Multivariable associations of parental characteristics with IQ at ages 7 among n = 10 690 participants with complete data on all variables included in any model (for maternal physical condition 25% of the values were multiply imputed and for birthweight z score 10% of the values were multiply imputed)
| Mean difference (95% CI) by exposure category with adjustment for: | ||||||||
|---|---|---|---|---|---|---|---|---|
| Model 1: Sex | Model 2: + other parental characteristics* | Model 3: + complications of pregnancy† | Model 4 + intrauterine growth‡ | Model 5: + postnatal linear growth§ | Model 6: + postnatal weight¶ | Model 7 + number of siblings** | ||
| All models include covariates that were in the earlier model. *Adjusted for sex and mutually adjusted for all other parental characteristics listed in the first column of the table. †Adjusted for all covariates include in model 2 plus pregnancy induced hypertension, antepartum haemorrhage, artificial rupture of membranes, and method of delivery. ‡Adjusted for all covariates included in model 3 plus gestational age and sex standardised birth weight z scores. §Adjusted for all covariates included in model 4 plus age and sex standardised childhood height z scores. ¶Adjusted for all covariates included in model 5 plus age and sex standardised childhood weight z scores. **Adjusted for all covariates included in model 6 plus number of siblings that the child indicated they had at the time of the 1962 survey. | ||||||||
| Social class at birth | I and II | Ref | ref | ref | ref | ref | ref | ref |
| III NM | −6.29 (−7.58, −5.00) | −5.70 (−6.98, −4.42) | −5.70 (−6.97, −4.42) | −5.66 (−6.94, −4.39) | −5.45 (−6.73, −4.17) | −5.48 (−6.73, −4.18) | −5.23 (−6.49, −3.97) | |
| III M | −11.72 (−12.77, −10.65) | −10.49 (−11.55, 9.42) | −10.38 (−11.45, −9.32) | −10.31 (−11.38, −9.25) | −9.91 (−10.97, −8.84) | −9.88 (−10.94, −8.82) | −9.19 (−10.25, −8.14) | |
| IV | −16.27 (−17.51, −15.03) | −14.42 (−15.67, −13.16) | −14.14 (−15.40, −12.88) | −14.07 (−15.33, −12.82) | −13.54 (−14.80, −12.28) | −13.49 (−14.74, −12.23) | −12.22 (−13.47, −10.98) | |
| V (lowest) | −18.62 (−19.83, −17.41) | −16.71 (−17.95, −15.48) | −16.47 (−17.71, −15.24) | −16.37 (−17.61, −15.14) | −15.58 (−16.81, −14.34) | −15.50 (−16.74, −14.26) | −13.93 (−15.16, −12.70) | |
| p trend | <0.001 | <0.001 | <0.001 | <0.001 | <0.001 | <0.001 | <0.001 | |
| Gravidity | 1 | Ref | ref | ref | ref | ref | ref | ref |
| 2 | −1.03 (−1.81, −0.25) | −2.53 (−3.31, −1.75) | −2.41 (−3.23, −1.60) | −2.76 (−3.58, −1.94) | −2.44 (−3.26, −1.63) | −2.00 (−2.82, −1.19) | −1.08 (−1.87, −0.28) | |
| 3 | −3.22 (−4.13, −2.33) | −5.69 (−6.62, −4.77) | −5.49 (−6.46, −4.51) | −5.90 (−6.87, −4.92) | −4.41 (−5.38, −3.44) | −3.87 (−4.85, −2.89) | −2.19 (−3.14, −1.24) | |
| 4 | −5.62 (−6.74, −4.50) | −8.70 (−9.87, −7.53) | −8.45 (−9.67, −7.24) | −8.92 (−10.14, −7.71) | −6.04 (−7.26, −4.82) | −5.96 (−7.18, −4.74) | −2.19 (−3.38, −1.00) | |
