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Table 6 Estimates of Direct and Indirect Effects With and/or Without Mediator-outcome Interaction

From: Implementation and reporting of causal mediation analysis in 2015: a systematic review in epidemiological studies

References

Without exposure-mediator interaction (95 % confidence interval)

With exposure-mediator interaction (95 % confidence interval)

Discrepancy found with and without exposure-mediator interaction reason discussed

Banack et al. [26]

Not reported

Controlled direct effect with CVD

Risk ratio: 0.62 (0.49, 0.78)

Risk difference: −0.12 (−0.20, −0.04)

Controlled direct effect without CVD

Risk ratio: 1.30 (1.13, 1.49)

Risk difference: 0.03 (0.01, 0.05)

Total effect

Risk ratio: 1.24 (1.11, 1.39)

Risk difference: 0.03 (0.02, 0.05)

Not applicable

D’Amelio et al. [27]

Effects of treatment on glucose level at 12 months mediated by OC at 6 months:

Natural direct effect: −0.033 (−0.186, 0.121)

Natural indirect effect: −0.050 (−0.178, 0.078)

Total effect: −0.082 (−0.174, 0.009)

Not reported

Not applicable

Freeman et al. [28]

Anxiety (Boot SE), P value

Direct effect: 0.21 (0.16), 0.19

Indirect effect: 0.18 (0.11), 0.09

Total effect: 0.39 (0.16), 0.01

Depression (Boot SE), P value

Direct effect: 0.24 (0.14), 0.09

Indirect effect: 0.15 (0.11), 0.18

Total effect: 0.39 (0.16), 0.01

BCSS—negative self (Boot SE), P value

Direct effect: 0.33 (0.18), 0.06

Indirect effect: 0.06 (0.08), 0.48

Total effect: 0.39 (0.16), 0.01

BCSS—positive self (Boot SE), P value

Direct effect: 0.40 (0.17), 0.02

Indirect effect: −0.01 (0.05), 0.92

Total effect: 0.39 (0.16), 0.01

BCSS—negative other (Boot SE), P value

Direct effect: 0.22 (0.16), 0.17

Indirect effect: 0.18 (0.11), 0.13

Total effect: 0.39 (0.16), 0.01

Not applicable

Not applicable

Jackson et al. [29]

Stroke

Direct effect: 1.13 (1.05,1.22)

Indirect effect: 1.005 (1.001,1.011)

Total effect: 1.14 (1.06,1.22)

Stroke

Direct effect: 1.13 (1.06,1.22)

Indirect effect: 1.005 (1.001,1.011)

Total effect: 1.14 (1.06,1.22)

No

Not applicable

Kositsawat et al. [30]

Not reported

Not applicable

Not applicable

Louwies et al. [31]

Systolic blood pressure

Direct effect: 2.93 (CIs not reported)

Indirect effect: −0.42 (−1.35 to 0.17)

Total effect: not reported

Diastolic blood pressure

Direct effect: 3.15 (CIs not reported)

Indirect effect: −0.59 (−1.44 to 0.07)

Total effect: not reported

Not applicable

Not applicable

Lu et al. [32]

Overweight (for

metabolic mediators)

Blood pressure

Natural direct effect: 1.16 (1.09–1.24)

Natural indirect effect: 1.06 (1.03–1.08)

Total effect: 1.22 (1.14–1.30)

Obesity (for

metabolic mediators)

Blood pressure

Natural direct effect: 1.28 (1.15–1.43)

Natural indirect effect: 1.13 (1.07–1.19)

Total effect: 1.42 (1.25–1.60)

Overweight (for

metabolic mediators)

Blood pressure

Natural direct effect: 1.16 (1.09–1.24)

Natural indirect effect: 1.05 (1.02–1.08)

Total effect: 1.22 (1.14–1.30)

Obesity (for

metabolic mediators)

Blood pressure

Natural direct effect: 1.28 (1.15–1.42)

Natural indirect effect: 1.10 (1.03–1.17)

Total effect: 1.43 (1.25–1.62)

No

Not applicable

Mendola et al. [33]

Not reported

Peri- or intraventricular hemorrhage:

Controlled direct effect: 3.2 (1.4–7.7)

Total effect: 2.9 (2.4–3.4)

Not applicable

Messerlian et al. [34]

Uterine: <35 weeks

Controlled direct effect: 2.43 (0.85, 6.93)

Total effect: 2.27 (1.32, 3.89)

Not applicable

Not applicable

Raghavan et al. [35]

Metabolic syndrome score:

Direct effect: not reported

Indirect effect: 1.20 (1.07, 1.33)

Total effect: not reported

Not applicable

Not applicable

Rao et al. [36]

Smoking: low vs. high

Controlled direct effect: 1.5 (1.4, 1.5)

Total effect: 1.6 (1.4, 1.9)

Not applicable

Not applicable

Song et al. [37]

HOMA-IR:

Effect not mediated: 1.32 (0.95, 1.88)

Mediated effect: 1.22 (1.02, 1.49)

SHBG:

Effect not mediated: 1.97 (1.25, 3.10)

Mediated effect: 1.16 (1.03, 1.33)

E-selectin:

Effect not mediated: 1.56 (1.10, 2.21)

Mediated effect: 1.12 (1.02, 1.23)

Systolic blood pressure:

Effect not mediated: 1.61 (1.25, 2.16)

Mediated effect: 1.03 (1.01, 1.07)

Not reporteda

Not applicable

Xie et al. [38]

Not reported

Not applicable

Not applicable

  1. BCSS brief core schema scales; CI confidence interval; CVD cardiovascular disease; HOMA-IR homeostatic model assessment for insulin resistance; OC osteocalcin; SE standard errors; SHBG sex hormone-binding globulin
  2. aDespite allowing for interaction, only models assuming no interaction were adopted due to no significant interaction between any of the exposures and mediators was observed