Biomedical subjects

D A Savitz

Publications and source records attributed to D A Savitz.

At least 19 recordsLinked to original sources

PubMed2005

Relation between ambient air quality and selected birth defects, seven county study, Texas, 1997-2000.

A population-based case-control study investigated the association between maternal exposure to air pollutants, carbon monoxide, nitrogen dioxide, ozone, sulfur dioxide, and particulate matter <10 microm in aerodynamic diameter during weeks 3-8 of pregnancy and the risk of selected cardiac birth defects and oral clefts in livebirths and fetal deaths between 1997 and 2000 in seven Texas counties. Controls were frequency matched to cases on year of birth, vital status, and maternal county of residence at delivery. Stationary monitoring data were used to estimate air pollution exposure. Logistic regression models adjusted for covariates available in the vital record. When the highest quartile of exposure was compared with the lowest, the authors observed positive associations between carbon monoxide and tetralogy of Fallot (odds ratio = 2.04, 95% confidence interval: 1.26, 3.29), particulate matter <10 microm in aerodynamic diameter and isolated atrial septal defects (odds ratio = 2.27, 95% confidence interval: 1.43, 3.60), and sulfur dioxide and isolated ventricular septal defects (odds ratio = 2.16, 95% confidence interval: 1.51, 3.09). There were inverse associations between carbon monoxide and isolated atrial septal defects and between ozone and isolated ventricular septal defects. Evidence that air pollution exposure influences the risk of oral clefts was limited. Suggestive results support a previously reported finding of an association between ozone exposure and pulmonary artery and valve defects.

Air Pollutants↗

PubMed2004

Pesticide use and menstrual cycle characteristics among premenopausal women in the Agricultural Health Study.

Menstrual cycle characteristics may have implications for women's fecundability and risk of hormonally related diseases. Certain pesticides disrupt the estrous cycle in animals. The authors investigated the cross-sectional association between pesticide use and menstrual function among 3,103 women living on farms in Iowa and North Carolina. Women were aged 21-40 years, premenopausal, not pregnant or breastfeeding, and not taking oral contraceptives. At study enrollment (1993-1997), women completed two self-administered questionnaires on pesticide use and reproductive health. Exposures of interest were lifetime use of any pesticide and hormonally active pesticides. Menstrual cycle characteristics of interest included cycle length, missed periods, and intermenstrual bleeding. The authors used generalized estimating equations to assess the association between pesticide use and menstrual cycle characteristics, controlling for age, body mass index, and current smoking status. Women who used pesticides experienced longer menstrual cycles and increased odds of missed periods (odds ratio = 1.5, 95% confidence interval: 1.2, 1.9) compared with women who never used pesticides. Women who used probable hormonally active pesticides had a 60-100% increased odds of experiencing long cycles, missed periods, and intermenstrual bleeding compared with women who had never used pesticides. Associations remained after control for occupational physical activity.

Adult↗

PubMed2004

Risk factors for preterm birth in Vietnam.

OBJECTIVE: To identify the risk of preterm birth and possible determinants among women in Hanoi, Vietnam. METHOD: Prospective cohort study of 1709 women with singleton live births at Hanoi Obstetrics and Gynecology Hospital, Hanoi, Vietnam, June-October 2002. Logistic regression analysis was used to examine predictors of preterm birth (<37 weeks' gestation). RESULT: The risk of preterm birth was 11.8%. Physically demanding work during pregnancy, two or more prior spontaneous abortions, history of preterm birth, vaginal bleeding, inadequate prenatal care during the first 20 weeks of gestation, and history of intrauterine device use with removal less than 12 months before the current pregnancy were associated with increased risk of preterm birth (adjusted odds ratios between 1.8 and 2.6). CONCLUSION: Preterm birth is relatively frequent in this population. Beyond established risk factors, these data implicated agricultural work and physical work demands with preterm birth, as well as history of recent IUD use.

