Comprehensive geriatric assessment-where are we now, where do we need to be in the context of global ageing?

Comprehensive geriatric assessment (CGA) is the cornerstone of modern geriatric medicine and the framework around which conventional and new models of care for older people are developed. Whilst there are a substantial number of reviews synthesising the evidence on patient and service outcomes from CGA, as an intervention it remains poorly described. There is a lack of detail on how a CGA plan is coordinated, delivered and followed up, especially outside of acute care. This commentary reflects on the authors' experience of extracting data from 57 published studies on CGA. CGA as an intervention is akin to a 'black box' in terms of describing and measuring participants' interactions with CGA activity in terms of time, frequency and amount (dose) received. There is also a lack of detail on how newly established CGA teams become effective, interdisciplinary, high functioning and sustainable teams. The CGA knowledge-do gap persists with a need to draw from complex system theory and implementation science frameworks to better describe the intervention and understand the influence of the organisation and health service within which CGA is operationalised. Equally, the voice of older people, families and staff is critical in the conduct and evaluation of CGA, and how it evolves as a model to meet the growing needs of ageing populations.