Table 1.
Characteristics of 573 Mother-Child Pairs (Children Born in 1993–1998) in the New Bedford Cohort (Massachusetts) and Their Univariate Associations With Square-Root-Transformed Scores on the DSM-IV ADHD Total Subscale
| Characteristic | No. of Pairs | % | DSM-IV ADHD Total Subscale Score | Change in DSM-IV ADHD Total Subscale Scorea | ||
|---|---|---|---|---|---|---|
| Median | Mean (SD) | β | 95% CI | |||
| Child's age at examination, years | 8.2 | 8.3 (0.7) | 0.17 | −0.05, 0.40 | ||
| Child's sex | ||||||
| Male | 293 | 51.1 | 1.04 | 0.75, 1.32 | ||
| Female | 280 | 48.9 | 0 | Referent | ||
| Maternal age at child's birth, years | 26.6 | 26.7 (5.3) | −0.08 | −0.10, −0.05 | ||
| Marital status at child's birth | ||||||
| Never married/divorced/widowed | 238 | 41.5 | 0.83 | 0.53, 1.12 | ||
| Married | 335 | 58.5 | 0 | Referent | ||
| Marital status at child's school age (age 8 years) | ||||||
| Never married/divorced/widowed | 239 | 41.7 | 0.83 | 0.53, 1.13 | ||
| Married | 334 | 58.3 | 0 | Referent | ||
| Annual household income at child's birth (3 values missing) | ||||||
| <$20,000 | 194 | 33.9 | 0.97 | 0.61, 1.32 | ||
| $20,000–$39,999 | 188 | 32.8 | 0.56 | 0.20, 0.92 | ||
| ≥$40,000 | 188 | 32.8 | 0 | Referent | ||
| Annual household income at child's school age (8 values missing) | ||||||
| <$20,000 | 117 | 20.4 | 0.82 | 0.44, 1.20 | ||
| $20,000–$39,999 | 157 | 27.4 | 0.60 | 0.25, 0.94 | ||
| ≥$40,000 | 291 | 50.8 | 0 | Referent | ||
| Mother's education at child's birth (2 values missing) | ||||||
| Less than 12th grade | 95 | 16.6 | 0.90 | 0.48, 1.32 | ||
| High school graduation | 227 | 39.6 | 0.59 | 0.27, 0.91 | ||
| Any college | 249 | 43.5 | 0 | Referent | ||
| Father's education at child's birth (12 values missing) | ||||||
| Less than 12th grade | 142 | 24.8 | 1.22 | 0.84, 1.61 | ||
| High school graduation | 247 | 43.1 | 0.44 | 0.10, 0.79 | ||
| Any college | 172 | 30.0 | 0 | Referent | ||
| HOME scoreb (12 values missing) | 46.0 | 45.6 (5.3) | −0.11 | −0.14, −0.08 | ||
| Smoking status during pregnancy (41 values missing) | ||||||
| Yes | 158 | 27.6 | 0.83 | 0.51, 1.15 | ||
| No | 374 | 65.3 | 0 | Referent | ||
| Average smoking level during pregnancy (41 values missing), cigarettes/day | 0.0 | 2.5 (5.5) | 0.06 | 0.04, 0.09 | ||
| Exposure measuresc | ||||||
| ∑PCB4, ng/g | 0.2 | 0.3 (0.3) | ||||
| ρ,ρ′-DDE, ng/g | 0.3 | 0.5 (1.0) | ||||
| 12- to 36-month peak blood lead level (24 values missing), μg/dL | 6.0 | 6.7 (3.9) | ||||
| Peripartum maternal hair mercury level (176 values missing), μg/g | 0.4 | 0.6 (0.5) | ||||
| Townc | ||||||
| Acushnet | 29 | 5.1 | ||||
| Dartmouth | 62 | 10.8 | ||||
| Fairhaven | 60 | 10.5 | ||||
| New Bedford | 422 | 73.6 | ||||
Abbreviations: ADHD, attention-deficit/hyperactivity disorder; CI, confidence interval; ρ,ρ′-DDE, ρ,ρ′-dichlorodiphenyl dichloroethylene; DSM-IV, Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition; HOME, Home Observation for Measurement of the Environment; PCB, polychlorinated biphenyl; ∑PCB4, sum of 4 prevalent PCB congeners (congeners 118, 138, 153, and 180); SD, standard deviation.
a Association between the covariate and square-root-transformed DSM-IV ADHD Total subscale score in a model with spatial smoothing and the single covariate.
b The HOME Inventory (14) is a standardized instrument that uses a combination of questionnaire items and observation to assess the support available to the child from the physical attributes of his/her home surroundings, as well as the cognitive stimulation and emotional support a child receives from exchanges with family and interactions with objects such as books and toys. Scores can range from 0 to 59, where a higher score indicates a better home environment.
c Exposure variables and town were not included in the final spatial model.