Why are older adults living with the complexity of multiple long-term conditions, frailty and a recent deterioration in health under-served by research? A narrative synthesis review of the literature.

Older adults living with the complexity of multiple long-term conditions (MLTC), frailty and a recent deterioration in health are under-served by research. As a result, current treatment guidelines are often based on data from studies of younger and less frail participants, and often single disease focused. The aims of this review were (i) to identify why older adults living with the complexity of MLTC, frailty and a recent deterioration in health are under-served by research and (ii) to identify strategies for increasing their recruitment and retention. Although a range of factors have been suggested to affect the participation of older adults with MLTC and frailty in research, this review shows that much less is known about the inclusion of older adults living with the complexity of MLTC, frailty and a recent deterioration in health. Researchers should focus on strategies that minimise participation burden for these patients, maintaining an adaptive and flexible approach, to increase their recruitment and retention. Future research should include qualitative interviews to provide further insights into how best to design and conduct research to suit the needs of this population group.