Irva Hertz-Picciotto

Psychosocial Factors and Preterm Birth Among African American and White Women in Central North Carolina

Objectives. We assessed associations between psychosocial factors and preterm birth, stratified by race in a prospective cohort study.Methods. We surveyed 1898 women who used university and public health prenatal clinics regarding various psychosocial factors.Results. African Americans were at higher risk of preterm birth if they used distancing from problems as a coping mechanism or reported racial discrimination. Whites were at higher risk if they had high counts of negative life events or were not living with a partner. The association of pregnancy-related anxiety with preterm birth weakened when medical comorbidities were taken into account. No association with preterm birth was found for depression, general social support, or church attendance.Conclusions. Some associations between psychosocial variables and preterm birth differed by race.

Self-Reported Heavy Bleeding Associated With Uterine Leiomyomata

OBJECTIVE To characterize the relationship between self reported bleeding symptoms and uterine leiomyoma size and location. METHODS The leiomyoma status of a randomly selected sample of women aged 35–49 in the Washington, DC, area was determined using abdominal and transvaginal ultrasound to measure size and location of leiomyomata found at screening. Women were asked about symptoms of heavy bleeding (gushing-type bleeding, long menses, pad/ tampon use) in a telephone interview. Using multivariable regression, we examined the relationships between leiomyoma characteristics and heavy bleeding symptoms among 910 premenopausal women. RESULTS Women with leiomyomata (n = 596) were more likely to report gushing-type bleeding than women without leiomyomata; risk increased with leiomyoma size. Adjusted relative risks with 95% confidence intervals (CI) for women in each leiomyoma size category compared with the reference category (women without leiomyomata) were as follows: adjusted relative risk of 1.4 (95% CI 1.1, 1.9) for diffuse only, adjusted relative risk of 1.4 (95% CI 1.1, 1.8) for small leiomyomata (less than 2 cm), adjusted relative risk of 1.6 (95% CI 1.3, 2.0) for medium leiomyomata (2–5 cm), and adjusted relative risk of 1.9 (95% CI 1.5, 2.5) for large leiomyomata (greater than 5 cm). Reported use of eight or more pads/tampons on the heaviest days of menstrual bleeding increased with leiomyoma size, with a nearly 2.5-fold risk for women with large leiomyomata compared with women without leiomyomata (adjusted relative risk of 2.4; 95% CI 1.8, 3.1). Nonsubmucosal leiomyomata were associated with essentially the same increase in heavy bleeding as submuscosal leiomyomata of similar size. CONCLUSION Small leiomyomata were associated with increased risk of heavy bleeding, and risk increased with size. Contrary to published articles, nonsubmucosal leiomyomata were associated with heavy bleeding to the same extent as submucosal leiomyomata.

A case-control study of pesticides and fetal death due to congenital anomalies

We examined the association between late fetal death due to congenital anomalies (73 cases, 611 controls) and maternal residential proximity to pesticide applications in ten California counties. A statewide database of all applications of restricted pesticides was linked to maternal address to determine daily exposure status. We examined five pesticide chemical classes. The odds ratios from logistic regression models, adjusted for maternal age and county, showed a consistent pattern with respect to timing of exposure; the largest risks for fetal death due to congenital anomalies were from pesticide exposure during the 3rd–8th weeks of pregnancy. For exposure either in the square mile of the maternal residence or in one of the adjacent 8 square miles, odds ratios ranged from 1.4 (95% confidence interval = 0.8–2.4) for phosphates, carbamates, and endocrine disruptors to 2.2 (95% confidence interval = 1.3–3.9) for halogenated hydrocarbons. Similar odds ratios were observed when a more restrictive definition of nonexposure (not exposed to any of the five pesticide classes during the 3rd–8th weeks of pregnancy) was used. The odds ratios for all pesticide classes increased when exposure occurred within the same square mile of maternal residence.

Epidemiology and quantitative risk assessment: a bridge from science to policy.

