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Biomedical subjects

D A Savitz

Publications and source records attributed to D A Savitz.

At least 199 records · Page 11Linked to original sources
PubMed1990

Maternal employment and reproductive risk factors.

Studies of reproductive hazards in the workplace must address potential biases related to selection for employment. The National Natality Survey, a probability sample of live births to married women in 1980, was used to examine the relation between female employment during pregnancy and factors that might affect reproductive outcome by analyzing the 5,927 women with complete occupational data. Demographic and behavioral attributes as well as reproductive history were compared for the 3,712 women employed and the 2,215 women not employed during pregnancy. Employed mothers were of more optimal reproductive age, were more highly educated, had higher incomes, began prenatal care earlier, had greater weight gain during pregnancy, and were slightly less likely to be heavy smokers. Employed women had markedly fewer previous births and less favorable reproductive histories (more stillbirths, miscarriages, and induced abortions) than unemployed women, controlling for gravidity. Full- and part-time workers were similar with regard to demographic and behavioral characteristics, but part-time workers had higher parity. Differences were noted by employment sector: professional women had especially favorable demographic and behavioral traits, and women employed as operatives and service workers were less advantaged. These results indicate that substantial differences in pregnancy-related risk factors exist in relation to employment, with working women generally having more favorable demographic and behavioral characteristics and less favorable reproductive histories. This pattern could produce selection bias in studies of work and reproductive health, and it encourages the restriction of comparison groups to other employed women, with a need to consider heterogeneity among working women as well.

Adult↗
PubMed1990

Scientific standards of criticism: a reaction to "Scientific standards in epidemiologic studies of the menace of daily life," by A.R. Feinstein.

Feinstein's criticism of epidemiology are summarized and evaluated. His major premises appear to be that methodologic errors inevitably result in false positive associations, that epidemiologists are complacent about methodology, and that epidemiologists encourage overinterpretation of epidemiologic data by the public. We challenge these premises and discuss a number of technical errors that underlie Feinstein's writings: he generally ignores the tendency of nondifferential exposure misclassification to dilute associations; he inappropriately interchanges measure of disease occurrence, which leads him to erroneous assertions regarding differences among studies; and he asserts that absence of a dose-response gradient precludes causality, despite the fact that causal effects need not follow a monotonic dose-response curve over the entire range of exposure. We also challenge his assertions that contradictory results necessarily indicate poor study methods and that prior beliefs of the data collectors inevitably affect study results in ways not apparent in the study methods. Feinstein's approach to the use of epidemiology in policy formulation ignores the need to weigh all evidence and distinguish important from unimportant biases. We illustrate this point by documenting how the use of Feinstein's "scientific standards" in evaluating the evidence linking aspirin to Reye's syndrome would have led to costly errors in medical practice.

Aspirin↗
PubMed1990

Barrier and spermicidal contraceptive methods and risk of invasive cervical cancer.

The effects of barrier and spermicidal methods of contraception on cervical cancer risk were examined by studying 479 cases of histologically confirmed invasive cervical cancer cases and 788 random digit dialing controls. In addition to a detailed history of contraceptive practices, information was available on numerous potential confounders, including demographic characteristics, sexual behavior, reproductive factors, Pap smear screening history, and smoking. After adjustment for relevant confounders, diaphragm and condom use were found not to be significantly associated with risk of cervical cancer. Although there was a small reduction in risk (OR = 0.8) associated with long-term use (5+ years) of the diaphragm, the effect appeared to relate to concomitant spermicide use, since there was evidence of further decreases in risk for women using spermicides alone for extended periods (OR = 0.7 for 5+ years). Effects were only seen among subjects of higher income and education levels, suggesting that patterns of usage may be important. The potential ability of spermicides to reduce cervical cancer risk by neutralizing viral agents warrants further attention.

Adult↗
PubMed1990

Mortality from brain cancer and leukaemia among electrical workers.

The relation of brain cancer and mortality from leukaemia to electrical occupations was investigated in a case-control study based on all deaths in 1985 and 1986 in the 16 states in the United States that report occupational data from death certificates to the national vital statistics registry. The case series comprised all 2173 men who died of primary brain cancer (International Classification of Diseases-9 ((ICD-9) code 191) and all 3400 who died of leukaemia (ICD-9 codes 204-208). Each was matched with 10 controls who died of other causes in the same year. Men employed in any electrical occupation had age race adjusted odds ratios (ORs) of 1.4 (95% confidence interval (CI) 1.1-1.7) for brain cancer and 1.0 (95% CI 0.8-1.2) for leukaemia, compared with men in all other occupations. Brain cancer odds ratios were larger for electrical engineers and technicians (OR 2.7, 95% CI 2.1-3.4), telephone workers (OR 1.6, 95% CI 1.1-2.4), electric power workers (OR 1.7, 95% CI 1.1-2.7), and electrical workers in manufacturing industries (OR 2.1, 95% CI 1.3-3.4). There was some evidence of excess leukaemia among the same groups (ORs of 1.1-1.5) despite absence of an association for all electrical workers. The excess of deaths from brain cancer was concentrated among men aged 65 or older, whereas leukaemia was associated with electrical work only among younger decedents and those with acute lymphocytic leukaemia. These results from a large and geographically diverse population corroborate reports of increased mortality from brain cancer among electrical workers, but gives only limited support to suggestions of excess deaths from leukaemia.

