Importance .justify:after { content: ""; display:inline-block; width: 100%; } Recently, we showed that the elderly are significantly underrepresented in randomized controlled trials (RCT) in rheumatoid arthritis (RA) and osteoarthritis (OA). While this phenomenon has been detected in other fields as well, efforts by various international institutions to tackle the issue were without decisive success. Researchers might be cautious about including more elderly people because they fear reduced trial retention rates. .justify:after { content: ""; display:inline-block; width: 100%; } Objective .justify:after { content: ""; display:inline-block; width: 100%; } To evaluate whether the proportion of included elderly individuals (defined by an age of ≥65 years) is independently associated with trials’ retention rates. .justify:after { content: ""; display:inline-block; width: 100%; } Data Source .justify:after { content: ""; display:inline-block; width: 100%; } MEDLINE (via PubMed). .justify:after { content: ""; display:inline-block; width: 100%; } Eligibility .justify:after { content: ""; display:inline-block; width: 100%; } RCT on any intervention in RA or OA published in 2016 or 2017. .justify:after { content: ""; display:inline-block; width: 100%; } Outcome .justify:after { content: ""; display:inline-block; width: 100%; } Retention rate. .justify:after { content: ""; display:inline-block; width: 100%; } Critical Appraisal .justify:after { content: ""; display:inline-block; width: 100%; } We will not address any conclusion made by included RCT. Thus, we will not perform a formal risk of bias assessment. .justify:after { content: ""; display:inline-block; width: 100%; } Synthesis Methods .justify:after { content: ""; display:inline-block; width: 100%; } The proportion of elderly people is either directly abstracted from the research manuscript or estimated from an assumed truncated normal distribution. Multivariable meta-regression will explore whether the proportion of included elderly people is independently associated with trials’ retention rates, even after adjusting for trial duration. The model will include as covariates – apart from the proportion of elderly people and study duration - disease, type of intervention, region, sample size at enrollment, and the proportion of women. Additional models will explore whether the proportion of included elderly people is independently associated with trial retention rates when only drop-outs due to adverse events, resp. lack of efficacy are counted. .justify:after { content: ""; display:inline-block; width: 100%; }