Table 3 Reporting recommendations for mediation analysis with a time-to-event outcome

Objectives

State whether mediation analysis(es) is/are exploratory or hypothesis-based

Methods

Specify criteria or statistical tests used to assess mediation, with references

Was the goal to categorize mediation as absent, partial or complete, or to estimate exact values for direct and indirect effects?

Detail how exposure, mediator and outcome variables were defined and measured

Detail when exposure, mediator and outcome variables were measured

Describe statistical models used for the mediator(s) and outcome(s), and any assumptions underlying use of such models (e.g. proportionality, rare outcome assumption for Cox Proportional Hazards models)

State whether interaction between exposure and mediator was considered, and how

Reference any software programs used for mediation analysis

If relevant for exposure, mediator, and outcome being considered, state how the following were addressed:

- clustering or repeated events

- competing risks

Describe assumptions underlying mediation analysis, and methods used to address these (e.g.: randomisation, regression, weighting, stratification, sensitivity analysis)

Results

Report measures of mediation effect (indirect effect or proportion mediated) accompanied by 95% confidence intervals

Report p-values for mediation hypothesis testing

Discussion

Discuss limitations of causal inference based on mediation analysis results, including whether underlying assumptions were met

Discuss magnitude and direction of any potential bias