Abortion, Spontaneous↗

PubMed2004

Assessing spatial fluctuations, temporal variability, and measurement error in estimated levels of disinfection by-products in tap water: implications for exposure assessment.

AIMS: To assess spatial fluctuations, temporal variability, and errors due to sampling and analysis in levels of disinfection by-products in routine monitoring tap water samples and in water samples collected in households within the same distribution system for an exposure assessment study. METHODS: Mixed effects models were applied to quantify seasonal effects and the degree to which trihalomethane (THM) levels vary among households or locations relative to variation over time within seasons for any given location. In a separate analysis, the proportion of total variation due to measurement error arising from sampling and analysis was also quantified. RESULTS: THM levels were higher in the summer relative to other seasons. Differences in the relative magnitude of the intra- and inter-household components of variation were observed between the two sets of THM measurements, with a greater proportion of the variation due to differences within seasons for the routine monitoring data and a greater proportion of the variation due to differences across locations for the exposure assessment study data. Such differences likely arose due to differences in the strategies used to select sites for sampling and in the time periods over which the data were collected. With the exception of bromodichloromethane, measurement errors due to sampling and analysis contributed a small proportion of the total variation in THM levels. CONCLUSIONS: The utility of routine monitoring data in assigning exposure in epidemiological studies is limited because such data may not represent the magnitude of spatial variability in levels of disinfection by-products across the distribution system. Measurement error contributes a relatively small proportion to the total variation in THM levels, which suggests that gathering a greater number of samples over time with fewer replicates collected at each sampling location is more efficient and would likely yield improved estimates of household exposure.

Chlorine↗

PubMed2003

Maternal stress and preterm birth.

This study examined a comprehensive array of psychosocial factors, including life events, social support, depression, pregnancy-related anxiety, perceived discrimination, and neighborhood safety in relation to preterm birth (<37 weeks) in a prospective cohort study of 1,962 pregnant women in central North Carolina between 1996 and 2000, in which 12% delivered preterm. There was an increased risk of preterm birth among women with high counts of pregnancy-related anxiety (risk ratio (RR) = 2.1, 95% confidence interval (CI): 1.5, 3.0), with life events to which the respondent assigned a negative impact weight (RR = 1.8, 95% CI: 1.2, 2.7), and with a perception of racial discrimination (RR = 1.4, 95% CI: 1.0, 2.0). Different levels of social support or depression were not associated with preterm birth. Preterm birth initiated by labor or ruptured membranes was associated with pregnancy-related anxiety among women assigning a high level of negative impact weights (RR = 3.0, 95% CI: 1.7, 5.3). The association between high levels of pregnancy-related anxiety and preterm birth was reduced when restricted to women without medical comorbidities, but the association was not eliminated. The prospective collection of multiple psychosocial measures on a large population of women indicates that a subset of these factors is associated with preterm birth.

Adolescent↗

PubMed2002

Study of high- and low-current-configuration homes from the 1988 Denver Childhood Cancer Study.

An epidemiological study conducted by Savitz et al. reported that residential wire codes were more strongly associated with childhood cancer than were measured magnetic fields, a peculiar result because wire codes were originally developed to be a surrogate for residential magnetic fields. The primary purpose of the study reported here, known as the Back to Denver (BTD) study, was to obtain data to help in the interpretation of the original results of Savitz et al. The BTD study included 81 homes that had been occupied by case and control subjects of Savitz et al., stratified by wire code as follows: 18 high current configuration (HCC) case homes; 20 HCC control homes; 20 low current configuration (LCC) case homes; and 23 LCC control homes. Analysis of new data acquired in these homes led to the following previously unpublished conclusions. The home-averaged (i.e., mean of fields measured in subjects' bedrooms, family/living rooms, and rooms where meals normally eaten) spot 60 Hz, 180 Hz, and harmonic (i.e., 60-420 Hz) magnetic fields were associated with wire codes. The 180 Hz and harmonic components, but not the 60 Hz component, were associated with case/control status. Measured static magnetic fields were only weakly correlated (rapproximately 0.2) between rooms in homes. The BTD data provide little support for, but are too sparse to definitively test, the 1995 resonance hypothesis proposed by Bowman et al. Case and control homes had similar concentrations of copper in their tap water. Copper concentration was not associated with wire codes nor with the level of electric current carried by a home's water pipe. These results of the BTD study suggest that future case/control studies investigating power frequency magnetic fields might wish to include measurements of 180 Hz or harmonic magnetic fields in order to examine their associations (if any) with disease status.