Age Factors↗
PubMed1990

Parental occupation and childhood cancer: review of epidemiologic studies.

Parental occupational exposures might affect childhood cancer in the offspring through genetic changes in the ovum or sperm or through transplacental carcinogenesis. The 24 published epidemiologic studies of this association have all used case-control designs, with controls generally selected from birth certificates or from general population sampling. Occupational exposures were inferred from job titles on birth certificates or through interviews. A large number of occupation-cancer associations have been reported, many of which were not addressed or not confirmed in other studies. Several associations have been found with consistency: paternal exposures in hydrocarbon-associated occupations, the petroleum and chemical industries, and especially paint exposures have been associated with brain cancer; paint exposures have also been linked to leukemias. Maternal exposures have received much less attention, but studies have yielded strongly suggestive results linking a variety of occupational exposures to leukemia and brain cancer. The primary limitations in this literature are the inaccuracy inherent in assigning exposure based on job title alone and imprecision due to limited study size. Although no etiologic associations have been firmly established by these studies, the public health concerns and suggestive data warrant continued research.

Adult↗
PubMed1989

An epidemiologic study of contraception and preeclampsia.

The primary hypothesis of this study was that contraceptive methods that prevent exposure to sperm and seminal fluid (condoms, diaphragms, spermicides, withdrawal) are associated with an increased risk of developing preeclampsia during the subsequent pregnancy. A case-control study was conducted comparing the contraceptive and reproductive histories of 110 primiparous women with preeclampsia with 115 pregnant women without preeclampsia, aged 15 to 35 years, who gave birth at North Carolina Memorial Hospital, Chapel Hill, between 1984 and 1987. Controls were frequency matched to cases by age, race, and distance from the hospital. Unconditional logistic regression analysis indicated a 2.37-fold (95% confidence interval, 1.01 to 5.58) increased risk of preeclampsia for users of contraceptives that prevent exposure to sperm. A dose-response gradient was observed, with increasing risk of preeclampsia for those with fewer episodes of sperm exposure. These results were supportive of the hypothesis that birth control methods that prevent sperm exposure may play a role in the etiology of preeclampsia.

Adolescent↗
PubMed1989

Estimating and correcting for confounder misclassification.

Confounder misclassification is as pervasive a problem in epidemiologic studies as misclassification of the primary exposure variables. Adjustment using imperfectly classified confounders has been shown to remove only part of the confounding effect of that variable, most important when studying an exposure postulated to have a modest effect in the presence of a strong confounder. The Per Cent Adjustment (amount of confounding bias removed using the misclassified measure relative to the total confounding bias present) is derived for several case-control scenarios, and is found to have a stable relation to the sensitivity and specificity of confounder classification. Figures are provided for estimation of the completely adjusted odds ratio given the results from the misclassified proxy and an estimate of the extent of misclassification. This offers a method for quantitative assessment of the impact of residual confounding that results from confounder misclassification, illustrated with studies of coffee consumption and bladder cancer in the presence of confounding by cigarette smoking.

Classification↗
PubMed1989

Effect of parents' occupational exposures on risk of stillbirth, preterm delivery, and small-for-gestational-age infants.

