TABLE 1.
Summary of Study Characteristics
| Study Characteristic | Columbia Center for Children's Environmental Health (CCCEH) | Center for Health Assessment of Mothers and Children of Salinas (CHAMACOS) | Mt. Sinai Children's Environmental Health Cohort Study | |
|---|---|---|---|---|
| Author (citation) | Rauh et al., 2006 | Eskenazi et al., 2007 | Young et al., 2005 | Engel et al., 2007 |
| Location | New York City, NY, USA | Salinas Valley, CA, USA | New York City, NY, USA | |
| Study design | Cohort | Cohort | Cohort | |
| Enrollment years | 1998–2002 | 1999–2000 | 1998–2001 | |
| Maternal eligibility | Pregnant nonsmokers, self-identified as black or Dominican, registered at the OB-GYN clinics at NY Presbyterian Medical Center and Harlem Hospital prior to 20 weeks gestation, 18–35 years old, free from diabetes and hypertension, no diagnosis of HIV, did not use drugs, and lived in the area for ≥1 year. | Pregnant Spanish or English speaking women, receiving prenatal care at one of six community clinics that served farm workers with plans to deliver at Natividad Medical Center, <20 weeks gestation at enrollment, ≥18 years old, eligible for Medi-Cal (California's Medicaid health care program). | Pregnant, primiparous, singleton pregnancies, receiving prenatal care from Mount Sinai Hospital, no underlying health conditions that might predispose to giving birth to high risk infants | |
| Study sizea | 254 | 447 | 381 | 311 |
| Outcome measurements (assessment tool)b | BSID:MDI; BSID:PDI; CBCL |
BSID:MDI; BSID:PDI; CBCL |
BNBAS | BNBAS |
| Outcome variable format |
BSID: Continuous and categorical measurement of BSID:MDI and BSID:PDI (low: ≤85; high >85) CBCL: Categorical, using 98th percentile of the national normative sample in each domain as cutoff |
BSID: Continuous measurement of BSID:MDI and BSID:PDI. CBCL: Categorical, using 93rd percentile of the national normative sample in each domain as the cutoff |
BNBAS: Continuous measure of BNBAS domains. Categorical measure of abnormal reflexes (>3 vs. ≤3) | BNBAS: Continuous measure of BNBAS domains. |
| Timing of outcome assessment | BSID: Age 12, 24, 36 months CBCL: Age 36 months |
BSID: Age 6, 12, 24 months CBCL: Age 24 months |
BNBAS: Age ≤2 months | BNBAS: Within ≤5 days of delivery |
| Testing conditions | “… each child was tested under controlled conditions in the study office by a trained bilingual research assistant, checked for reliability. Five different testers conducted a total of 1101 BSID-II assessments over the course of the 3-year study period. Every effort was made to maximize reliability in scoring by using standardized training procedures and regular quality control. Interrater reliability for the 24-month BSID-II assessments was r = 0.92, on the basis of double-scoring of a random 5% of the sample.” | “Both [BSID] scales were administered in Spanish and/or English by psychometricians blind to exposure. Psychometricians were trained using standardized protocols and were supervised for quality assurance by a clinical neuropsychologist. Assessments were performed in a private room at the CHAMACOS research office or in a recreation vehicle (RV) modified to be a mobile testing facility.” | “The BNBAS was administered once to each infant and in accordance with the BNBAS protocol, by four examiners trained to reliability by a BNBAS certified trainer. Examiners were blind to the infant's exposure status. Approximately 30% of the assessments included in the final sample were completed prior to discharge from the hospital; the remainder was performed at the CHAMACOS research office or in the participant's home. Assessments were performed away from the mother in a private room with low-level light and noise control.” |
“The BNBAS was administered before hospital discharge (n =311) by one of four examiners. Examiners were either trained and certified by the Brazelton Institute or trained by a certified examiner. Examinations took place in a quiet, semidarkened, warm room adjacent to the neonatal nursery, or in the mother's private room. The BNBAS was not administered if the infant was admitted to the Neonatal Intensive Care Unit (n = 21); if the infant was delivered and discharged over a weekend (n = 43); if the parent refused (n = 5); if the infant was not testable (n = 2); or if study personnel were unavailable (n = 22).” |
| Exposure measurement (Chemical/Metabolitec & biological specimen) | CPF in umbilical cord bloodd | TCPy in maternal urine DEPs & DAPs in maternal and child urine |
DEPs & DAPs in maternal urine | DEPs & DAPs in maternal urine |
| Timing of exposure assessment (approx.) | At delivery | During pregnancy (maternal prenatal): 14 and 26 weeks gestation; an average of these two measures was calculated Postnatal (child): age 6, 12, and 24 months |
During pregnancy (maternal prenatal): 14 and 26 weeks gestation; an average of these two measures was calculated Post-delivery (maternal): 7 days postpartum |
