Table 1 Participants and measures
Sweden | Denmark | Finland | |
|---|---|---|---|
Initial data collection (years) | 1992 – 1994 | 1990–1992 | 1985 – 1986 |
Initiated during gestational week | 10 | 14 | 12 |
Geographic area | Uppsala | Aarhus | Northern Finland |
County | (Oulu Lapland Provinces) | ||
Inclusion criteria | nulliparity + Scandinavian origin | all pregnant women | all pregnant women |
Sample size | |||
Mothers (% of eligible) | 476 (91%) | 8010 (98%) | 9362 (99%) |
live births | 411 | 8244 | 9432 |
Maternal age (Y, sd) | 27.0 (4) | 28.6(5) | 27.8 (6) |
Family structure at birth | |||
cohabitated with expectant father | 91% | 95% | 95% |
Follow-up data collection | 2001–2002 | 2001 | 1993–1994 |
Retained at follow-up | 290 (74%) | 5039 (61%) | 9297 (99%) |
Sample size: | |||
Participating eligible teachers1 | 208 (96%) | 4354 (85%) | 8525 (92%) |
Child age (years) | 7–8 | 10–12 | 7–8 |
Child gender (% boys) | 49% | 51% | 51% |
Maternal education (%) | |||
secondary | 85.7 | 90.6 | 90.5 |
college/university2 | 15.2 | 9.5 | 9.5 |
Family structure | |||
two biological parents | 78.1% | 78.2% | 87.8% |
disrupted family3 | 21.9% | 21.8% | 12.2% |
Inattention & hyperactivity symptoms assessment | SDQ4 | SDQ4 | CBQ5 |
Scholastic performance: | |||
writing, reading, mathematics | 7-pt scale | 5-pt scale | impaired/unimpaired |