Case-Control Studies↗

PubMed2001

Parental occupational exposures to chemicals and incidence of neuroblastoma in offspring.

To evaluate the effects of parental occupational chemical exposures on incidence of neuroblastoma in offspring, the authors conducted a multicenter case-control study, using detailed exposure information that allowed examination of specific chemicals. Cases were 538 children aged 19 years who were newly diagnosed with confirmed neuroblastoma in 1992-1994 and were registered at any of 139 participating hospitals in the United States and Canada. One age-matched control for each of 504 cases was selected through random digit dialing. Self-reported exposures were reviewed by an industrial hygienist, and improbable exposures were reclassified. Effect estimates were calculated using unconditional logistic regression, adjusting for child's age and maternal demographic factors. Maternal exposures to most chemicals were not associated with neuroblastoma. Paternal exposures to hydrocarbons such as diesel fuel (odds ratio (OR) = 1.5; 95% confidence interval (CI): 0.8, 2.6), lacquer thinner (OR = 3.5; 95% CI: 1.6, 7.8), and turpentine (OR = 10.4; 95% CI: 2.4, 44.8) were associated with an increased incidence of neuroblastoma, as were exposures to wood dust (OR = 1.5; 95% CI: 0.8, 2.8) and solders (OR = 2.6; 95% CI: 0.9, 7.1). The detailed exposure information available in this study has provided additional clues about the role of parental occupation as a risk factor for neuroblastoma.

Adolescent↗

PubMed2001

Comparison of assessment methods for pesticide exposure in a case-control interview study.

In epidemiologic studies, much of the variation in disease risk estimates associated with occupational pesticide exposure may be due to variation in exposure classification. The authors compared five different methods of using interview information to assess occupational pesticide exposure in a US-Canada case-control study of neuroblastoma (1992-1994). For each method, exposure assignment was compared with that of a reference method, and neuroblastoma effect estimates were calculated. Compared with the reference method, which included a complete review of occupation, industry, job tasks, and exposure-specific activities, the use of occupation-industry groups alone or in combination with general job task information diluted the exposed group by including individuals who were unlikely to have been truly exposed. The effect estimates representing associations between each exposure method and neuroblastoma were different enough to influence the study's conclusions, especially when the exposure was rare (for maternal occupational pesticide exposure, the odds ratio was 0.7 using the reference exposure assessment method and 3.2 using the occupation-industry group exposure assessment method). Exposure-specific questions about work activities can help investigators distinguish truly exposed individuals from those who report exposure but are unlikely to have been exposed above background levels and from those who have not been exposed but are misclassified as exposed because of their employment in an occupation-industry group determined a priori to be exposed.

Adult↗

PubMed2001

Invited commentary: electromagnetic fields and cancer in railway workers.

The ideal study of occupational exposure to electromagnetic fields and cancer risk would have a clear exposure source, historically stable exposures, and comparable groups of exposed and unexposed workers. Cohorts of railway workers have marked exposure contrasts and limited job changes and provide marginally adequate study sizes, but there have been important changes in their exposures over time, and the field frequency involved is unusual. The results of Minder and Pfluger's study (Am J Epidemiol 2001;153:825--35) add modest support for an association between electromagnetic field exposure and leukemia. However, given the large size and high quality of a number of previous studies of occupational electromagnetic field exposure and cancer, additional studies similar to past ones are unlikely to yield important new insights.

