In this article, we take the concept of evidence-based activism as a point of departure to understand how Alzheimer's disease (AD) associations have mobilised knowledge to re-articulate their role in the public sphere. We are specifically interested in political initiatives deployed by these organisations to shape the field of dementia care research, policy and practice in the last 5 years in the United Kingdom and Ireland. In both countries, the campaigns have emphasised the importance of developing and funding services and devices that mediate between the formal and the informal sectors of dementia care in order to support people living with dementia to stay at home for longer. Drawing on our analysis of documentary and interview data, our suggestion is that the transformation of dementia care into a 'matter of concern' is underpinned by AD organisations' harnessing, fostering, sponsoring and circulating of social research conventions and methodologies such as the survey or the interview. Our main claim is that social scientific techniques and ways of reasoning have been key in the production and maintenance of boundary relations between informal and formal care in dementia. Our work can thus be seen as integrated in a renewed interest in understanding the epistemic cultures of social research and its relationship with political institutions of contemporary societies.