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Table 4 Confounding scenarios for indirect ICS effect on BW

From: On the use of the outcome variable “small for gestational age” when gestational age is a potential mediator: a maternal asthma perspective

Scenario
(model, interpretation of effect)
mean se null ICS effect? association confounded?
Confounding 1 (M1, total) −513.25 0.2041 no yes
Confounding 1 (M1,V, total) −366.72 0.2189 no no
Confounding 1 (M2, direct) −0.1645 0.1814 yes no
Confounding 1 (M2,V, direct) −0.1614 0.1823 yes no
Confounding 1 (M3, total) 1.7763 0.0017 no yes
Confounding 1 (M3,V, total) 1.3296 0.0018 no no
Confounding 1 (M4, direct) −0.0011 0.0015 yes no
Confounding 1 (M4,V, direct) −0.0001 0.0016 yes no
Confounding 2 (M1, total) −366.44 0.2292 no no
Confounding 2 (M1,V, total) −366.56 0.1973 no no
Confounding 2 (M2, direct) 24.232 0.1690 no yes
Confounding 2 (M2,V, direct) −0.1271 0.1694 yes no
Confounding 2 (M3, total) 1.2508 0.0014 no no
Confounding 2 (M3,V, total) 1.3351 0.0014 no no
Confounding 2 (M4, direct) 0.0008 0.0013 yes no
Confounding 2 (M4,V, direct) 0.0010 0.0013 yes no
Confounding 3 (M1, total) −406.67 0.1950 no yes
Confounding 3 (M1,V, total) −366.72 0.2189 no no
Confounding 3 (M2, direct) −40.136 0.1714 no yes
Confounding 3 (M2,V, direct) −0.1614 0.1823 yes no
Confounding 3 (M3, total) 1.4315 0.0021 no yes
Confounding 3 (M3,V, total) 1.2931 0.0023 no no
Confounding 3 (M4, direct) 0.2212 0.0013 no yes
Confounding 3 (M4,V, direct) 0.0006 0.0014 yes no
Confounding 4 (M1, total) −553.24 0.2109 no yes
Confounding 4 (M1,V, total) −366.72 0.2189 no no
Confounding 4 (M2, direct) −10.382 0.1854 no yes
Confounding 4 (M2,V, direct) −0.1614 0.1823 yes no
Confounding 4 (M3, total) 1.8558 0.0016 no yes
Confounding 4 (M3,V, total) 1.3321 0.0016 no no
Confounding 4 (M4, direct) 0.2212 0.0013 no yes
Confounding 4 (M4,V, direct) 0.0006 0.0014 yes no
  1. Legend. Mean of the estimated exposure (ICS) effect (mean difference or log odds ratio) on the outcome (BW, LBW or SGA) based on 1000 samples of size 20,000, with Monte Carlo standard error (se)
  2. Confounding Scenario 1: confounder between ICS and GA; Confounding Scenario 2: confounder between GA and BW; Confounding Scenario 3: confounder between ICS and BW; Confounding Scenario 4: confounder between ICS, GA and BW
  3. M1: BW ~ ICS; M2: BW ~ ICS + GA; M3: LBW ~ ICS; M4: SGA ~ ICS;
  4. null ICS effect = yes if 0 mean ± 1.96se
  5. Models subscripted by V additionally include the V variable in the regression model
  6. Abbreviations: BW birth weight, GA gestational age, ICS inhaled corticosteroids, LBW low birth weight, SGA small for gestational age