Table 1.
Participant Characteristics According to Randomization Group
| Characteristic | N | Iron-Fortified (N=216) | Low-Iron (N=189) |
|---|---|---|---|
| Infancy | |||
| Male sex, % | 405 | (99, 45.8%) | (89, 47.1%) |
| Gestational age, wk | 404 | 39.4 (1.1) | 39.4 (1.1) |
| Birth weight, g | 404 | 3504.1 (352.6) | 3504.2 (362.1) |
| Hemoglobin at 6mo, g/L | 405 | 115.5 (8.0) | 116.1 (7.0) |
| Hemoglobin at 12mo, g/L | 405 | 124.6 (8.6) | 123.1 (8.5) |
| Age at first bottle, m | 393 | 2.1 (1.7) | 2.2 (1.9) |
| Formula intake, ml/day | 405 | 528.0 (164.0) | 541.5 (155.4) |
| Maternal education a, y | 404 | 9.3 (2.8) | 9.3 (2.9) |
| Primary school or less, % | 280 | (153, 70.8%) | (127, 67.6%) |
| High school (9–12), % | 79 | (41, 19.0%) | (38, 20.2%) |
| Some higher education, % | 45 | (22, 10.2%) | (23, 12.2%) |
| Paternal education a, y | 403 | 9.7 (3.0) | 9.7 (3.0) |
| Primary school or less, % | 252 | (141, 65.3%) | (111, 59.4%) |
| High school (9–12), % | 113 | (55, 25.5%) | (58, 31.0%) |
| Some higher education, % | 38 | (20, 9.3%) | (18, 9.6%) |
| Father present | 400 | (179, 83.6%) | (154, 82.8%) |
| Maternal age at birth, y | 398 | 25.6 (5.5) | 26.8 (6.2) |
| Maternal parity | 404 | 2.1 (1.2) | 2.1 (1.1) |
| Maternal IQ b | 401 | 84.4 (9.5) | 84.6 (10.7) |
| Maternal depression c | 394 | 16.5 (11.4) | 16.4 (12.0) |
| Socioeconomic Status d | 402 | 27.7 (6.3) | 28.4 (6.6) |
| Life stress e | 389 | 4.9 (2.5) | 4.9 (2.7) |
| Home Observation for Measurement of the Environment f | 402 | 30.2 (4.8) | 30.4 (4.7) |
| Adolescence | |||
| Age at assessment, y | 405 | 16.2 (0.2) | 16.2 (0.3) |
| Education (10–11 grade) | 380 | (156, 78.3%) | (132, 77.1%) |
| Hematocrit, % | 384 | 40.9 (3.8) | 41.2 (3.7) |
| Hemoglobin, g/L | 384 | 141.8 (13.8) | 142.3 (12.7) |
| Mean cell volume, fl | 384 | 85.2 (4.0) | 85.3 (3.9) |
| Protoporphyrin, ug/dlGR | 384 | 63.5 (12.8) | 65.2 (14.3) |
| Ferritin, ug/L | 383 | 28.2 (16.2) | 25.8 (15.1) |
Values are (N, %) for categorical values and mean (sd) for continuous variable
a
Between 1965 – 2003, education in Chile was compulsory from ages 6 to 13. In 2003, school became mandatory to 18 years old.
b
Maternal IQ evaluated by using the WAIS (18)
c
Maternal Depression evaluated by using the CESD(28)
d
Social class index evaluated by using Graffar (17)
e
Life stress evaluated by using the social readjustment rating scale(20)
f
Home Observation for Measurement of the Environment(19)