The timing and frequency of trial inclusion in systematic reviews of type 2 diabetes drugs was associated with trial characteristics

Objective: To determine whether certain trial characteristics are associated with faster or more frequent inclusion in systematic reviews for drug interventions in type 2 diabetes. Study Design and Setting: We examined trials included in systematic reviews published between January 1, 2007 and January 1, 2017. Primary outcomes were time between trial publication and first inclusion in a systematic review and frequency of inclusion in systematic reviews over the study period. Multivariable Cox proportional hazards and regression models quantified associations with funding source, number of participants, trial conclusion, and journal impact factor. Results: Among 668 trials, the median time to inclusion was 76.1 weeks. Time to inclusion was shorter for trials with industry funding (hazard ratio [HR] 1.39; 95% confidence interval [CI] 1.13–1.71), more participants (HR 1.26; 95% CI 1.17–1.36), and published in higher impact factor journals (HR 1.28; 95% CI 1.14–1.45). The median frequency of inclusion was three. Frequency of inclusion was greater for trials with industry funding (relative risk [RR] 2.36; 95% CI 2.11–2.64), more participants (RR 1.51; 95% CI 1.47–1.55), positive conclusions (RR 1.89; 95% CI 1.68–2.13), and published in higher impact factor journals (RR 1.13; 95% CI 1.08–1.18). Conclusion: Certain trial characteristics are associated with faster or more frequent trial inclusion in systematic reviews of type 2 diabetes.