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D A Savitz

Publications and source records attributed to D A Savitz.

At least 145 records · Page 8Linked to original sources
PubMed1994

Prenatal lead exposure in relation to gestational age and birth weight: a review of epidemiologic studies.

Although the adverse effect on pregnancy outcomes at high levels of lead exposure in the workplace has been recognized for years, there is uncertainty regarding the impact of exposure at the lower community exposure levels commonly encountered today. This review summarizes the epidemiologic literature and discusses pertinent methodologic issues and possible sources of interstudy variation. The authors conclude that prenatal lead exposure is unlikely to increase the risk of premature membrane rupture but does appear to increase the risk of preterm delivery. Whether prenatal lead exposure decreases gestational age in terms of infants is unclear. Prenatal lead exposure also appears to be associated with reduced birth weight, but results vary in relation to study design and degree of control for confounding. Adjustment for gestational age, a possible confounder of the birth weight-lead exposure association, did not yield clearer results.

Birth Weight↗
PubMed1994

Organization and classification of work history data in industry-wide studies: an application to the electric power industry.

Industry-based cohort studies require systems for organizing work history data. Although the ultimate goal may be to assess the hazards of specific exposures, classification of the job titles that comprise work histories serves an important descriptive purpose in itself and is often necessary before exposure data can be obtained. A system we have created for organizing jobs in a study of 135,000 workers at five electric power companies highlights conceptual and practical issues in managing work history data for epidemiological studies. Job characteristics including function, location, and authority were used to develop a system of 28 occupational categories. Comprehensibility, flexibility, and efficiency were important criteria in designing the system. Assessment of exposures was an implicit goal; the same categories will define job-exposure matrices for numerous agents. A combination of computer algorithms and expert judgment was used to assign individual job titles to the categories. This system facilitates examining the effects of various agents and controlling for confounding. The 28 categories can be collapsed and regrouped to analyze disease risks in relation to exposures to magnetic fields and other agents; even exposures not previously considered could be brought into the study with this generic system for organizing the electric power industry.

Data Collection↗
PubMed1994

Correlations among indices of electric and magnetic field exposure in electric utility workers.

Power-frequency electric and magnetic fields are known to exhibit marked temporal variation, yet in the absence of clear biological indications, the most appropriate summary indices for use in epidemiologic studies are unknown. In order to assess the statistical patterns among candidate indices, data on 4383 worker-days for magnetic fields and 2082 worker-days for electric fields collected for the Electric and Magnetic Field Project for Electric Utilities using the EMDEX meter [Bracken (1990): Palo Alto, CA: Electric Power Research Institute] were analyzed. We examined correlations at the individual and job title group levels among indices of exposure to both electric and magnetic fields, including the arithmetic mean, geometric mean, median, 20th and 90th percentiles, time above lower cutoffs of 20 V/m and 0.2 microT, and time above higher cutoffs of 100 V/m and 2.0 microT. For both electric and magnetic fields, the arithmetic mean was highly correlated with the 90th percentile; moderately correlated with the geometric mean, median, and lower and higher cutoff scores; and weakly correlated with the 20th percentile. Electric and magnetic field indices were generally weakly correlated with one another. Rank-order correlation coefficients were consistently greater than product-moment correlation coefficients. Job title group summary scores showed higher correlations among electric field indices and magnetic field indices and between electric and magnetic field indices than was found for individual worker-days, with only the 20th percentile clearly independent of the others. These results suggest that individuals' exposures are adequately characterized by a measure of central tendency for electric and magnetic fields, such as the arithmetic or geometric mean, and an indicator of a lower threshold or cutoff for each field type, such as the 20th percentile or proportion of time above 20 V/m or 0.2 microT. A single measure of central tendency for each type of field appears to be adequate when exposures are assessed at the job title level.

Electricity↗
PubMed1994

Residential magnetic fields, wire codes, and pregnancy outcome.

The relationship of measured residential magnetic fields and wire codes to pregnancy outcome was examined in data collected for a study of childhood cancer in Denver. Pregnancies in homes with measured fields above 0.2 microT or high wire codes were not more likely to end in miscarriage, low birth weight, or preterm delivery. Lack of data on potential confounders and small numbers of cases limit the study's conclusions.

Abortion, Spontaneous↗
PubMed1994

Simplification of the Wertheimer-Leeper wire code.

