The brains of all people with Alzheimer’s disease accumulate amyloid, a protein which clumps together to form toxic plaques. This assumed role of amyloid in the development of Alzheimer’s and attempts at its removal have become focal points for dementia research strategies.

The ART study showed immunisation caused a long-term reduction in amyloid in the brain and a variable degree of plaque removal compared with non-immunised control patients.

Contrary to predictions, removal of amyloid plaques did not result in an improvement in cognitive function or survival. Several patients with complete plaque removal deteriorated severely.

The previous consensus among dementia scientists – that removing amyloid plaques is key to defeating Alzheimer’s – may now need to be rethought.

Lead researcher Prof Clive Holmes of the University of Southampton said: ”Our results suggest that brain deterioration can occur in Alzheimer’s despite the removal of plaques. It may be that these toxic plaques trigger the neurodegeneration but don’t have an ongoing role. This study opens up numerous avenues for further research.”

Rebecca Wood, Chief Executive of the Alzheimer’s Research Trust, said: “This is groundbreaking research, and a leap forward in our understanding of Alzheimer’s disease. It is disappointing that anti-amyloid treatments did not prevent the disease’s progress, but we still need to do more research into whether earlier removal of this initial ‘motor’ of the disease could slow its progression. These findings underline the need to take a variety of research approaches in a multi-pronged attack on this devastating disease.

“The Alzheimer’s Research Trust is funding further research into the toxic nature of amyloids at several universities. Unfortunately Alzheimer’s research is pitifully under-funded in the UK. ART has to reject two out of every three grant applications from scientists. We’re urgently scraping for every penny.”