Epidemiologic research on the effects of parental occupational exposures on fetal development has been limited. The National Natality and Fetal Mortality surveys obtained applicable data on probability samples of live births and fetal deaths which occurred in the US in 1980 among married women. Analyses were conducted for case groups of stillbirths (2,096 mothers, 3,170 fathers), preterm deliveries (less than 37 weeks completed gestation) (363 mothers, 552 fathers), and small-for-gestational-age infants (218 mothers, 371 fathers) compared with controls. Occupational exposures were defined by industry of employment and by imputed exposures based on a job-exposure linkage system. For stillbirth, maternal work in the rubber, plastics, and synthetics industry (odds ratio (OR) = 1.8, 95% confidence interval (Cl) 0.8-4.0) and lead exposure (OR = 1.6, 95% Cl 0.8-3.1), and paternal employment in the textile industry (OR = 1.9, 95% Cl 1.2-2.9), had the largest odds ratios. Preterm birth was most strongly associated with maternal lead exposure (OR = 2.3, 95% Cl 0.7-7.0), corroborating previous findings. Twofold increased risk of preterm delivery was found with paternal employment in the glass, clay, and stone; textile; and mining industries. Paternal exposures to x-rays and polyvinyl alcohol were associated with 1.5-fold increase in risk. The occupation of the mother was not associated with delivery of a small-for-gestational-age infant, in contrast to paternal employment in the art (OR = 2.6, 95% Cl 1.2-5.6) and textile industries (OR = 2.5, 95% Cl 1.3-4.7). Several toxic agents were associated with risk elevation of 1.3 or greater for fathers, most notably benzene (OR = 1.5, 95% Cl 1.1-2.3). In spite of limitations in the exposure data, the size of the exposed populations, and possible confounding, the results in this study encourage further evaluation of the effects of maternal exposure to lead and possibly solvents, as well as paternal exposure in the textile industry and to x-rays and benzene.

Female↗
PubMed1989

Male infertility in inflammatory bowel disease.

We examined fertility in men with inflammatory bowel disease (IBD) to determine whether the reported deficit in pregnancies in their spouses was due to reduced reproductive capacity. The cases were 106 men with Crohn's disease and 62 with ulcerative colitis drawn from the rosters of North Carolina chapters of the National Foundation for Ileitis and Colitis. The 140 normal controls were neighbors identified by the cases. There were 186 pregnancies among the spouses of men with Crohn's disease, 110 among the ulcerative colitis group, and 300 among the controls. The mean number of pregnancies among the Crohn's disease patients (1.75 +/- 0.12) was significantly lower than the number for controls (2.14 +/- 0.11), p less than 0.02. The reduction in the mean number of pregnancies among patients with ulcerative colitis (1.77 +/- 0.18) was not significantly different from controls (p less than 0.07). Analysis of waiting time to conception showed that fecundability (the probability of pregnancy in a menstrual cycle) was not different in spouses of IBD patients and controls. We conclude that the overall reproductive capacity of men with IBD is not markedly diminished.

Adult↗
PubMed1989

Association of childhood cancer with residential traffic density.

Data from a recently completed case-referent study of childhood cancer were used to explore a possible role of environmental exposures from traffic exhaust. The street addresses of 328 cancer patients and 262 population-based referents were used to assign traffic density (vehicles per day) as a marker of potential exposure to motor vehicle exhaust. An odds ratio of 1.7 [95% confidence interval (95% CI) 1.0-2.8] was found for the total number of childhood cancers and 2.1 (95% CI 1.1-4.0) for leukemias in a contrast of high and low traffic density addresses (greater than or equal to 500 versus less than 500 vehicles per day). Stronger associations were found with a traffic density cutoff score of greater than or equal to 10,000 vehicles per day, with imprecise odds ratios of 3.1 (95% CI 1.2-8.0) and 4.7 (95% CI 1.6-13.5) for the total number of cancers and leukemias, respectively. Adjustment for suspected risk factors for childhood cancer did not substantially change these results. Though the results are inconclusive, the identified association warrants further evaluation.

Adolescent↗
PubMed1988

Infant feeding and childhood cancer.

A case-control study was used to assess whether inadequate exposure to the immunological benefits of human milk may affect infants' response to infection and make them more susceptible to childhood malignancies. 201 Denver children with cancer diagnosed at 1.5-15 years of age were compared with 181 controls, who were selected to be similar to cases for age, sex, and area of residence. Infant feeding categories were: breast feeding (BF) greater than 6 months; BF less than or equal to 6 months; and artificial feeding (AF, or exclusive non-human milk feeding). Compared with BF greater than 6 months, a raised risk for total cancers was found in both BF less than or equal to 6 month and AF groups. This increased risk was largely due to an increased incidence of lymphoma (n = 26).

Adolescent↗
PubMed1988

Case-control study of childhood cancer and exposure to 60-Hz magnetic fields.