| ⩾5 | −9.48 (−10.62, −8.34) | −13.63 (−14.89, −12.39) | −13.40 (−14.70, −12.10) | −13.94 (−15.24, −12.63) | −10.84 (−12.16, −9.53) | −8.73 (−10.04, −7.42) | −3.37 (−4.66, −2.08) | |
| p trend | <0.001 | <0.001 | <0.001 | <0.001 | <0.001 | <0.001 | <0.001 | |
| Born outside of marriage | No | Ref | ref | ref | ref | ref | ref | ref |
| Yes | −9.51 (−13.80, −5.22) | −7.17 (−11.46, −2.88) | −6.82 (−11.11, −2.53) | −7.01 (−11.30, −2.72) | −7.00 (−11.30, −2.73) | −6.58 (−10.87, −2.29) | −6.20 (−10.50, −1.91) | |
| p trend | <0.001 | <0.001 | <0.001 | <0.001 | <0.001 | <0.001 | 0.004 | |
| Maternal age at birth (years) | 15–19 | Ref | ref | ref | ref | ref | ref | ref |
| 20–24 | 4.00 (2.24, 5.76) | 4.52 (2.76, 6.28) | 4.56 (2.80, 6.32) | 4.56 (2.80, 6.33) | 4.43 (2.67, 6.19) | 4.40 (2.64, 6.16) | 3.52 (1.76, 5.28) | |
| 25–29 | 6.90 (5.14, 8.66) | 7.88 (6.12, 9.64) | 7.87 (6.11, 9.63) | 7.83 (6.08, 9.59) | 7.58 (5.82, 9.34) | 7.57 (5.81, 9.33) | 5.94 (4.18, 7.70) | |
| 30–34 | 7.67 (5.86, 9.48) | 9.34 (7.53, 11.15) | 9.41 (7.60, 11.22) | 9.30 (7.49, 11.11) | 9.01 (7.20, 10.81) | 8.97 (7.16, 10.78) | 7.00 (5.19, 8.81) | |
| 35–39 | 8.20 (6.41, 9.98) | 10.74 (8.96, 12.52) | 10.77 (8.99, 12.55) | 10.60 (8.82, 12.38) | 10.11 (8.33, 11.90) | 10.09 (8.31, 11.87) | 7.74 (5.96, 985) | |
| ⩾40 | 7.19 (4.20, 10.17) | 11.74 (8.73, 14.74) | 11.73 (8.73, 14.75) | 11.59 (8.58, 14.59) | 11.00 (7.99, 14.00) | 10.99 (7.99, 13.99) | 8.68 (5.69, 11.67) | |
| p trend | <0.001 | <0.001 | <0.001 | <0.001 | <0.001 | <0.001 | <0.001 | |
| Maternal height (inches) | ⩽60 | Ref | ref | ref | ref | ref | ref | ref |
| 61 | 1.20 (0.28, 2.12) | −0.01 (−0.93, 0.91) | 0.04 (−0.88, 0.96) | −0.13 (−1.05, 0.79) | −0.38 (−1.30, 0.54) | −0.40 (−1.32, 0.52) | −0.40 (−1.32, 0.52) | |
| 62 | 3.01 (2.10, 3.92) | 1.52 (0.61, 2.43) | 1.56 (0.65, 2.47) | 1.17 (0.26, 2.08) | 0.93 (0.01, 1.82) | 0.92 (0.01, 1.81) | 0.96 (0.05, 1.86) | |
| 63 | 3.21 (2.23, 4.19) | 1.51 (0.53, 2.49) | 1.54 (0.56, 2.51) | 1.12 (0.14, 2.09) | 0.63 (−0.35, 1.61) | 0.55 (−0.43, 1.53) | 0.58 (−0.40, 1.56) | |
| 64 | 4.89 (3.85, 5.93) | 2.27 (1.23, 3.31) | 2.29 (1.25, 3.33) | 1.69 (0.65, 2.73) | 1.05 (0.01, 2.09) | 1.04 (−0.04, 2.01) | 1.02 (−0.02, 2.06) | |
| ⩾65 | 5.03 (4.00, 6.06) | 1.69 (0.66, 2.73) | 1.82 (0.79, 2.85) | 1.14 (0.11, 2.17) | 0.37 (−0.66, 1.40) | 0.24 (−0.79, 1.27) | 0.23 (−0.80, 1.27) | |
| p trend | <0.001 | <0.001 | <0.001 | 0.001 | 0.04 | 0.09 | 0.12 | |
| Maternal physical condtion | Very good or good | Ref | ref | ref | ref | ref | ref | ref |
| Mediocre | −3.43 (−4.20, −2.66) | −2.00 (−2.37, −0.88) | −1.70 (−2.75, −1.26) | −1.97 (−2.71, −1.24) | −1.44 (−2.29, −0.78) | −1.47 (−2.29, −0.64) | −1.31 (−2.24, −0.78) | |
| Very bad or bad | −6.86 (−8.38, −5.33) | −4.68 (−6.00, −3.36) | −4.63 (−5.98, −3.27) | −4.48 (−5.84, −3.12) | −4.42 (−5.76, −3.08) | −4.13 (−5.51, −2.75) | −3.67 (−5.21, −2.13) | |
| p trend | <0.001 | <0.001 | <0.001 | <0.001 | <0.001 | <0.001 | <0.001 | |