Re-Analyses of 8 Historical Trials in Cardiovascular Medicine Assessing Multimorbidity Burden and Its Association with Treatment Response

Objective: The purpose of this study was to examine the multimorbidity burden of clinical trial participants and assess its association with treatment response. Methods: We conducted a reanalysis of patient level data. There were 29,954 participants from 8 clinical trials containing 11 comparisons between an intervention and control condition. Patients were classified by Charlson Comorbidity Index (CCI) score. The primary outcomes were the primary study endpoints as originally specified for each trial. A Cox model that included the CCI score groups, the randomized group, and their interaction, was used to compare the primary outcome between randomized groups. The interaction term between randomized group and comorbidity index allowed the treatment effect to differ by level of comorbidity index and comprised the primary effect of interest. Hazard ratios and risk differences were reported for all comparisons. Results: The mean CCI scores of trial populations ranged from 2.1 to 3.9 points, and the percentage of patients with scores ≥5 from 3% to 39%. Tests of interaction terms in models yielded P values ≤.10 for 4/11 comparisons and ≤.05 for 2/11 comparisons. In 3 additional comparisons, potentially important treatment variation on an absolute scale was observed despite interaction tests with P values >.10 on the relative scale. Conclusions: These trials were mainly composed of patient populations with CCI scores ≤4. Despite this, biologically plausible treatment interactions were commonly suggested. These results are hypothesis generating; confirmation of results would require larger studies or studies targeted specifically toward patients with higher levels of multimorbidity.