Table 1.
Description of potential demographic, socioeconomic, and behavioral predictors of low IQ and unadjusted associations*
| Characteristic | Rate n (%) | Low IQ n (%) | Unadjusted OR (95% CI) |
|---|---|---|---|
| All | 3523 (100) | 594 (16.9) | |
| Mother’s and father’s skin color (n = 3518) | p = 0.0000 | ||
| White mother and father or either one | 2736 (77.8) | 373 (13.6) | 1 |
| Non-white mother and father | 782 (22.2) | 219 (28.0) | 2.5 (2.0–3.0) |
| Teenage parents (n = 3522) | p = 0.0007 | ||
| Neither | 2776 (78.8) | 436 (15.7) | 1 |
| Both or either one | 746 (21.2) | 157 (21.1) | 1.4 (1.2–1.8) |
| Mother with a partner (n = 3522) | p = 0.0069 | ||
| No | 556 (15.8) | 116 (20.9) | 1.4 (1.1–1.7) |
| Yes | 2966 (84.2) | 477 (16.1) | 1 |
| Father employed at the child’s birth (n = 3445) | p = 0.0000 | ||
| No | 590 (17.1) | 155 (26.3) | 2.1 (1.7–2.6) |
| Yes | 2855 (82.9) | 412 (14.4) | 1 |
| Mother employed between pregnancy and the child’s first 12 months of life (n = 3456) | p = 0.0000 | ||
| No | 1645 (47.6) | 359 (21.8) | 2.0 (1.7–2.4) |
| Employed either during pregnancy or the child’s first 12 months of life | 1811 (52.4) | 220 (12.2) | 1 |
| Household income at the child’s birth (n = 3522) | p = 0.0000 | ||
| One or less than one monthly minimum wage | 823 (23.4) | 248 (30.1) | 7.6 (5.3–11.1) |
| Up to 2 monthly minimum wages | 1041 (29.6) | 213 (20.5) | 4.5 (3.1–6.6) |
| Up to 4 monthly minimum wages | 1004 (28.5) | 97 (9.7) | 1.9 (1.3–2.8) |
| More than 4 monthly minimum wages | 654 (18.6) | 35 (5.4) | 1 |
| Maternal education (years of schooling) (n = 3490) | p = 0.0000 | ||
| 0–4 | 527 (15.1) | 197 (37.4) | 9.4 (7.1–12.4) |
| 5–8 | 1458 (41.8) | 306 (21.0) | 4.2 (3.3–5.3) |
| 9 or more | 1505 (43.1) | 90 (6.0) | 1 |
| Number of siblings at the child’s birth (n = 3522) | p = 0.0000 | ||
| Two or less | 3149 (89.4) | 454 (14.4) | 1 |
| Three or more | 373 (10.6) | 139 (37.3) | 3.5 (2.8–4.4) |
| Number of persons per room at age 12 months (n = 3423) | p = 0.0000 | ||
| <3 | 1687 (49.3) | 190 (11.3) | 1 |
| ≥3 | 1736 (50.7) | 384 (22.1) | 2.2 (1.9–2.7) |
| Maternal level of physical activity during and after pregnancy (n = 3522) | p = 0.0000 | ||
| Physically inactive | 2844 (80.8) | 535 (18.8) | 2.5 (1.9–3.3) |
| Active either during or after pregnancy | 678 (19.2) | 58 (8.6) | 1 |
| Maternal and paternal smoking during pregnancy (n = 3522) | p = 0.0000 | ||
| None | 1982 (56.3) | 242 (12.2) | 1 |
| At least one parent smoked | 1540 (43.7) | 351 (22.8) | 2.1 (1.7–2.8) |
| Maternal smoking during the child’s first year of life (n = 3404) | p = 0.0000 | ||
| No | 2336 (68.6) | 330 (14.1) | 1 |
| Smoked | 1068 (31.4) | 247 (23.1) | 1.8 (1.5–2.2) |
| Number of father-child activities at age 12 months (n = 3424) | p = 0.0008 | ||
| 0–2 | 568 (16.6) | 117 (20.6) | 1.8 (1.3–2.5) |
| 3–6 | 2288 (66.8) | 387 (16.9) | 1.4 (1.1–1.9) |
| 7 activities** | 568 (16.6) | 70 (12.3) | 1 |
| Childcare during the first year of life (n = 3523) | p = 0.0008 | ||
| No | 3353 (95.2) | 580 (17.3) | 2.3 (1.3–4.1) |
| Yes | 170 (4.8) | 14 (8.2) | 1 |
*Logistic regression analysis in children age 6. The 2004 Pelotas Birth Cohort Study.
**Score estimated from the mother’s reports of the father spending time with the child feeding, diapering, bathing soothing during bedtime, playing, tending or strolling.
CI = confidence intervals; OR = odds ratios; IQ = intelligence quotient.