TABLE 4.
Causal mediation analysis of co-morbidities at birth as mediator of the association between gestational age and cognitive outcome, controlling for maternal age and social disadvantage
| WASI-II IQ | NTCB verbal factor | NTCB fluid factor | |
|---|---|---|---|
| Total effect of gestational age1 | −3.1 (−4.5, −1.6) |
−1.3 (−2.2, −0.3) |
−1.7 (−2.6, −0.7) |
| Controlled direct effect of gestational age | −2.0 (−3.5, −0.5) |
−0.7 (−1.7, 0.3) |
−1.1 (−2.0, −0.2) |
| Natural direct effect of gestational age | −1.9 (−3.4, −0.4) |
−0.8 (−1.8, 0.2) |
−1.1 (−2.0, −0.2) |
| Natural indirect effect through morbidities | −1.1 (−1.7, −0.7) |
−0.5 (−0.8, −0.2) |
−0.6 (−0.9, −0.3) |
| Percentage mediated by morbidities | 37.2% (20.1%, 76.2%) |
36.7% (12.1%, 163.5%) |
33.9% (16.3%, 80.4%) |
| Percentage due to interaction | 2.1% (−3.0%, 10.5%) |
−2.3% (−27.3%, 5.9%) |
−1.0% (−9.4%, 5.5%) |
| Percentage eliminated | 35.0% (17.6%, 74.5%) |
39.1% (13.6%, 175.2%) |
34.9% (17.1%, 79.7%) |
1
Effects correspond to expected difference in the outcome for each additional week lower in gestational age