Concern with health effects of extremely low frequency magnetic fields has been raised by epidemiologic studies of childhood cancer in relation to proximity to electric power distribution lines. This case-control study was designed to assess the relation between residential exposure to magnetic fields and the development of childhood cancer. Eligible cases consisted of all 356 residents of the five-county 1970 Denver, Colorado Standard Metropolitan Statistical Area aged 0-14 years who were diagnosed with any form of cancer between 1976 and 1983. Controls were selected by random digit dialing to approximate the case distribution by age, sex, and telephone exchange area. Exposure was characterized through in-home electric and magnetic field measurements under low and high power use conditions and wire configuration codes, a surrogate measure of long-term magnetic field levels. Measured magnetic fields under low power use conditions had a modest association with cancer incidence; a cutoff score of 2.0 milligauss resulted in an odds ratio of 1.4 (95% confidence interval (CI) = 0.6-2.9) for total cancers and somewhat larger odds ratios (ORs) for leukemias (OR = 1.9), lymphomas (OR = 2.2), and soft tissue sarcomas (OR = 3.3). Neither magnetic fields (OR = 1.0) nor electric fields (OR = 0.9) under high power use conditions were related to total cancers. Wire codes associated with higher magnetic fields were more common among case than control homes. The odds ratio to contrast very high and high to very low, low, and buried wire codes was 1.5 (95% CI = 1.0-2.3) for total cases, with consistency across cancer subgroups except for brain cancer (OR = 2.0) and lymphomas (OR = 0.8). Contrasts of very high to buried wire code homes produced larger, less precise odds ratios of 2.3 for total cases, 2.9 for leukemias, and 3.3 for lymphomas. Adjusted estimates for measured fields and wire codes did not differ from crude results, indicating an absence of confounding. Limitations to the study are nonresponse (especially for field measurements), differential mobility of cases and controls, and a presumably nondifferential exposure misclassification from the use of imperfect surrogates for long-term magnetic field exposure history. In spite of these concerns, the results encourage further examination of the carcinogenic potential from this form of nonionizing radiation.

Adolescent↗
PubMed1988

Reduced risk of IDDM among breast-fed children. The Colorado IDDM Registry.

The hypothesis that breast-feeding can provide protection against the development of insulin-dependent diabetes mellitus (IDDM) and would, therefore, be less common among subjects with IDDM was tested with a retrospective design. Cases (n = 268) were selected from the Colorado IDDM Registry and the Barbara Davis Center for Childhood Diabetes (Denver, CO). Two control groups were recruited, one from physicians' practices throughout Colorado (n = 291) and the second through random-digit dialing from the Denver area (n = 188). Cases were less likely to have been breast-fed than controls after adjustment for birth year, maternal age, maternal education, family income, race, and sex [adjusted odds ratio (OR) = 0.70; 95% confidence interval (CI) = 0.50-0.97]. This finding was consistent for both control groups and by birth-year intervals. A greater decrease in risk of IDDM was seen among subjects who had been breast-fed to an older age (for breast-feeding duration of greater than or equal to 12 mo, adjusted OR = 0.54, 95% CI = 0.27-1.08). The amount of IDDM that might be explained by breast-feeding habits (population percentage attributable risk) ranged from 2 to 26%, varying according to the breast-feeding prevalence reported in other studies. Replication of this work in different populations, controlled for the strong secular trends in breast-feeding habits, is critical before the hypothesis of protection is accepted.

Breast Feeding↗
PubMed1987

Childhood cancer in the Denver metropolitan area 1976-1983.

Incidence rates for childhood cancers (ages 0-14 years) were produced for the Denver Standard Metropolitan Statistical Area for the period 1976-1983. Some unique features of the Denver area, especially the unusually high background levels of ionizing radiation, warrant comparisons with rates generated from other regions. A total of 348 childhood cancers were identified in white (including Spanish surname) and black children, with the 200 cancers among males resulting in higher rates than for females (148 cases) for total cancers and selected major cancer types (leukemias, glial brain cancers, and non-Hodgkin's lymphomas). Compared with other geographic areas, Denver rates were very similar, with no marked excesses or deficits except for an increase in male endocrine cancers. Rates for Spanish surname children were very similar to the rates for other whites.

Adolescent↗
PubMed1987

Epidemiology of cervical cancer by cell type.

A multicenter case-control study of 481 invasive cervical cancer patients and 801 population controls enabled comparison of risk factors for squamous cell tumors (n = 418), adenosquamous cancers (n = 23), and adenocarcinomas (n = 40). The epidemiology of the squamous cell tumors resembled that found in other studies, with the major risk factors being absence of Pap smear screening (relative risk = 3.6 to 4.8 for those not screened within 5 yr), multiple sexual partners (relative risk = 2.9 for over ten partners), and history of genital infections or sores (relative risk = 2.3). Although based on small numbers, adenosquamous tumors appeared to share some of these risk factors, notably number of sexual partners, years since last Pap smear, and level of education. Adenocarcinomas were not similarly affected, although sexual practices were marginally predictive. Obesity increased the risk of adenocarcinoma, but no other similarities to endometrial adenocarcinoma were observed. Smoking was a significant predictor of squamous cell tumors but did not affect adenocarcinomas. Extended use of oral contraceptives was a risk factor for all tumor types, especially adenocarcinoma, and a familial tendency to cervical cancer was also observed for all cell types.

Adenocarcinoma↗