During pregnancy (maternal prenatal): 31 weeks gestation |
| Exposure variable format for analysis | Categorical: >6.17 pg/g vs. ≤6.17pg/g | Continuous: (nmol/L – log10) Categorical: (<LOD (ref), below median, above median detectable level) |
Continuous: (nmol/L – logio) | Continuous: (nmol/L – logio) |
| Detection limit of chemical or metabolite | LOD = 0.5–1 pg/g; 80 samples below LOD Median CPF levels not provided. |
TCPy detected in 91% of prenatal maternal samples (averaged). Prenatal (maternal): Median TCPy = 3.5 ug/L Percent with DEPs and DAPs detected not provided. Geometric means: Maternal (prenatal) (average) DEPs = 18.1 nmol/L, DAPs = 114.9nmol/L Geometric means: Child (postnatal) 6 mos. DEPs = 10.6 nmol/L, 12 mos. DEPs = 15.2 nmol/L, 24 mos. DEPs = 10.5 nmol/L, 6 mos. DAPs = 45.5 nmol/L, 12 mos. DAPs = 59.5 nmol/L, 24 mos. DAPs = 70.9 nmol/L, |
DEPs and DAPs detected in 100%of prenatal samples (averaged) Prenatal (maternal): Median DEPs = 21 nmol/L Median DAPs = 132 nmol/L |
DEPs detected in 89% of samples; DAPs detected 97% of samples Prenatal (maternal): Median DEPs = 24.7 nm/L Median DAPs = 82.0 nm/L |
| Information Obtained from Questionnaire / Interview | Demographic characteristics, home characteristics, lifetime residential history, history of active/passive smoking, occupational history, maternal education, income level, alcohol/drug use during pregnancy, history of residential pesticide use. Test of Nonverbal Intelligence, Home Observation for Measurement of the Environment (HOME) |
Family demographics, work histories of household members, maternal behaviors (smoking, alcohol, drug use), maternal medical history (previous pregnancies) Peabody Picture Vocabulary Test (PPVT), Center for Epidemiologic Studies Depression Scale, Home Observation for Measurement of the Environment (HOME) |
Family demographics, work histories of household members, maternal behaviors (smoking, alcohol, drug use), maternal medical history (previous pregnancies) | Environmental exposures, sociodemographic information, medical history, lifestyle factors. |
| Method of Assessing Confounding | “Covariates were included in models as possible confounders if they (1) had a significant association with level of pesticide exposure and any measure of developmental outcomes in this sample, (2) altered the estimate of chlorpyrifos effect by ≥10%, or (3) had been identified as confounders in comparable studies.” | “Covariates were selected for these analyses if they were related to conditions of testing; related to neurodevelopment in the literature; and associated (p < 0.10) with most outcomes; or consistently related to neurodevelopment in the literature even if not in our data.” “In addition to the variables we included, we examined the potential confounding effects of several other variables suggested by the literature but they did not markedly alter the observed associations.” “For simplicity, the same set of covariates was used for CBCL models with three exceptions: maternal depression, found to be important (p < 0.10), was added, and psychometrician and assessment location were dropped, because scores were based on maternal report.” |
“Covariates were initially selected based on their predictive value of BNBAS performance reported in the literature.” “Covariates from this (initial) list were selected for final regression models if they were related to each of the seven BNBAS cluster scores, unadjusted for other variables (p < 0.15).” |
“Backward elimination was used to arrive at the final adjusted models. Covariates were eliminated if their exclusion caused less than a 20 percent change in the beta coefficient of the full model.” |
| Maternal Demographic Characteristics | ||||
| Race/ethnicity | ||||
| White | 20.3% | |||
| Black | ∼42%f | 27.3% | ||
| Latina | ∼100% | ∼100% | 51.1% | |
| Dominican | ∼58%f | - | ||
| Other | 1.3% | |||
| Maternal age | mean years ± SD | Age group % | mean years ± SD | Age group % |
| 24.6 ± 4.9f | 18–24 44.5% | 26 ±5 | <20 35.7 | |
| 25–29 31.1% | 20–24 32.5 | |||
| 30–34 16.3% | 25–29 12.2 | |||
| ≥ 35 8.1% | 30–34 15.1 | |||
| ≥35 4.5 | ||||
| Did not complete high school | 34.6%* | 80.5% | 81.4% | 31.5% |
| Married/living as married/living with infant's father | 17%* | 81.9% | 81.1% | 52.4% |
a
Number of observations in analyses may be less, depending on the infant's attained age at the time of testing, availability of exposure data, testing data, and covariate data
b
Outcome assessment tool: BNBAS: Brazelton Neonatal Behavioral Assessment Scale; BSI-MDI: Bayley Scales of Infant Development-Mental Development Index; BSI-PDI: Bayley Scales of Infant Development – Psychomotor Development Index; CBCL: Child Behavior Checklist
c
Chemicals/Metabolites: DAPs = total dialkyl phosphates; DEPs = diethylphosphate; CPF: chlorpyrifos; TCPy = 3,5,6-trichloro–2-pyridionol
d
Maternal blood was used when cord blood was unavailable.
e
Maternal smoking during pregnancy or maternal residence with a smoker during pregnancy.