Wire codes, introduced by Wertheimer and Leeper as a surrogate for residential magnetic fields, divide imputed exposure into several categories based on the configurations of electrical wiring within 40 m of homes. Using the data set gathered by Savitz et al. in the Denver, Colorado, area of the United States, we determined which of the wiring attributes that contribute to Wertheimer-Leeper coding are actually associated with low-power magnetic fields measured in bedrooms of subjects. The results led us to propose a considerably simplified three-category form of the Wertheimer-Leeper code that 1) drops the distinctions between thick and thin primary wires and between first-span and other secondary lines, 2) adds a new distinction between open (i.e., conductors not in physical contact) and spun secondaries, and 3) explains as much of the between-home variability in log-transformed bedroom fields as does the five categories of the original Wertheimer-Leeper code. The data necessary to classify residences using the modified code are considerably simpler to obtain and should lead to more reliable results. A separate reanalysis of the Denver data set of Savitz et al, shows that the modified code yields risk estimates that are both precise and markedly elevated for the highest exposure category, suggesting that this code may be useful in other studies.

Colorado↗
PubMed1994

Cured and broiled meat consumption in relation to childhood cancer: Denver, Colorado (United States)

The association between cured and broiled meat consumption by the mother during pregnancy and by the child was examined in relation to childhood cancer. Five meat groups (ham, bacon, or sausage; hot dogs; hamburgers; bologna, pastrami, corned beef, salami, or lunch meat; charcoal broiled foods) were assessed. Exposures among 234 cancer cases (including 56 acute lymphocytic leukemia [ALL], 45 brain tumor) and 206 controls selected by random-digit dialing in the Denver, Colorado (United States) standard metropolitan statistical area were compared, with adjustment for confounders. Maternal hot-dog consumption of one or more times per week was associated with childhood brain tumors (odds ratio [OR] = 2.3, 95 percent confidence interval [CI] = 1.0-5.4). Among children, eating hamburgers one or more times per week was associated with risk of ALL (OR = 2.0, CI = 0.9-4.6) and eating hot dogs one or more times per week was associated with brain tumors (OR = 2.1, CI = 0.7-6.1). Among children, the combination of no vitamins and eating meats was associated more strongly with both ALL and brain cancer than either no vitamins or meat consumption alone, producing ORs of two to seven. The results linking hot dogs and brain tumors (replicating an earlier study) and the apparent synergism between no vitamins and meat consumption suggest a possible adverse effect of dietary nitrites and nitrosamines.

Adolescent↗
PubMed1994

Association between maternal education and infant diarrhea in different household and community environments of Cebu, Philippines.

Maternal education is one of the strongest determinants of infant survival in developing countries, however, questions remain regarding the extent to which its effects vary as a function of contextual variables. In this study, a multi-level interactive model is used to assess whether the protective effect of maternal education on the risk of infant diarrhea is modified by three aspects of the mother's familial and community environment: household assets, community economic resources and the availability of mothers' clubs. 2484 study participants were interviewed in 1984 as part of the Cebu Longitudinal Infant Health and Nutrition Study. The findings suggest that the protective effect of maternal education on infant diarrhea varies according to the socio-economic environment in which the mother lives: maternal education protects against infant diarrhea in the more economically and socially advantaged communities but has no effect in the more disadvantaged communities. The results also indicate that the protective effect of maternal education is smaller in the wealthier households. These data suggest that improvement in maternal education level, alone, may not always have the expected beneficial effects on infant health. Corollary measures to improve access of mothers and children to basic community resources and efforts to help mothers be more effective in their various social roles may be necessary preconditions for higher levels of maternal education to result in improved infant health.

Adult↗
PubMed1994

Completeness of prescription recording in outpatient medical records from a health maintenance organization.

Since validity of drug data is often characterized by the agreement between questionnaire and medical record data, medical record completeness for drug therapy was evaluated. Outpatient medical records of 501 randomly selected Group Health Cooperative Health Maintenance Organization (HMO) participants known to have been dispensed a non-steroidal anti-inflammatory drug (NSAID) were reviewed for completeness. Documentation was also evaluated for indication, age, gender, location of visit, and number of visits. The NSAID was recorded in 89% of the charts reviewed. Charts with a vague/missing diagnosis were more likely to lack documentation [RR (95% CI): 20.0 (13.2-30.3)]. The data suggested that poorer documentation was related to older age [1.5 (0.9-2.5)] but not to gender, indication, location of visit, or number of visits. Presence of an indication was positively correlated to the completeness of drug documentation. According to this staff/group HMO, there may be a higher concordance between self-reported medication use and medical record data than found in previous literature.

Age Factors↗
PubMed1994

Effect of a monetary incentive on response to a mail survey.

