Included study characteristic | Result |
---|---|
Funding source, n (%) | |
Government | 113 (76) |
Foundation | 37 (25) |
Hospital | 6 (4) |
Industry | 6 (4) |
University | 4 (3) |
Professional association | 1 (< 1) |
None stated | 13 (9) |
Study design, n (%) | |
Cohort | 131 (88) |
Randomised Controlled Trial | 8 (5) |
Case-cohort | 5 (3) |
Case control | 4 (3) |
Cross-sectional | 1 (< 1) |
Type of analysis, n (%) | |
Confirmatory/Hypothesis-based | 72 (48) |
Exploratory | 74 (50) |
Not able to infer | 3 (2) |
Mediation analysis is primary aim of study, n (%) | 69 (46) |
Multiple mediators tested, n (%) | 76 (51) |
Type of mediator, n (%) | |
Continuous | 60 (40) |
Binary | 56 (38) |
Categorical | 25 (17) |
Interval/Ordinal | 25 (17) |
Latent | 8 (5) |
Most common content of mediatora, n (%) | |
Physiologic (e.g. blood pressure, heart rate, weight) | 34 (23) |
Psychological/psychiatric | 32 (21) |
Lifestyle (e.g. alcohol, smoking, nutrition, exercise, sleep) | 31 (21) |
Biomarker (blood test results) | 24 (16) |
Health | 17 (11) |
Comorbidity | 13 (9) |
Treatment | 8 (5) |
Functioning | 8 (5) |
Socioeconomic | 8 (5) |
Environment | 6 (4) |
Reproductive | 2 (1) |
Most common outcomes, n (%) | |
New medical condition or exacerbation of an existing condition | 68 (46) |
All-cause mortality | 48 (32) |
Cause-specific mortality | 21 (14) |
Disability or sick leave | 6 (4) |
Causal diagram included, n (%) | |
Causal steps/change in coefficient (n = 87) | 22 (25) |
Counterfactuals (n = 32) | 16 (50) |
SEM/path (n = 23) | 18 (78) |
Product of coefficients (n = 6) | 3 (50) |
Cannot infer (n = 1) | 0 (0) |
Sample size, median (IQR) | 3345 (637–16,061) |
Power/sample size, n (%) | |
Calculation | 1 (< 1) |
Consideration | 3 (2) |
Method of mediation analysis, n (%) | |
Causal steps, including Baron-Kenny | 41 (28) |
Change in coefficient in a single regression | 46 (31) |
Counterfactuals | 32 (21) |
SEM/path | 23 (15) |
Product of coefficients | 6 (4) |
Cannot infer | 1 (< 1) |
Statistical tests for no mediation/indirect effect, n (%) | |
Sobel | 7 (5) |
Other product test | 14 (9) |
Difference test | 2 (1) |
Z-test of mediated proportion | 1 (< 1) |
Joint significance test | 1 (< 1) |
Olaf & Finn test | 1 (< 1) |
Type of time-to-event model, n (%) | |
Cox proportional hazard | 114 (77) |
Additive hazard | 10 (7) |
Linear | 7 (5) |
Discrete time survival model | 6 (4) |
Failure time/parametric survival | 5 (3) |
Marginal structural model | 3 (2) |
Log linear Poisson | 1 (< 1) |
Quantile regression | 1 (< 1) |
Cannot infer | 5 (3) |
Specific mediation software mentioned, n | |
Causal steps/change in coefficient | |
SAS “mediate” macro | 2 |
PRODCLIN | 1 |
Counterfactuals | |
R | 8 |
R “mediation” | 2 |
SAS | 1 |
SAS “mediate” macro | 1 |
STATA “medeff” | 1 |
SEM/path | |
Mplus | 13 |
SAS | 1 |
STATA mediation package | 1 |
LISREL | 1 |
Competing risks considered, n (%) | 4 (3) |
If clustering of data, was this addressed in the analysis? n (%) | |
Not multilevel | 114 |
Yes | 19 (54) |
No | 8 (23) |
Cannot determine | 8 (23) |
Cox models, outcome frequencyb, n (%) | |
> or equal to 5% | 74 (65) |
> or equal to 10% | 55 (48) |
Rare outcome limitation for Cox model mentionedb, n (%) | 8 (7) |
Temporal separation clearly defined, n (%) | |
Yes | 37 (25) |
Overlap exposure and mediator | 89 (60) |
Overlap mediator/outcome | 7 (5) |
Cannot determine | 19 (13) |
Acknowledged as a limitation | 20 (13) |
Mediation assumptions (or limitation) stated, n (%) | |
No unmeasured confounding of exposure/outcome | 29 (19) |
No unmeasured confounding of mediator/outcome | 29 (19) |
No unmeasured confounding of exposure/mediator | 22 (15) |
No exposure-dependent confounding of mediator-outcome | 17 (11) |
Accurate measurement of mediator | 31 (21) |
Interaction between exposure and mediator considered/tested, n (%) | 46 (31) |
Method to address confounding of exposure (more than one can be used), n (%) | |
Regression/modelling | 137 (92) |
Stratification/restriction | 14 (9) |
Randomisation | 6 (4) |
None | 9 (6) |
Method to address confounding of mediator (more than one can be used), n (%) | |
Regression/modelling | 138 (93) |
Weighting | 13 (9) |
Stratification/restriction | 13 (9) |
Matching | 1 (< 1) |
None | 10 (7) |
Sensitivity analysis related to mediation analysis, n (%) | |
Any | 25 (17) |
Confounding | 8 (5) |
Accurate measurement/specification of mediator | 7 (5) |
Temporal sequence assumption | 6 (4) |
Testing a combined mediator or all mediators in same model | 5 (3) |
Interaction/moderation | 2 (1) |
Measures of mediation reported, n (%) | |
Causal steps/change in coefficient method (n = 87) | |
Indirect effect | 7 (8) |
Proportion mediated | 52 (60) |
Counterfactuals (n = 32) | |
Indirect effect | 29 (91) |
Proportion mediated | 22 (69) |
SEM/path (n = 23) | |
Indirect effect | 16 (70) |
Proportion mediated | 5 (22) |
Other (n = 7) | |
Indirect effect | 3 |
Proportion mediated | 4 |
Measures of precision reported, n (%) | |
Causal steps/change in coefficient (n = 87) | |
Indirect effect confidence interval | 6 (7) |
Proportion mediated confidence interval | 17 (20) |
Statistical test p-value or equivalent | 10 (11) |
Counterfactuals (n = 32) | |
Indirect effect confidence interval | 29 (91) |
Proportion mediated confidence interval | 14 (44) |
SEM/path (n = 23) | |
Indirect effect confidence interval | 15 (65) |
Proportion mediated confidence interval | 2 (9) |
Statistical test p-value or equivalent | 4 (17) |
Other (n = 7) | |
Indirect effect confidence interval | 3 |
Proportion mediated confidence interval | 3 |
Statistical test p-value or equivalent | 2 |