The observational studies could not adjust for time dependent imbalance of severity: timing of return of spontaneous circulation is a determinant of both outcome and treatment (those who rapidly respond to initial resuscitation procedures would have a higher chance of survival and a lower chance of being given of adrenaline).
10 Their statistical models including only time independent covariates, however, could not appropriately adjust for time dependent imbalance.
Thus, a study using marginal structural models that adjust for time dependent confounding would be clinically relevant.
Models were adjusted for time-dependent covariates that were statistically associated with either the exposure or response.
The results are purely descriptive and were not adjusted for time-dependent changes in medication prescription and incident comorbidity.
This effect was only apparent when using a MSCM that adjusted for time-dependent confounding by systolic blood pressure and differential loss to follow-up, not when a standard Cox model was used.
Thus, most of the observed effect on glycaemia progression was ascertained through an effect on HbA1c; subsequent analyses focused on that but also adjusted for time-dependent changes in diabetes drug intensity.
Finally, we adjusted for time-dependent variables reflecting cumulative use of other drugs, anti-TNF inhibitors, other biologics, COXIBs, NSAIDs, and systemic steroids during the follow up, and binary indicators of anti-TNF, MTX, other DMARDs, COXIBs, NSAIDs, and systemic steroid use during the period of 1 year before cohort entry.
Unlike standard regression models, MSMs can adjust for time-dependent observed confounders while avoiding the bias due to the direct adjustment for covariates affected by the treatment.