Quantitative risk assessment provides formalized scientific input to regulatory agencies that set occupational and environmental standards for potentially toxic exposures. Current practice relies heavily on statistical extrapolation from high-dose animal studies. Human data obviate the need for interspecies extrapolation and reduce the range of high-to-low dose extrapolation. This paper proposes a framework for classifying individual epidemiologic studies as to their adequacy for use in dose-response extrapolation. The framework considers five criteria: (1) a stable positive association with an adverse health outcome; (2) high overall study quality; (3) no substantial confounding; (4) quantitative exposure assessment for individuals; (5) evidence of a dose-response relationship. With these criteria, studies can be categorized as (1) suitable to serve as a basis for extrapolation; (2) inadequate to be the basis for direct extrapolation but appropriate to use for evaluating the plausibility of animal-derived risk estimates; or (3) useful only for hazard identification, not for dose-response assessment. Methods for using studies in the first two categories are briefly described. The emphasis is not on establishing rigid rules, but rather on ensuring a consistent, reliable process that makes optimum use of available data.

Validity and efficiency of approximation methods for tied survival times in Cox regression

Survival-time studies sometimes do not yield distinct failure times. Several methods have been proposed to handle the resulting ties. The goal of this paper is to compare these methods. Simulations were conducted, in which failure times were generated for a two-sample problem with an exponential hazard, a constant hazard ratio, and no censoring. Failure times were grouped to produce heavy, moderate, and light ties, corresponding to a mean of 10.0, 5.0, and 2.5 failures per interval. Cox proportional hazards models were fit using each of three approximations for handling ties with each interval size for sample sizes of n = 25, 50, 250, and 500 in each group. The Breslow (1974, Biometrics 30, 89-99) approximation tends to underestimate the true beta, while the Kalbfleisch-Prentice (1973, Biometrika 60, 267-279) approximation tends to overestimate beta. As the ties become heavier, the bias of these approximations increases. The Efron (1977, Journal of the American Statistical Association 72, 557-565) approximation performs far better than the other two, particularly with moderate or heavy ties; even with n = 25 in each group, the bias is under 2%, and for sample sizes larger than 50 per group, it is less than 1%. Except for the heaviest ties in the smallest sample, confidence interval coverage for all three estimators fell in the range of 94-96%. However, the tail probabilities were asymmetric with the Breslow and Kalbfleisch-Prentice formulas; using the Efron approximation, they were closer to the nominal 2.5%. Although the Breslow approximation is the default in many standard software packages, the Efron method for handling ties is to be preferred, particularly when the sample size is small either from the outset or due to heavy censoring.

The association of urinary incontinence with poor self-rated health

OBJECTIVES: To assess whether urinary incontinence (UI) and its severity are associated with poor self‐rated health in a national sample of community‐living older adults and whether this relationship persists after controlling for confounding attributable to functional status, comorbidity, and demographic factors.

Risk of stillbirth from occupational and residential exposures.

OBJECTIVES: To analyse the risk of stillbirth from 12 residential and occupational maternal exposures during pregnancy. METHODS: Stillbirths and neonatal deaths in 1984 within 24 hours of birth from 10 California counties were identified from death certificates. Controls were randomly selected from live births born in 1984 and frequency matched to cases by maternal age and county. Data sources included vital statistics and a self-administered postal questionnaire. Logistic regression and proportional hazards modelling were performed; the proportional hazards considered the truncated opportunity for exposure among cases. Special focus was given to two cause of deaths groups: congenital anomalies (12% of deaths) and complications of the placenta, cord, and membranes (37% of deaths). RESULTS: Occupational exposure to pesticides during the first two months of gestation was positively associated with stillbirths due to congenital anomalies (odds ratio (OR) 2.4, 95% confidence interval (95% CI) 1.0 to 5.9), and during the first and second trimesters with stillbirths due to all causes of death (risk ratios (RR) 1.3-1.4, 95% CI 1.0 to 1.7) and stillbirths due to complications of the placenta, cord, and membranes (RR 1.6-1.7, 95% CI 1.1 to 2.3). Occupational exposure to video display terminals in the third trimester was found to have a modest inverse association with stillbirths (RR 0.7, 95% CI 0.6, 0.9). Home pesticide exposure was positively associated with stillbirths due to congenital anomalies (OR 1.7, 95% CI 1.0 to 2.9). CONCLUSIONS: Occupational exposure to pesticides, especially during early pregnancy, had a clear positive association with stillbirths regardless of cause of death. Methodologically, this study of stillbirths is unique in its analysis of specific causes of death and use of time specific exposure windows.

