Table 4. Difference (95% confidence interval) in mean AH4 score according to father's age at respondent's birth stratified by number of older siblings.
| N | Adjusted for age at IQ measurement | Adjusted for age and father's education1 | Adjusted for age and father's SES1 | Multiply adjusted2 | |
| Respondents with no older siblings (N = 283) | |||||
| <25 | 102 | −2.41 (−5.03, 0.22) | −2.07 (−4.66, 0.52) | −1.45 (−3.97, 1.08) | −1.49 (−4.01, 1.03) |
| 25–29 | 107 | 0.00 (ref) | 0.00 (ref) | 0.00 (ref) | 0.00 (ref) |
| 30–34 | 55 | 5.00 (1.84, 8.16) | 4.85 (1.74, 7.97) | 4.05 (1.02, 7.07) | 4.20 (1.17, 7.22) |
| 35+ | 19 | 5.16 (0.42, 9.90) | 5.00 (0.34, 9.66) | 6.25 (1.73, 10.77) | 6.08 (1.57, 10.60) |
| P3 | <0.001 | <0.001 | <0.001 | <0.001 | |
| Respondents with one older sibling (N = 233) | |||||
| <25 | 32 | −4.45 (−8.48, −0.43) | −3.50 (−7.35, 0.34) | −2.26 (−6.16, 1.63) | −2.23 (−6.06, 1.60) |
| 25–29 | 88 | 0.00 (ref) | 0.00 (ref) | 0.00 (ref) | 0.00 (ref) |
| 30–34 | 81 | 1.37 (−1.63, 4.37) | 0.78 (−2.06, 3.63) | 0.58 (−2.32, 3.47) | 0.40 (−2.43, 3.24) |
| 35+ | 32 | 0.55 (−3.47, 4.57) | 0.07 (−3.74, 3.88) | 0.03 (−3.82, 3.87) | −0.11 (−3.89, 3.65) |
| P3 | 0.04 | 0.18 | 0.56 | 0.60 | |
| Respondents with two or more older siblings (N = 256) | |||||
| <25 | 10 | −3.36 (−9.64, 2.93) | −3.57 (−9.72, 2.58) | −2.81 (−9.05, 3.44) | −3.13 (−9.31, 3.05) |
| 25–29 | 59 | 0.00 (ref) | 0.00 (ref) | 0.00 (ref) | 0.00 (ref) |
| 30–34 | 81 | 2.21 (−0.95, 5.36) | 1.26 (−1.87, 4.38) | 1.71 (−1.43, 4.86) | 1.11 (−2.02, 4.25) |
| 35+ | 106 | 0.45 (−2.53, 3.42) | −0.04 (−2.96, 2.89) | −0.11 (−3.08, 2.86) | −0.29 (−3.23, 2.65) |
| P3 | 0.21 | 0.40 | 0.34 | 0.48 | |
1
Adjustment for mother's education and SES had a similar or weaker impact on these associations; 2Adjusted for age, father's education, and father's SES; 3p for heterogeneity based on likelihood ratio test.