Improving recruitment of older people to clinical trials: use of the cohort multiple randomised controlled trial design.

There is widespread evidence of under-recruitment of older people to research studies, notably randomised controlled trials of interventions. Study exclusion criteria, ethical dilemmas, patient preference, risk of bias and challenges for treatment comparisons are particular problems faced by researchers. This article describes how more widespread use of the cohort multiple randomised controlled trial (cmRCT) design in ageing research may help address many of these problems. The original key features of the cmRCT design are a large observational cohort of people with the condition of interest (e.g. frailty) with regular measurement of outcomes for the whole cohort. For each RCT eligible patients are identified and a random selection offered the trial intervention; their outcomes are compared with those eligible patients not offered the intervention. Relevant assents are obtained at baseline to enable future involvement in a range of potential trials. Where possible, the follow-up schedule is aligned with the key time points for assessment in future trials and includes the key baseline descriptors, and primary and secondary outcomes. The cmRCT approach also enables detailed observational and qualitative research for the chosen condition of interest, and might include the establishment of research biobanks to better align basic science, epidemiological, qualitative and clinical trial research.