We assessed the effect of a $1 incentive on response to a two-page questionnaire which was sent to 8356 female cosmetologists between 22 and 36 years old. The study population was randomly assigned to one of three groups in which a $1 incentive was enclosed with either the first or second mailing, or with none of the mailings. Ten percent of questionnaires were returned by the postal service because of an incorrect address or death of the addressee and were omitted from response calculations. Of the remaining questionnaires, 79% were completed and returned after up to three mailings. The cumulative response was highest among cosmetologists who received a $1 incentive with the first mailing, (81%; 95% confidence interval (CI), 80 to 82), intermediate among those who received $1 with the second mailing (78%, 95% CI, 77 to 79), and lowest among cosmetologists who received no incentive (74%; 95% CI, 70 to 78). Characteristics of cosmetologists who responded after having received a "41 incentive were similar to those who responded without having received an incentive. The higher costs per response incurred by the use of an incentive must be weighed against the benefit of higher response.

Adult↗
PubMed1994

Spontaneous abortions among cosmetologists.

To examine the relation between adverse pregnancy outcomes and work in cosmetology during pregnancy, we conducted a mail survey in North Carolina among 8,356 licensed female cosmetologists 22-36 years of age. We identified pregnancies between 1983 and 1988 by a brief screening questionnaire, followed by a more detailed mail questionnaire. Seventy-four per cent of eligible cosmetologists responded to each inquiry. We restricted the main analysis to 96 cosmetologists with a spontaneous abortion and 547 cosmetologists with a single livebirth who worked full-time in cosmetology or in other jobs during the first trimester of pregnancy. With adjusted odds ratios ranging from 1.4 to 2.0, we found associations between spontaneous abortion and the number of hours worked per day in cosmetology, the number of chemical services performed per week, the use of formaldehyde-based disinfectants, and work in salons where nail sculpturing was performed by other employees. We found no important associations among full-time cosmetologists who performed few chemical services and among cosmetologists who worked less than 35 hours per week.

Abortion, Spontaneous↗
PubMed1994

Vaginal bleeding and adverse reproductive outcomes: a meta-analysis.

The objective of this paper is to characterise and quantify the association between vaginal bleeding and pregnancy outcome. A meta-analysis was performed in order to quantify the risk of adverse reproductive outcome by combining evidence from all previous studies of vaginal bleeding. The reproductive endpoints considered were low birthweight, preterm birth, stillbirth, perinatal death and congenital malformation. The meta-analysis confirms an association of vaginal bleeding with adverse pregnancy outcomes, but identified discrepancies in the reported risks of vaginal bleeding and magnitudes of association between bleeding and adverse reproductive outcomes, observed across studies. These discrepancies may be attributed to inconsistent definitions of the timing and severity of vaginal bleeding. The implications of such inconsistencies are discussed, suggesting a need for more standardised definitions of vaginal bleeding and reproductive endpoints in future studies.

Abortion, Threatened↗
PubMed1994

Employment during pregnancy in relation to risk factors and pregnancy outcome.

OBJECTIVE: To describe the relation of employment status during pregnancy to potential demographic, behavioural and obstetrical risk factors for adverse late pregnancy outcome, as well as the risks of having a preterm delivery and a small for gestational age infant. DESIGN: Cohort study. SETTING: A university hospital. SUBJECTS: Of 8,711 women with singleton pregnancies (1989-91), 5,875 returned questionnaires about risk factors and employment status at 16 and 30 weeks gestation. Of the respondents 5,552 were analysed in five groups: (1) women working throughout pregnancy, (2) women working in the first, but unemployed during the second trimester, (3) women on sick leave in the first and second trimester, (4) women unemployed throughout pregnancy, and (5) students. The association between employment status and having a small for gestational age infant and preterm delivery was evaluated, accounting for other risk factors. RESULTS: Working women and students had the most and unemployed women the least favourable demographic risk factors. Women on sick leave had the least favourable obstetrical and medical history, followed by unemployed women. No clear pattern of the behavioural risk factors was found. Differences in risk of having a small for gestational age infant were a function of parity, smoking and maternal height. Adjustment for these factors plus education yielded a lower risk of preterm delivery in partially unemployed women and higher risk among women on sick leave compared to working women, accounted for by different risks of bleeding in the second and third trimester. CONCLUSIONS: Comparison of pregnancy outcome among women with different work status should consider the differences in risk factor profile. Adjusting for such risk factors, we found no evidence that work per se had any detrimental or beneficial effects on the risk of having a small for gestational age infant or preterm delivery.

Adolescent↗
PubMed1994

The risk of pregnancy-induced hypertension: black and white differences in a military population.

