Table 1.
Characteristics of New Bedford Cohort (NBC) participants who were included in the main analysis group1 and those who were excluded.
| Descriptive Characteristic | Main analysis group, n=373 | Excluded group, n=415 | |||||
|---|---|---|---|---|---|---|---|
|
| |||||||
| Working Memory Measures3 | n(%) | Mean (SD) | Range | n(%) | Mean (SD) | Range | p-value2 |
| Verbal Working Memory | 373 | 9.0 (2.7) | 1–16 | 155 | 8.3 (2.9) | 1–17 | 0.01* |
| Symbolic Working Memory | 373 | 9.8 (2.8) | 1–19 | 154 | 9.2 (2.6) | 1–14 | 0.02* |
| Working Memory Index | 373 | 96.6 (13.2) | 55–142 | 154 | 93.1 (13.1) | 60–128 | 0.01* |
| Exposure Measures 4,5 | |||||||
| Cord serum DDE (ng/g) | 373 | 0.6 (1.2) | 0.02–14.9 | 378 | 0.4 (0.4) | 0–4.2 | < 0.01* |
| Cord serum HCB (ng/g) | 373 | 0.03 (0.02) | 0–0.1 | 378 | 0.03 (0.05) | 0–0.7 | 0.1 |
| Cord serum ΣPCB4 (ng/g) | 373 | 0.3 (0.3) | 0.01–4.4 | 378 | 0.2 (0.2) | 0.01–1.9 | 0.05 |
| Cord blood Pb (μg/dL) | 373 | 1.4 (0.9) | 0–9.4 | 375 | 1.7 (1.7) | 0–17.4 | < 0.01* |
| Cord blood Mn (μg/dL) | 373 | 4.2 (1.6) | 0.7–14.6 | 335 | 4.3 (2.0) | 0.2–22.1 | 0.6 |
| Covariate Measures 6 | |||||||
| Child Characteristics | |||||||
| Race/Ethnicity | 0.09 | ||||||
| Non-Hispanic White | 263 (70.5) | 268 (64.6) | |||||
| Hispanic | 33 (8.8) | 56 (13.5) | |||||
| Other | 77 (20.6) | 89 (21.4) | |||||
| Missing | 0 | 2 (0.5) | |||||
| Sex | 0.05 | ||||||
| Male | 179 (48.0) | 229 (55.2) | |||||
| Female | 194 (52.0) | 186 (44.8) | |||||
| Age at Exam | 373 | 15.5 (0.6) | 14.4–17.8 | 155 | 15.7 (0.7) | 13.9–17.9 | < 0.01* |
| Home Score | 373 | 43.9 (6.3) | 21–56 | 118 | 42.7 (6.0) | 27–53 | 0.07 |
| Year of Birth | |||||||
| 1993–1994 | 100 (26.8) | 159 (38.3) | < 0.01* | ||||
| 1995–1996 | 153 (41.0) | 147 (35.4) | |||||
| 1997–1998 | 120 (32.2) | 109 (26.3) | |||||
| Maternal Characteristics | |||||||
| Marital status at birth | < 0.01* | ||||||
| Not married | 136 (36.5) | 195 (47.0) | |||||
| Married | 237 (63.5) | 165 (39.8) | |||||
| Missing | 0 | 55 (13.3) | |||||
| Maternal IQ | 373 | 99.4 (10.4) | 57–124 | 262 | 95.8 (10.2) | 72–126 | < 0.01* |
| Seafood during pregnancy (serv/day) | 373 | 0.5 (0.6) | 0–5.3 | 260 | 0.6 (0.7) | 0–6 | 0.6 |
| Smoking during pregnancy | 0.1 | ||||||
| No | 272 (72.9) | 210 (50.6) | |||||
| Yes | 101 (27.1) | 103 (24.8) | |||||
| Missing | 0 | 102 (24.6) | |||||
| Household Characteristics at Birth | |||||||
| Maternal education | < 0.01* | ||||||
| ≤ High School | 190 (50.9) | 231 (55.7) | |||||
| > High School | 183 (49.1) | 127 (30.6) | |||||
| Missing | 0 | 57 (13.7) | |||||
| Paternal Education | < 0.01* | ||||||
| ≤ High School | 246 (66.0) | 266 (64.1) | |||||
| > High School | 127 (34.0) | 81 (19.5) | |||||
| Missing | 0 | 68 (16.4) | |||||
| Annual Household Income | < 0.01* | ||||||
| < $20,000 | 115 (30.8) | 150 (36.1) | |||||
| ≥ $20,000 | 258 (69.2) | 201 (48.4) | |||||
| Missing | 0 | 64 (15.4) | |||||
| Examination Characteristics | |||||||
| Examiner | 0.4 | ||||||
| 1 | 277 (74.3) | 121 (29.2) | |||||
| 2 | 96 (25.7) | 34 (8.2) | |||||
| Missing | 0 | 260 (62.7) | |||||
Main analysis group: complete working memory outcome, covariate and exposure data for DDE, HCB, PCBs, Pb and Mn, n=373.
P-values represent results comparing characteristics between participants included in Set 1 and those excluded from Set 1 using t-tests and chi-square tests. Categorical covariate comparisons based on the distribution of non-missing values.
NBC participants with missing working memory measures: Verbal Working Memory n=260; Symbolic Working Memory n=261; Working Memory Index n=261.
NBC participants with missing exposure measures: DDE n=37; HCB n=37; ΣPCB4 n=37; Pb n= 40; Mn n=80.
NBC participants with missing covariate measures: age at exam n=260; HOME score n= 297; maternal IQ n=153; seafood during pregnancy n= 155.
p < 0.05.
Abbreviations: DDE: dichlorodiphenyldichloroethylene; HCB: hexachlorobenzene; ΣPCB4: Sum of 4 PCB congeners (118, 138, 153, 180); Pb: lead; Mn: manganese.