Causality↗

PubMed2001

Human visual function in the North Carolina clinical study on possible estuary-associated syndrome.

The U.S. Environmental Protection Agency assisted the North Carolina Department of Health and Human Services in conducting a study to investigate the potential for an association between fish kills in the North Carolina estuary system and the risk for persistent health effects. Impetus for the study was recent evidence suggesting that estuarine dinoflagellates, including members of the toxic Pfiesteria complex (TPC), P. piscicida and P. schumwayae, may release a toxin(s) that kills fish and adversely affects human health. This report describes one component of the study in which visual system function was assessed. Participants working primarily in estuaries inhabited by TPC or in off-shore waters thought not to contain TPC were studied. The potentially exposed estuary (n = 22) and unexposed offshore (n = 20) workers were matched for age, gender, and education. Visual acuity did not differ significantly between the cohorts, but visual contrast sensitivity (VCS), an indicator of visual pattern-detection ability for stimuli of various sizes, was significantly reduced by about 30% in the estuary relative to the offshore cohort. A further analysis that excluded participants having a history possibly predictive of neuropsychological impairment showed a similar VCS reduction. Additional analyses indicated that differences between the cohorts in age, education, smoking, alcohol consumption, and total time spent on any water did not account for the difference in VCS. Exploratory analyses suggested a possible association between the magnitude of VCS reduction and hours spent in contact with a fish kill. The profile of VCS deficit across stimulus sizes resembled that seen in organic solvent-exposed workers, but an assessment of occupational solvent, and other neurotoxicant, exposures did not indicate differences between the cohorts. These results suggest that factor(s) associated with the North Carolina estuaries, including the possibility of exposure to TPC toxin(s), may impair visual system function.

Analysis of Variance↗

PubMed2001

Frequency of eating during pregnancy and its effect on preterm delivery.

Frequency of eating or meal patterns during pregnancy may be a component of maternal nutrition relevant to pregnancy outcome. To identify meal patterns of pregnant women and investigate the relation between these meal patterns and preterm delivery, the authors performed an analysis using data from the Pregnancy, Infection, and Nutrition Study (n = 2,065). Women recruited from August 1995 to December 1998 were categorized by meal patterns on the basis of their reported number of meals (breakfast, lunch, and dinner) and snacks consumed per day during the second trimester. An optimal pattern was defined according to the Institute of Medicine recommendation of three meals and two or more snacks per day. In this population, 72 percent of the women met this recommendation, and 235 delivered preterm. Women who consumed meals/snacks less frequently were slightly heavier prior to pregnancy, were older, and had a lower total energy intake. In addition, these women had a higher risk of delivering preterm (adjusted odds ratio = 1.30, 95 percent confidence interval: 0.96, 1.76). There was no meaningful difference in the risk by early versus late preterm delivery, but those who delivered after premature rupture of the membranes (adjusted odds ratio = 1.87, 95 percent confidence interval: 1.02, 3.43) had a higher risk than those who delivered after preterm labor (adjusted odds ratio = 1.11, 95 percent confidence interval: 0.64, 1.89). This study supports previous animal model work of an association between decreased frequency of eating and preterm delivery.

Adolescent↗

PubMed2001

Do studies of wire code and childhood leukemia point towards or away from magnetic fields as the causal agent?

A long-standing point of controversy in the epidemiologic literature concerns the meaning of a wire code-childhood leukemia association for assessing the role of magnetic field exposure. Six studies of wire codes and childhood leukemia in North America were examined, three of which reported positive associations and all of which found some relation between wire codes and measured magnetic fields. Supporting magnetic fields as the basis for the wire code associations are the correspondence between those wire code levels which predict distinct magnetic fields and those which predict leukemia risk in the positive studies. Geographic locations and methods that refine wire codes as magnetic fields predictors also tend to strengthen the association with leukemia. Opposing arguments are based on the failure of the wire code-magnetic field association to predict the strength of association across studies, including the unexplained lack of association between wire codes and leukemia in the Midwest and in Canada. Alternatives to magnetic fields are less supported; residential mobility, social class, and neighborhood characteristics are unlikely to explain a wire code effect. Ambiguity persists because of the modest strength of the wire code-leukemia association, the complexity of the relation between wire codes and magnetic fields, lack of knowledge of risk factors for childhood leukemia, and the limited evaluation of wire code correlates other than magnetic fields.

