Individual participant data meta-analyses (IPDMA): data contribution was associated with trial corresponding author country, publication year, and journal impact factor

Abstract

ObjectivesThe objectives were to determine the proportion of eligible randomized controlled trials (RCTs) that contributed data to individual participant data meta-analyses (IPDMAs) and explore associated factors. Study Design and SettingIPDMAs with ≥10 eligible RCTs were identified by searching MEDLINE, EMBASE, CINAHL, and Cochrane May 1, 2015 to February 13, 2017. Mixed-effect logistic regression was used to identify factors associated with data contribution. ResultsOf 774 eligible RCTs from 35 included IPDMAs, 517 (67%, 95% confidence interval [CI]: 63%–70%) contributed data. Compared to RCTs from journals with low-impact factors (0–2.4), RCTs from journals with higher impact factors were more likely to contribute data: impact factor 5.0–9.9, odds ratio [OR] 2.6, 95% CI: 1.37–4.86; impact factor: 10.0–19.9, OR: 5.7, 95% CI: 3.0–10.8; impact factor >20.0, OR: 4.6, 95% CI: 1.9–11.4. RCTs from the United Kingdom were more likely to contribute data than those from the United States (reference; OR: 2.4, 95% CI, 1.3–4.6). There was an increase in OR per publication year (OR: 1.05, 95% CI: 1.02–1.09). ConclusionThe country where RCTs are conducted, impact factor of the journal where RCTs are published, and RCT publication year were associated with data contribution in IPDMAs with ≥10 eligible RCTs.