Table 1.
Descriptive Statistics
| N | Min | Max | M or % | SD | |
|---|---|---|---|---|---|
| Age at assessment (y) | |||||
| 5 y | 600 | 5.5 | 6.0 | 5.5 | 0.04 |
| 10 y | 822 | 9.9 | 10.5 | 10.0 | 0.1 |
| Adolescence | 933 | 11.8 | 17.8 | 14.4 | 1.5 |
| Sex (% female) | 933 | — | — | 48.3% | — |
| Maternal age at child’s birth (y) | 925 | 14.6 | 46.1 | 26.4 | 6.1 |
| Mother’s education (y) | 933 | 1 | 17 | 9.5 | 2.7 |
| Graffar (SES)a | 930 | 11 | 47 | 27.2 | 6.4 |
| HOME score | 929 | 12 | 42 | 30.5 | 4.7 |
| Maternal stress (number) | 912 | 0 | 14 | 4.7 | 2.6 |
| Formula/milk intake (average ml/day) | 864 | 0 | 1,157.3 | 416.3 | 207.6 |
| Iron status at 12–18 m | |||||
| Iron sufficient | 512 | — | — | 54.9% | — |
| ID w/o anemia | 294 | — | — | 31.5% | — |
| ID anemia | 127 | — | — | 13.6% | — |
| Supplementation group | |||||
| High iron | 353 | — | — | 40.8% | — |
| Low iron | 196 | — | — | 22.6% | — |
| No added iron | 317 | — | — | 36.6% | — |
| Received medicinal iron in infancy | 256 | — | — | 27.4% | — |
| 9 m maternal emotional/verbal responsivity | 569 | 2 | 11 | 8.4 | 1.9 |
| 9 m maternal involvement with child | 569 | 0 | 6 | 4.3 | 1.4 |
| 5 y maternal responsivity | 594 | 0 | 2 | 1.9 | 0.4 |
| 5 y maternal warmth/affection | 594 | 0 | 3 | 2.3 | 0.9 |
| 5 y maternal social stimulation | 594 | 0 | 8 | 5.5 | 1.7 |
| 5 y anxious | 590 | 6 | 20 | 13.0 | 3.0 |
| 5 y depressive | 590 | 6 | 21 | 9.6 | 2.7 |
| 5 y social isolation | 590 | 7 | 25 | 13.6 | 3.5 |
| 5 y social rejection | 590 | 7 | 25 | 12.1 | 3.0 |
| 5 y antisocial | 590 | 5 | 17 | 9.9 | 2.5 |
| 5 y hostile | 590 | 4 | 15 | 8.5 | 2.3 |
| 5 y oppositional | 590 | 6 | 23 | 13.2 | 3.4 |
| 10 y anxious/depressed | 819 | 50 | 96 | 63.0 | 8.9 |
| 10 y social problems | 819 | 50 | 93 | 61.8 | 9.1 |
| 10 y withdrawn | 819 | 50 | 97 | 62.7 | 9.3 |
| 10 y aggressive | 819 | 50 | 92 | 59.8 | 9.1 |
| 10 y delinquent | 819 | 50 | 84 | 57.0 | 7.4 |
| Adolescent anxious | 933 | 50 | 91 | 62.7 | 8.4 |
| Adolescent depressive | 933 | 50 | 91 | 61.9 | 8.5 |
| Adolescent social problems | 933 | 50 | 93 | 61.9 | 7.7 |
| Adolescent oppositional defiant | 933 | 50 | 80 | 58.1 | 7.1 |
| Adolescent conduct | 933 | 50 | 86 | 56.3 | 6.5 |
| Adolescent aggressive | 933 | 50 | 94 | 59.7 | 8.3 |
Note. Values are n (%) for categorical variables and mean (SD) for continuous variables. Iron status and supplementation group Ns indicate the number of participants (and percentage of total participants) in each group. Percentages were calculated for those with nonmissing data on each variable. y = years; m = months; SES = socioeconomic status; HOME = Home Observation for Measurement of the Environment; ID = iron deficiency.
a
Mean Graffar in this sample corresponds to middle SES class.