The relationship between race and risk of pregnancy-induced hypertension was investigated in a cohort of active-duty military women who gave birth during the period 1987 through 1989. Cases were identified through hospital discharge diagnoses and included transient gestational hypertension, pre-eclampsia, eclampsia, and unspecified hypertension complicating pregnancy. Multivariate analysis showed nulliparous Black women to be at a slightly increased risk for all pregnancy-induced hypertension (risk ratio [RR] = 1.2) and for pre-eclampsia (RR = 1.3) compared with nulliparous White women. Black parous women were found to have a slightly reduced risk of all pregnancy-induced hypertension (RR = 0.77) and pre-eclampsia (RR = 0.38) compared with White parous women.

Adolescent↗
PubMed1994

Effect of incomplete exposure assessment on epidemiologic dose-response analyses.

OBJECTIVES: When potentially hazardous agents have multiple environmental sources, failure to include all exposure sources can constitute a type of measurement error. In addition, the effects of exposure from one source can also be confounded by exposure to other sources of the same agent. In this study clarification of these concepts is sought, and the direction and magnitude of the resulting bias in epidemiologic measures of association are examined. METHODS: The bias in dose-response functions when the exposure data omit some sources of the agent was estimated with linear and log-linear models to compute risk differences and risk ratios under different assumptions about the magnitude and correlation of exposures from measured and unmeasured sources. RESULTS: With unmeasured exposure of constant magnitude, there is no bias when a measure of association of the appropriate form (difference measures for additive dose-response processes, ratios for multiplicative ones) is selected. When the magnitude of unmeasured exposure varies, the results is nondifferential measurement error that can bias observed dose-response relations upward or downward, depending on the pattern of measurement error and the measure of association. CONCLUSIONS: Failure to measure all sources of exposure to an agent and account for them in the analysis can bias the results of epidemiologic studies. When it is not feasible to measure all exposure sources, the magnitude of bias can be predicted by estimating the distribution of omitted exposures from external data or substudies. Sensitivity analyses are particularly useful for estimating the direction and magnitude of potential bias from incomplete exposure assessment.

Bias↗
PubMed1994

Galactose consumption, metabolism, and follicle-stimulating hormone concentrations in women of late reproductive age.

OBJECTIVE: To test the hypothesis that high galactose consumption and low activity of galactose-1-phosphate uridyl transferase (transferase) is associated with early ovarian senescence among nongalactosemic women. DESIGN: Cross-sectional study. Data collection consisted of a self-administered questionnaire with sections on diet (food frequency data to measure galactose consumption), reproductive, and medical histories. One blood sample was collected to measure FSH and transferase activity; FSH was used as a measure of ovarian senescence. Among women who were having menstrual periods at least every 8 weeks, the blood sample was drawn in the early follicular phase (days 2 to 4) of a menstrual cycle. PARTICIPANTS: Two hundred ninety-five women volunteers ages 38 to 49 years who had not had a hysterectomy or oophorectomy were recruited through posters and advertisements. MAIN OUTCOME MEASURE: Serum FSH concentrations. RESULTS: Controlling for age, smoking, and body mass, transferase activity and FSH were unrelated. However, FSH levels were 29% higher (95% confidence intervals, 9% to 52%) among women who reported consuming > or = 6 g galactose/d. CONCLUSION: These data do not support the hypothesis that low transferase activity represents a genetic predisposition for early ovarian senescence, as measured by FSH levels in women ages 38 to 49 years. However, the hypothesized positive association between galactose consumption and FSH was supported.

Adult↗
PubMed1993

Cautions in the use of antecedents as surrogates for confounders.

When lacking information on confounding variables, epidemiologists have used surrogates which are antecedents of both the exposures and confounders of interest. The usefulness of this strategy is explored in a series of scenarios for a prospective epidemiologic study wherein risk ratios relating antecedent to confounder, antecedent to exposure, and confounder to exposure were varied. Antecedent-adjusted, confounder-adjusted, and crude risk ratios were calculated and compared. The antecedent-adjusted risk ratio was useful, that is, was closer to the confounder-adjusted risk ratio than was the crude risk ratio, in 1,067 (49%) of 2,187 scenarios. The antecedent-adjusted risk ratio, the crude risk ratio, and the risk ratio relating confounder to exposure together predicted the usefulness of the antecedent (or any variable) as a confounder proxy. The antecedent was useful in 97% of scenarios wherein: 1) the antecedent-adjusted risk ratio was less than the crude risk ratio, and the risk ratio relating confounder to exposure was greater than 1.0, or 2) the antecedent-adjusted risk ratio was greater than the crude risk ratio, and the risk ratio relating confounder to exposure was less than 1.0. In the remaining scenarios, it was useful only 5% of the time.

Causality↗