Strategies to improve research participation by older people with cognitive impairment: a systematic review

Older people with cognitive impairment are unrepresented in clinical research. Our objective was to review evidence for strategies to support their research inclusion and participation. Systematic review of published reports of inclusion and participation strategies for older people with cognitive impairment in clinical research (PROSPERO CRD42020212092). Five databases were searched September 2020, March 2023 and April 2024. Screening, full text review and data extraction were independently performed. Risk of bias was assessed using Scottish Intercollegiate Guidelines Network Methodology Checklists. Outcomes were participant characteristics, recruitment and consent processes, retention, experience, involvement of others, adverse events, and other reported outcomes. Of 4564 identified sources, 12 studies were included. Nine compared recruitment strategies; three examined consent processes. Of 4,208 participants (mean age 78.3 years), 61% were female. Median (interquartile range) monthly recruitment rate was 10.3 (5.6-14.8). Participants had mild cognitive impairment, dementia and/or delirium and two-thirds of studies involved proxies or study partners. Community outreach or population screening had higher recruitment compared to primary care referral and/or screening. Formal capacity and consent methods achieved lower rates of consent compared to informal. A memory and organisational aid increased participants' ability to provide informed consent compared to standard assessment. Few studies reported participants' or recruiters' subjective experience, and no studies reported participant retention or adverse events. Targeted, tailored and multi-pronged recruitment and consent strategies to support inclusion of older people with cognitive impairment appear promising. Higher quality studies are needed to confirm this finding.