Canada↗

PubMed2001

Mortality patterns by occupation in a cohort of electric utility workers.

BACKGROUND: Mortality patterns were examined in a United States cohort of 138,905 male electric utility workers from five companies to help interpret previous studies of health effects in this industry. METHODS: Using Poisson regression techniques, internal cohort analyses examined total mortality, cardiovascular disease, and cancer in relation to duration of employment in each of nineteen occupational categories which comprise utility operations. RESULTS: Relative to workers who were never involved in utility operations (e.g., administrative workers), mortality rate ratios among operations workers were higher for total mortality, cardiovascular disease, and total cancer. Lung cancer risk was consistently elevated, whereas increased mortality for other cancers was less consistent. CONCLUSIONS: The results of this study indicate excess risk of total mortality, cardiovascular disease, and some cancers among electric utility workers, which could be related to both occupational and non-occupational risk factors.

Adult↗

PubMed2001

Sexual activity during late pregnancy and risk of preterm delivery.

OBJECTIVE: To examine the association between sexual activity during late pregnancy and preterm delivery. METHODS: Women at least 16 years old and carrying singleton fetuses were recruited between 24 and 29 weeks' gestation from prenatal clinics in central North Carolina. They were interviewed by telephone about sexual activity before and during pregnancy. One hundred eighty-seven women delivered between 29 and 36 weeks and had a follow-up interview after delivery. Four hundred nine women who were selected randomly from the cohort served as controls and had a follow-up interview between 29 and 36 weeks (mean gestational age 39.2 weeks). RESULTS: Intercourse during late pregnancy was associated with a reduced risk of preterm delivery. The conditional odds ratio (OR) was 0.34 and 95% confidence interval (CI) 0.23, 0.51 for preterm delivery within 2 weeks after intercourse. Similar decreased risk for preterm delivery was found with recent female orgasm. Adjusting for race, age, education, and living with a partner had little effect on results. Cases were more likely than controls to report poorer health, medical reasons for reducing sexual activity, less interest in sex, and receipt of advice to restrict sexual activity during pregnancy. Results did not differ substantially according to presence or absence of bacterial vaginosis at 28 weeks. CONCLUSION: These data provide evidence against the hypothesis that sexual activity generally increases risk of preterm delivery between 29 and 36 weeks. However, we cannot exclude the possibility that a small subgroup of susceptible women might have adverse consequences of sexual activity.

Adult↗

PubMed2001

Reproducibility of reported farming activities and pesticide use among breast cancer cases and controls. A comparison of two modes of data collection.

PURPOSE: Farming is associated with exposure to many potential hazards including pesticides and other agents, but the quality of self-reported data on farm exposures has not been well studied. METHODS: The reproducibility of self-reported farming history was evaluated among women in a population-based, case-control study of breast cancer in North Carolina. Thirty cases and 31 controls were randomly re-interviewed by telephone an average of 13.8 months after the initial interview. The initial interview was based on a farm-by-farm questionnaire, while the repeat interview was based on a shorter ever/never questionnaire. Agreement was estimated using proportions in exact agreement, kappa (kappa), and intraclass correlation coefficients (ICC). RESULTS: In general, group prevalences and means were higher on re-interview. Kappa estimates ranged from 0.15 to 0.84 among cases, and 0.26 to 0.87 among controls, with most estimates falling between 0.5 and 0.8. Moderate to almost perfect agreement (kappa) was observed for questions on crop work (0.47-0.70), crop type (0.56-0.82), pesticide application to tobacco (0.77), and farm residence (0.84). ICC estimates for continuous variables showed fair to substantial agreement (0.30 to 0.69 among cases, 0.38 to 0.69 among controls). Older cases, less educated cases, cases who lived on more than one farm, and cases with longer time intervals between interviews gave lower total agreement than similar groups of controls. CONCLUSIONS: Agreement estimates in this study are similar to those for other types of exposure information typically collected in epidemiologic studies. Nevertheless, a farm-by-farm method of exposure assessment may be preferable to an ever/never determination.

