Table 1 -.
Birth and parental characteristics*
| ‘76-’82 cohort | ‘96-’00 cohort | ||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Unweighted statistics | Weighted statistics | Unweighted statistics | Weighted statistics | ||||||||||||
| Characteristic | Unexposed (n=4,876) | Singly exposed (n=375) | SD | Unexposed | Singly exposed | SD | Unexposed (n=463) | Singly exposed (n=457) | SD | Unexposed | Singly exposed | SD | |||
| Mother’s age (yeats) | 26.5 (4.7) | 26.9 (4.7) | 0.08 | 26.5 (4.7) | 26.5 (4.5) | <.01 | 29.3 (5.5) | 29.2 (5.7) | <.01 | 29.3 (5.5) | 29.3 (5.6) | <.01 | |||
| Father’s age (yeats) | 28.5 (5.4) | 29.1 (5.3) | 0.10 | 28.6 (5.4) | 28.5 (5.3) | 0.02 | 31.5 (6.5) | 31.3 (6.1) | 0.03 | 31.4 (6.4) | 31.4 (6.0) | <.01 | |||
| Mother’s education (yeats) | |||||||||||||||
| <12 | 343 (7%) | 22 (6%) | 0.05 | (7%) | (6%) | 0.04 | 38 (8%) | 45 (10%) | 0.06 | (9%) | (9%) | 0.01 | |||
| 12 | 1584 (32%) | 120 (32%) | 0.01 | (32%) | (33%) | <.01 | 80 (17%) | 80 (18%) | <.01 | (17%) | (17%) | 0.01 | |||
| 13–15 | 1684 (35%) | 129 (34%) | <.01 | (35%) | (34%) | <.01 | 125 (27%) | 120 (26%) | 0.02 | (27%) | (27%) | 0.01 | |||
| ≥16 | 1265 (26%) | 104 (28%) | 0.04 | (26%) | (27%) | 0.02 | 220 (48%) | 212 (46%) | 0.02 | (47%) | (47%) | <.01 | |||
| Father’s education (years) | |||||||||||||||
| <12 | 337 (7%) | 20 (5%) | 0.07 | (7%) | (6%) | 0.02 | 31 (7%) | 33 (7%) | 0.02 | (7%) | (7%) | <.01 | |||
| 12 | 1394 (29%) | 102 (27%) | 0.03 | (28%) | (27%) | 0.02 | 104 (22%) | 100 (22%) | 0.01 | (22%) | (22%) | <.01 | |||
| 13–15 | 1262 (26%) | 91 (24%) | 0.04 | (26%) | (28%) | 0.04 | 110 (24%) | 120 (26%) | 0.06 | (25%) | (25%) | 0.01 | |||
| ≥16 | 1883 (39%) | 162 (43%) | 0.09 | (39%) | (39%) | <.01 | 218 (47%) | 204 (45%) | 0.05 | (46%) | (46%) | 0.02 | |||
| Parents married at time of birth | 4522 (93%) | 353 (94%) | 0.06 | (93%) | (93%) | <.01 | 383 (83%) | 379 (83%) | <.01 | (83%) | (83%) | 0.02 | |||
| Male sex | 2469 (51%) | 253 (67%) | 0.35 | (52%) | (51%) | 0.01 | 272 (59%) | 275 (60%) | 0.03 | (59%) | (59%) | <.01 | |||
| Estimated gestational age (weeks) | 40.0 (2.0) | 39.9 (2.4) | 0.06 | 40.0 (2.0) | 40.1 (2.1) | 0.05 | 38.5 (2.6) | 38.6 (2.5) | 0.06 | 38.6 (2.5) | 38.6 (2.5) | <.01 | |||
| Birth weight (g) | 3474 (532) | 3418 (629) | 0.10 | 3471 (536) | 3496 (576) | 0.05 | 3336 (737) | 3356 (647) | 0.03 | 3356 (726) | 3353 (648) | <.01 | |||
| Apgar (1 min) | 8 (7, 9) | 8 (7, 9) | 0.08 | 8 (7, 9) | 8 (7, 9) | <.01 | |||||||||
| Apgar (5 min) | 9 (9, 10) | 9 (9, 10) | 0.15 | 9 (9, 10) | 9 (9, 10) | <.01 | |||||||||
| HOUSES (quartile) | |||||||||||||||
| 1st | 115 (25%) | 109 (24%) | 0.02 | (26%) | (25%) | 0.03 | |||||||||
| 2nd | 123 (27%) | 98 (21%) | 0.12 | (24%) | (24%) | 0.01 | |||||||||
| 3rd | 117 (25%) | 111 (24%) | 0.02 | (24%) | (24%) | <.01 | |||||||||
| 4th | 108 (23%) | 139 (30%) | 0.16 | (26%) | (27%) | <.01 | |||||||||
Exposure status is according to number of exposures prior to age 3. Numbers are n (%) for categorical variables and mean (standard deviation, SD) for continuous variables except for APGAR scores which are median (Q1, Q3). Both weighted and unweighted samples are summarized in both time-frames. Unweighted characteristics differ across time-frames due to sample selection methods. The. HOUSES index (a measure of socioeconomic status) was not available for ‘76-’82 cohort. APGAR scores were missing for 70% of subjects in the ‘76-’82 cohort and therefore were not included in the propensity models or summary statistics. To account for missing data, multiple-imputation was used. This table summarizes a single imputation and therefore has no missing data. In the ‘76-’82 cohort, data were missing for father’s age (n=271, 5.2%), mother’s education (n=447, 8.5%), father’s education (n=718, 13.7%), gestational age (n=327, 6.2%), and birth weight (n=10, 0.2%). In the ‘96-’00 cohort, data were missing for father’s age (n=41, 4.5%), mother’s education (n=16, 1.7%), father’s education (n=78, 8.5%), and HOUSES (n=88, 9.6%).