An under-represented and underserved population in trials: methodological, structural, and systemic barriers to the inclusion of adults lacking capacity to consent.

Measures needed to address under-representation include greater scrutiny of exclusion criteria by those reviewing study proposals, providing education and training for personnel who design, conduct, and review research, ensuring greater consistency in the reviews undertaken by research ethics committees, and extending processes for advance planning to include prospectively appointing a proxy for research and documenting preferences about research participation. Negative societal and professional attitudes towards the inclusion of adults with impaired capacity in research should also be addressed, and the development of trials that are more person-centred should be encouraged. Further work to conceptualise under-representation in trials for such populations may also be helpful.