Agriculture↗

PubMed2001

Population-based case-control study of occupational exposure to electromagnetic fields and breast cancer.

PURPOSE: This population-based case-control study examined occupational exposure to electromagnetic fields in relation to female breast cancer incidence among 843 breast cancer cases and 773 controls. METHODS: Exposure was classified based on work in the two longest-held jobs, and indices of cumulative exposure to magnetic fields based on a measurement survey. RESULTS: Female breast cancer was not associated with employment as an office or industrial worker. For the total study population, cumulative exposure over the entire career, and in the past 0-10 and 10-20 years generally showed odds ratios (ORs) close to the null. Moderately elevated risks were found for intermediate but not high levels of cumulative exposure accumulated 20 or more years ago (OR = 1.5; 95% CI = 1.1-2.0). Associations were stronger for premenopausal women (OR = 1.7; 95% CI = 1.1-2.7) in the past 10-20 years, and those with estrogen-receptor positive (ER+) breast tumors (OR = 2.06; 95% CI = 1.1-4.0). No consistent dose-response patterns were observed. CONCLUSIONS: These findings give little support to the hypothesis that electromagnetic fields cause cancer of the female breast.

Adult↗

PubMed2001

Diagnostic radiation and the risk of multiple myeloma (United States).

OBJECTIVE: To evaluate the relationship between cumulative lifetime exposure to diagnostic radiation and the risk of multiple myeloma using data from a large, multi-center, population-based case-control study. METHODS: Study subjects included a total of 540 cases with newly diagnosed multiple myeloma and 1998 frequency-matched population controls living in three areas of the United States (Georgia, Michigan, New Jersey). Information on exposure to diagnostic X-rays was obtained by personal interview. RESULTS: No association was found between case-control status and the total number of reported diagnostic X-rays of any type (odds ratio (OR) for 20 or more compared to less than 5 X-rays = 0.9, 95% confidence interval (95% CI) = 0.7-1.2). There was no evidence of an excess risk of multiple myeloma among individuals who reported exposure to 10 or more diagnostic X-rays that impart a relatively high radiation dose to the bone marrow, as compared to individuals reporting no such exposures (OR 0.7, 95% CI 0.4-1.3). CONCLUSIONS: These data suggest that exposure to diagnostic X-rays has a negligible impact, if any, on risk of developing multiple myeloma.

Adult↗

PubMed2001

The effect of vaginal bleeding during pregnancy on preterm and small-for-gestational-age births: US National Maternal and Infant Health Survey, 1988.

We examined the effects of vaginal bleeding during pregnancy on preterm and small-for-gestational-age (SGA) births using data from the 1988 US National Maternal and Infant Health Survey. We examined the severity of vaginal bleeding and separated the preterm births into subsets by the degree of prematurity (< 32, 32-33, 34-36 weeks' gestation). We also evaluated associations stratified by race. Multiple logistic regression analysis showed that vaginal bleeding was associated with an increased risk of preterm birth, with a more pronounced elevated risk for preterm birth before 34 weeks' gestation and a notably stronger association for more severe bleeding that occurred in both the first and the second half of pregnancy. Odds ratios, but not risk differences, for birth before 34 weeks' gestation were greater for white women with vaginal bleeding than for black women. There was no association between vaginal bleeding during pregnancy and SGA births.

Female↗