One of the important questions asked around the time of the disastrous vaccine trial was whether the removal of these plaques from the brains of people with Alzheimer's disease actually resulted in any recovery of lost ability. The answer overall was little if any, just as clearing away the ruins of a city like Berlin or Dresden did not by itself reconstruct the city. In other words, treating Alzheimer's disease once dementia is already well established might be too late.

Dr Denise Park of the University of Texas was interviewed in February on the Today programme. Her team had scanned a large number of elderly people using an expensive and relatively new technique. This enables researchers to measure the amount of amyloid plaque in the brains of living people. Beta amyloid protein has long been considered one of the basic causes of Alzheimer's disease. The reason she was being interviewed was to describe the surprising results of her research: although 20 per cent of the subjects in her trial had large amounts of beta amyloid in their brain they were not displaying any signs of dementia.  

This lack of a neat correlation between the amount of beta amyloid and the severity of dementia has long been apparent to researchers, but I was astonished to see it entering the consciousness of popular science.

It is beginning to dawn on the researchers that even if an agent was found to be effective against the plaques or tangles it would probably need to be administered when these proteins begin to form in the brain and the evidence is that this happens up to 40 years before the onset of symptoms. Research has now moved in the direction of early detection and has mobilised an array of high-tech gadgetry directed at brain imaging and analysing cerebral spinal fluid for traces of the two offending proteins. In Sweden, for example, a person undergoing investigation for suspected dementia will routinely have a lumbar puncture in order to analyse the cerebral spinal fluid. Enhanced scans can also provide pictures not only of the detailed structure of the brain but also of how particular regions are functioning in terms of consumption of oxygen or glucose, and the presence or absence of beta amyloid.