Table 1.
Frequency distributions of study variables, according to sample
| Observed sample (no restrictions) (n = 18 296) |
Multiply imputed sample (n = 12 201) |
Complete case sample (n = 4610) |
|
|---|---|---|---|
| Sex of child | |||
| Male | 51.5 (9415) | 50.5 | 49.1 (2263) |
| Female | 48.5 (8881) | 49.5 | 50.9 (2347) |
| Baseline confounders (9 months) | |||
| Maternal highest qualification | |||
| Degree | 15.7 (2860) | 19.3 | 25.0 (1153) |
| Diploma | 8.4 (1525) | 9.7 | 11.3 (519) |
| A/AS/S levels | 9.3 (1696) | 10.6 | 12.4 (572) |
| O levels/GCSEs A-C | 33.5 (6100) | 34.9 | 36.4 (1584) |
| O levels/GCSEs D-G | 10.8 (1961) | 10.1 | 8.2 (376) |
| Other/none | 22.4 (4087) | 15.4 | 8.8 (406) |
| Item missing | 67 | ||
| Number of children | |||
| 1 child | 42.1 (7695) | 42.7 | 42.2 (1943) |
| 2 children | 34.5 (6320) | 35.5 | 38.6 (1777) |
| 3 children | 20.7 (3795) | 19.9 | 18.2 (839) |
| 4+ children | 2.7 (486) | 1.9 | 1.1 (51) |
| Maternal age at cohort child's birth | |||
| 14–19 years | 8.7 (1589) | 7.5 | 5.1 (234) |
| 20–29 years | 46.9 (8579) | 44.2 | 40.2 (1855) |
| 30–39 years | 42.3 (7736) | 46.0 | 52.1 (2400) |
| 40 years and above | 2.1 (389) | 2.3 | 2.6 (121) |
| Item missing | 3 | ||
| Ethnicity | |||
| White | 83.9 (15 315) | 90.4 | 95.7 (4411) |
| Indian | 2.6 (476) | 1.9 | 0.9 (43) |
| Pakistani/Bangladeshi | 6.9 (1256) | 3.3 | 1.2 (53) |
| Black/Black British | 3.7 (667) | 2.5 | 1.2 (57) |
| Other/mixed | 2.9 (533) | 1.8 | 1.0 (46) |
| Item missing | 49 | ||
| Lone parent family | |||
| Two parents | 82.7 (15 128) | 85.4 | 90.1 (4153) |
| One parent | 17.3 (3160) | 14.6 | 9.9 (457) |
| Item missing | 8 | ||
| Time-varying confounders | |||
| Family circumstances at 3 years | |||
| Adverse circumstances | 32.4% (4761) | 29.1% | 19.4% (894) |
| Not Adverse | 67.6% (9935) | 70.9% | 80.6% (3716) |
| Not present at relevant sweep (3 years) | 3600 | ||
| Family circumstances at 5 years | |||
| Adverse circumstances | 33.4% (4828) | 28.7% | 19.1% (881) |
| Not Adverse | 66.7% (9650) | 71.3% | 80.9% (3729) |
| Not present at relevant sweep (5 years) | 3818 | ||
| Family circumstances at 7 years | |||
| Adverse circumstances | 29.5% (3891) | 26.0% | 17.7% (814) |
| Not Adverse | 70.5% (9301) | 74.0% | 82.3% (3796) |
| Not present at relevant sweep (7 years) | 5104 | ||
| Family circumstances at 11 years | |||
| Adverse circumstances | 22.6% (2858) | 19.1% | 11.5% (529) |
| Not Adverse | 77.4% (9784) | 80.9% | 88.5% (4081) |
| Not present at relevant sweep (11 years) | 5654 | ||
| Exposure variables | |||
| K6 at 3 years | |||
| No | 88.5 (11 580) | 89.2 | 91.8 (4230) |
| Yes | 11.5 (1503) | 10.8 | 8.2 (380) |
| Scale items missing | 1613 | ||
| Not present at relevant sweep (3 years) | 3600 | ||
| K6 at 5 years | |||
| No | 88.2 (12 032) | 89.2 | 91.8 (4232) |
| Yes | 11.8 (1617) | 10.8 | 8.2 (378) |
| Scale items missing | 829 | ||
| Not present at relevant sweep (5 years) | 3818 | ||
| K6 at 7 years | |||
| No | 88.4 (10 781) | 89.2 | 92.1 (4246) |
| Yes | 11.6 (1413) | 10.8 | 7.9 (364) |
| Scale items missing | 998 | ||
| Not present at relevant sweep (7 years) | 5104 | ||
| K6 at 11 years | |||
| No | 82.7 (9187) | 83.6 | 87.9 (4054) |
| Yes | 17.3 (1923) | 16.4 | 12.1 (556) |
| Scale items missing | 1532 | ||
| Not present at relevant sweep (11 years) | 5654 | ||
| Outcome variables | |||
| SDQ at 3 years | |||
| No | 82.5 (7926) | 82.2 | 87.2 (4018) |
| Yes | 17.5 (1676) | 17.8 | 12.8 (592) |
| Scale items missing | 5094 | ||
| Not present at relevant sweep (3 years) | 3600 | ||
| SDQ at 5 years | |||
| No | 90.4 (10 044) | 90.4 | 94.0 (4332) |
| Yes | 9.6 (1065) | 9.6 | 6.0 (278) |
| Scale items missing | 3369 | ||
| Not present at relevant sweep (5 years) | 3818 | ||
| SDQ at 7 years | |||
| No | 88.3 (9332) | 88.1 | 92.3 (4255) |
| Yes | 11.7 (1242) | 11.9 | 7.7 (355) |
| Scale items missing | 2618 | ||
| Not present at relevant sweep (7 years) | 5104 | ||
| SDQ at 11 years | |||
| No | 86.2 (9551) | 86.6 | 90.4 (4166) |
| Yes | 13.8 (1534) | 13.4 | 9.6 (444) |
| Scale items missing | 1557 | ||
| Not present at relevant sweep (11 years) | 5654 |