Residential pesticide exposure and neuroblastoma.

Neuroblastoma is the most common neoplasm in children under 1 year of age. We examined the relation between residential exposure to pesticides and neuroblastoma, using data from a case-control study of risk factors for neuroblastoma. Incident cases of neuroblastoma (N = 538) were identified through the Pediatric Oncology Group and the Children’s Cancer Group. One age-matched control was identified for each case by random digit dialing. Telephone interviews with each parent collected information on residential exposure to pesticides. Pesticide use in both the home and garden were modestly associated with neuroblastoma [odds ratio (OR) = 1.6 (95% confidence interval [95% CI] = 1.0–2.3, and OR = 1.7 (95% CI = 0.9–2.1), respectively]. Compared with infants [OR = 1.0 (95% CI = 0.6–2.0)], stronger associations were found for garden pesticides in children diagnosed after 1 year of age [OR = 2.2 (95% CI = 1.3–3.6)], which suggests that pesticides may act through a mechanism more common for neuroblastomas in older children. There was no evidence of differential pesticide effects in subgroups of neuroblastoma defined by MYCN oncogene amplification or tumor stage.

Effect of Organization-Level Variables on Differential Employee Participation in 10 Federal Worksite Health Promotion Programs

Guided by a conceptual model, the authors used both qualitative data (e.g., individual interviews, focus groups) and quantitative data from an employee survey (N = 3,388) m 10 federal agencies to investigate whether organization context and implementation process affected participation in worksite health promotion and disease prevention (HPDP) activities among demographic subgroups. Overall, employees on average participated in fewer than two agency-supported health-related activities per year (17% in fitness, 40% inhealth risk assessment activities). Employees participated more where coworkers endorsed such programs. Minority employees and employees in lower level positions were more likely to participate in fitness activities when organizations had a more comprehensive program structure, engaged in more marketing strategies, gave time off to employees to participate, or had on-site facilities. Management support for the program was related to participation by employees who were male, white, and had upper level positions. The data supported the proposed model; also confirmed was two predicted relationships between model constructs, which provided a better understanding of differential participation by employee groups.

Case-Cohort Analysis of Agricultural Pesticide Applications near Maternal Residence and Selected Causes of Fetal Death

The potential association between fetal death and residential proximity to agricultural pesticide applications was examined in 10 California counties for 1984. A case-cohort analysis utilized 319 cases of selected causes of fetal death other than congenital anomalies and 611 non-cases. A statewide database of all applications of restricted pesticides was linked to maternal address; residential proximity within 1 mile (1.6 km) provided a surrogate for daily exposure. Pesticides were grouped by chemical class and mechanism of acetylcholinesterase inhibition. Multivariate proportional hazards models using time-dependent exposure variables were fit for each pesticide grouping. Overall, pesticides showed no strong association with fetal death. Slightly elevated risks were observed for women who resided near applications of halogenated hydrocarbons, carbamates, estrogenic pesticides, and carbamate acetylcholinesterase inhibitors during the second trimester, with hazard ratios of 1.3 (95% confidence interval (CI): 1.0, 1.8), 1.3 (95% CI: 1.0, 1.8), 1.4 (95% CI: 0.8, 2.5), and 1.3 (95% CI: 1.0, 1.8), respectively. In a month-by-month analysis, elevated risks were observed when exposure occurred during gestational months 3 and 4 for carbamates and carbamate inhibitors and during months 4 and 5 for halogenated hydrocarbons. Since previous studies have relied on personal recall of exposure, major strengths of this study were the objective source for environmental pesticide exposure assessment and the use of data on the timing of exposure.