Biomedical subjects

G M Shaw

Publications and source records attributed to G M Shaw.

223 records · Page 13Linked to original sources

PubMedDate not supplied

Epidemiologic research using existing databases of environmental measures.

When detailed information on individuals is not available, databases of environmental measures are sometimes used in epidemiologic studies to provide data on human exposure. The use of such databases is based on the assumption that the data are representative of individual human exposure and are applicable to the study. Twenty-six databases that contained data on the environment pertaining to California were summarized and evaluated by categorical criteria of spatial and temporal precision, availability, amount of quantitative information, "machine-readability," and type of environmental measure.

California↗

PubMedDate not supplied

Detection of excess disease near an exposure point: a case study.

Many studies have evaluated the likelihood of adverse health effects associated with environmental contamination from point source exposures. Two statistical measures used in these studies are the ratio, R, of the observed to the expected number of cases occurring in the area containing the point and the average distance, D, between the cases and the point. This paper estimates the probability of detecting an association between disease and exposure when one actually exists (power) for R and D for several specific and plausible statistical models. Results are presented in the context of rare diseases such as congenital malformations. The practical implications of using these measures for the evaluation of risk of disease in environmental epidemiologic investigations are discussed.

California↗

PubMedDate not supplied

Congenital malformations and birthweight in areas with potential environmental contamination.

Public concern exists about the potential for reproductive damage that may result from exposures to environmental contaminants. Therefore, the authors sought to determine if there was an association between a child's congenital malformation or a child's lowered weight at birth and his or her mother's residence in a census tract where a site of environmental contamination had been documented. Exposure designations were derived from existing sources of information. Except for an elevated risk (odds ratio = 1.5) for infants with malformations of the heart and circulatory system, this investigation did not reveal increased risks for most malformations or for lowered birthweight among babies born to women who lived in these census tracts. Methodologic issues inherent to investigations that rely on existing data sources are discussed.

Birth Weight↗

PubMedDate not supplied

Residential mobility during pregnancy for mothers of infants with or without congenital cardiac anomalies: a reprint.

Maternal residence at time of delivery is sometimes used as a proxy for residence during early pregnancy to estimate environmental exposures. Residential addresses during time of conception through the first trimester were obtained from mothers of 152 infants with congenital cardiac anomalies and 175 controls, and they were compared with the addresses at delivery abstracted from birth certificates. An estimated 24.8% (95% CI = 20.3, 29.9) of women moved between the time of conception and delivery, and the percentage of cases and controls who moved was similar. Use of address at time of delivery may reduce the likelihood of finding an association between a congenital malformation and a maternal environmental exposure.

Adult↗

PubMedDate not supplied

Role of exposure databases in epidemiology.

At present, exposure databases record data primarily for regulatory purposes; they have not focused on serving the needs of epidemiologists or public health. However, the modification of exposure databases could facilitate their use in epidemiology. Characteristics necessary to enhance the use of all databases include easy access by users; documentation of methods, sampling bias, error, and inconsistences; widespread coverage in time and space; and methods and measures for estimating exposure of individuals as well as populations. Also needed are exposure scenarios and models to estimate exposures for geographic areas and time intervals not currently sampled. Multidisciplinary teams are needed to examine current databases, to review strategies for improving data collection, and to suggest and help implement appropriate changes. A long-term goal is to develop and validate data from exposure scenarios and models using data on the relationship of exposure to doses measured in humans.

Databases, Factual↗

PubMedDate not supplied

Exposure misclassification due to residential mobility during pregnancy in epidemiologic investigations of congenital malformations.

This study addressed the question of how maternal migration between conception and birth affects estimates of risk in studies of congenital malformations when movement is related to the exposure. For example, in studying the potential association between proximity to a chemical waste site and the occurrence of birth defects, incorrect inferences might be drawn if maternal residence at birth was used as a surrogate for exposure at conception in the case when a significant amount of media attention influenced some women to move away from the site after becoming pregnant. A simple statistical model is proposed that defines the distance to a fixed exposure point measured at birth as a function of the distance to the point measured at conception, the probability of movement, the direction of movement, and the distance moved. Bias is the difference between the expected results when distance is measured at birth versus conception. The amount of bias can be substantial for movement patterns that may be likely to occur. This simplified model was used in an effort to explore and better understand the relationships between maternal migration and risk.

Abnormalities, Drug-Induced↗

PubMedDate not supplied

Mothers' motivations to participate in a pregnancy health survey.

An important question in interpreting epidemiologic data is why some persons agree to participate in a health survey while others do not. Information about why people agree to interview or answer a questionnaire could help researchers to devise procedures for a health survey and to chose information to be communicated in the interview or questionnaire so as to increase subjects' participation. The authors interviewed 180 mothers who gave birth to a child with a birth defect and 198 mothers whose children were born without a birth defect. The interviews were part of two case-control studies to determine risk factors for selected birth defects. In the course of the interviews, each mother was asked why she agreed to be interviewed, and whether anything about the survey procedures that were followed could be improved. Among both the case mothers and the control mothers the most common reason for agreeing to be interviewed was humanitarian, expressed as "to help others" or "to prevent what happened to my baby from happening to babies in the future." Case mothers, more frequently than control mothers, gave as their reason for participating either to help themselves, their child, their family, or to further scientific understanding. Emphasizing these as benefits of participation to those who are survey subjects at the time of the initial contact could increase the proportion who agree to respond.

Altruism↗