbB. Multivariate models of PbB were constructed that become increasingly predictive with age (r2 = 20 to 37%). Indoor dust lead, lead in soil, refinishing activity, and season were the independent variables.

Air Pollutants↗
PubMed1985

Methodological issues in modeling the relationship between low-level lead exposure and infant development: examples from the Boston Lead Study.

This paper addresses several methodological issues relevant to an assessment of the association between low-level lead exposure and early development. In particular, we discuss methods for choosing, from a large pool of candidates, the covariates to control when estimating this association. We examine the issue of confounding and explain why adjusting increased, rather than decreased, the estimate of the association between blood lead level and development at 6 months of age in our sample. A step-by-step description of our strategy for model building is presented. Finally, we demonstrate the robustness of the findings by showing that the magnitude and standard error of the estimated lead effect is not affected appreciably by the method of selecting covariates to be controlled for or by the characterization of lead as a continuous, ordinal, or dichotomous variable. Although these issues arose in the course of analyses of data collected by the Boston lead study (D. Bellinger, H. Needleman, A. Leviton, C. Waternaux, M. Rabinowitz, and M. Nichols (1984), Neurobehav. Tox. Teratol., 6, 387-402), they apply to other current prospective lead studies as well.

Analysis of Variance↗
PubMed1985

Posttraumatic seizures: an assessment of the epidemiologic literature.

Confusion about the risk of seizures following head trauma might in part reflect methodologic limitations of reported studies. This epidemiologic review emphasizes four methodologic issues: selection of cases, selection of controls, definition and ascertain of seizures, and definition, of seizures, and definition, classification, and ascertainment of trauma. Although the focus of this review is a set of reports of civilian injuries, the relevance of war studies to civilian injuries is also discussed.

Adult↗
PubMed1985

Home refinishing, lead paint, and infant blood lead levels.

We measured the blood lead levels of 249 infants semi-annually from birth to two years of age; we sampled the home paint and recorded any recent home refinishing activity. Mean blood lead from birth to age 2 years did not vary systematically with age but did correlate significantly with the amount of lead in the indoor paint (p less than .01). Refinishing activity in homes with high lead paint was associated with elevations of blood lead averaging 69 per cent.

Adult↗
PubMed1984

The relationship between prenatal exposure to lead and congenital anomalies.

We obtained umbilical cord blood from 5,183 consecutive deliveries of at least 20 weeks' gestation and analyzed them for lead concentration. Those demographic and socioeconomic variables, including lead, which were shown on univariate analysis to be associated with increased risk for congenital anomalies were evaluated and controlled by entering them into a stepwise logistic-regression model with malformation as the outcome. Coffee, alcohol, tobacco, and marijuana use, which were associated with lead level, but not risk of malformation, were also controlled. The model was reduced in steps by eliminating the variables with the highest P value, until the most parsimonious model was created. The relative risk for anomalies associated with lead was then calculated while holding other covariates constant. Lead was found to be associated, in a dose-related fashion, with an increased risk for minor anomalies.

Abnormalities, Drug-Induced↗
PubMed1984

Age-related headache characteristics.

A computerized headache interview was completed by 255 children, adolescents, and adults. Children did not differ from adults in the frequency of auras or prodromes. Young children were more likely than older patients to have brief headaches and headaches that tended to occur on weekdays, and to feel "great" after a headache. They were less likely than older patients to acknowledge multiple kinds of headaches, headaches located on one side of the head or posteriorly, and such concomitant occurrences as blurring, photophobia, irritability, frustration-anger, light-headedness, trouble with concentration, numbness-tingling, and lack of appetite. We do not know how much these differences can be attributed to age-related differences in language, physiology, or medical care selection factors.

Adolescent↗
PubMed1984

Acquired perinatal leukoencephalopathy.

Between 36 and 44 weeks after conception, telencephalic white matter in the newborn appears to be particularly vulnerable to insults that result in morphological disturbances. Available evidence indicates that this disorder (or group of disorders), named acquired perinatal leukoencephalopathy, reflects a decrease in blood flow through the distal vessels supplying paraventricular white matter and/or a metabolic disturbance produced by, or in response to, an infectious agent. Major advances in our understanding of the causes, mechanisms, and sequelae of acquired perinatal leukoencephalopathy may be made in the next decade because of improvement in brain imaging techniques, improved survival of high-risk babies, and relatively routine follow-up of these high-risk babies.

Brain↗
PubMed1983

Childhood brain tumor update.

In this review of recent studies of the cerebellar tumors of childhood we have discussed the limitations of traditional approaches to the classification of childhood brain tumors for the purposes of estimating prognosis. While these traditional approaches have provided considerable information about cells of origin, they have left behind the ancient tradition of pathology of considering the tumor in all its aspects, not just its histologic features. As an alternative we have introduced an approach that does not depend ona priori assumptions but rather allows prognosis to be estimated directly from histologic features or from clusters of histologic, clinical, and surgical features-- namely the use clustering strategies as applied to the cerebellar tumors. We have also discussed the preliminary work of the Childhood Brain Tumor Consortium, which has collected a large amount of data to serve as a source of prognostic information in the design of studies of alternative therapies. The preliminary data indicate that there is a disquietingly wide array of overlapping histologic features in three common childhood brain tumors-- medulloblastomas, pilocytic astrocytomas, and ependymomas. Clinicians who seek to reduce the number of deaths among children with brain tumors need specific prognostic information to decide among alternative therapies and to design studies of therapies for biologically homogeneous tumors, rather than studies of therapies of tumor "names" that encompass extraordinarily wide ranges of histologic features. Clinicians must also be extremely wary of "historical" controls; they cannot allow themselves to fall into the trap of believing that a new therapy is better because their patients "would have been expected" to have succumbed sooner. For each proposed therapy new studies must be designed, each with its control population, no matter how difficult this is. Historical controls assume that 1) the tumors were classified properly, 2) the sites of the tumors in different groups of patients were comparable, and 3) tumors with the same name (each encompassing an extremely wide range of histologic features) are comparable in every histologic respect to the study population, and 4) the outlook for patients with tumors with this name has not changed over the half century since the name came into common usage (i.e., that the morbidity associated with these tumors has not changed). For these reasons the use of historical controls must be condemned and all studies of therapies based on such controls discarded. Studies of therapies must compare populations of patients homogeneous as to site, histologic features, and such clinical features as age.

Astrocytoma↗