Table 1.
Characteristics of the study populations
| Pregnancy sample | Postnatal sample (5-year data example) | ||||||
|---|---|---|---|---|---|---|---|
| <45 dB | 45–55 dB | > = 55 dB | <45 dB | 45–55 dB | > = 55 dB | ||
| N (%) | 202 (10.4) | 620 (32.1) | 1112 (57.5) | N (%) | 158 (11.4) | 617 (44.6) | 587 (44.0) |
| Mean fraction of inattention score (SD) | .17 (.15) | .19 (.14) | .19 (.15) | Mean fraction of inattention score (SD) | .19 (.16) | .18 (.14) | .20 (.16) |
| % Boys | 47.5 | 49.4 | 49.9 | % Boys | 52.5 | 50.4 | 49.8 |
| Age, months (SD) | 97.3 (1.2) | 97.3 (1.3) | 97.5 (1.4) | Age, months (SD) | 97.3 (1.2) | 97.4 (1.4) | 97.5 (1.5) |
| Income, birth (SD)a | 825,843 | 824,736 | 757,927 | Average 5-y income (SD)a | 1,052,194 | 1,047,947 | 920,016 |
| (585473) | (685930) | (495249) | (585321) | (519580) | (542098) | ||
| Mother’s education | Mother’s education | ||||||
| > 4 years univ./college | 35.6 | 36.3 | 37.6 | > 4 years univ./college | 40.5 | 42.0 | 41.5 |
| ≤ 4 years univ./college | 52.5 | 48.2 | 50.4 | ≤ 4 years univ./college | 47.5 | 45.7 | 44.3 |
| High school | 11.9 | 15.5 | 12.1 | High school | 12.0 | 12.3 | 14.1 |
| Ethnicity: % westernb | 96.5 | 93.1 | 93.5 | Ethnicity: % westernb | 92.4 | 94.3 | 88.0 |
| Prematurec, % | 4.5 | 4.2 | 4.3 | Prematurec, % | 8.2 | 4.1 | 3.9 |
| Low birth weightd, % | 1.5 | 2.9 | 3.0 | Low birth weightd, % | 3.2 | 2.9 | 4.3 |
| Urbanity | Urbanity, birth | ||||||
| City center | 9.9 | 8.6 | 34.8 | City center | |||
| Between | 19.3 | 27.4 | 30.0 | Between | |||
| Outskirts | 70.8 | 64.0 | 35.3 | Outskirts | |||
| Urbanity,5-y average (SD) | Urbanity, 5-y average (SD) | 2.77 (.48) | 2.77 (.43) | 2.40 (.72) | |||
| Maternal alcohol, Pregnancye, % yes | 7.9 | 7.4 | 7.0 | Maternal alcohol, Pregnancye, % yes | 7.0 | 10.2 | 9.5 |
| Maternal smoking, Pregnancyf, % yes | 3.5 | 3.1 | 4.5 | Maternal smoking, Pregnancyf, % yes | 3.8 | 3.4 | 5.1 |
| Sleep duration at age 8 | Sleep duration at age 8 | ||||||
| > 10 h | > 10 h | 20.9 | 14.3 | 18.2 | |||
| 10 h | 10 h | 62.0 | 66.6 | 63.4 | |||
| < 10 h | < 10 h | 17.1 | 19.1 | 18.4 | |||
aAdjusted according to consumer price index. Average of incomes at ages 3, 5, 7 and 8 years, or at birth. Used as a categorical variable in the analyses: <500,000, > = 500,000–800,000, > = 800,000–1,100,000, > = 1,100,000
bDichotomized according to Statistics Norway [53]
cGestational age of less than 259 days
dBirth weight of less than 2500 g
eConsumed alcohol once a week or more during either of the trimesters
fSmoked sometimes or daily during the last trimester