“Alzheimer’s begins to affect the brain many years before patients are diagnosed with the disease,” Simon Lovestone, an Oxford University researcher and the senior author of the study, said in a press release. “Many of our drug trials fail because by the time patients are given the drugs, the brain has already been too severely affected. A simple blood test could help us identify patients at a much earlier stage to take part in new trials and hopefully develop treatments which could prevent the progression of the disease,” Lovestone added.
The researchers, led by scientists from King’s College London and the British company Proteome, reported their findings today in a paper published in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association.
While hailing the potential of the research, James Pickett of Britain’s Alzheimer’s Society cautioned that it “does not mean that a blood test for dementia is just around the corner. These 10 proteins can predict conversion to dementia with less than 90 percent accuracy, meaning one in 10 people would get an incorrect result. Therefore, accuracy would need to be improved before it could be a useful diagnostic test.”
The researchers analyzed blood samples from 1,148 people — 476 who had Alzheimer’s disease, 220 diagnosed with mild cognitive impairment (MCI) and 452 elderly people without dementia who served as a control group. They looked for 26 proteins previously linked to Alzheimer’s and found 16 that were strongly tied to brain shrinkage in either MCI or Alzheimer’s. A second set of tests using MRI brain scans showed that 10 of the proteins could predict whether the early memory loss would progress to Alzheimer’s within a year.
About 10 percent of those diagnosed with MCI develop dementia within a year — Alzheimer’s is the most common form of dementia. The rate of decline is measured by memory tests, but such tests can’t predict the future. Other studies show brain imaging and analysis of cerebrospinal fluid can predict dementia’s onset, but the latter is invasive and the former quite expensive.
While this is the largest study of blood bio-markers linked to Alzheimer’s, it is not the first. Another study of 525 patients reported in March in the Journal Nature Medicine found 10 fats in blood that predicted with 90 percent accuracy whether people with no signs of memory loss would develop MCI or Alzheimer’s in two to three years.
Both studies cautioned that further work should be done to see if the same results could be achieved with larger sample sizes — and that the approach should be tested on people of different ages and racial groups.
One question sometimes raised about early identification of people with Alzheimer’s is that some people may not want to know if they have it, given the fact that there is no cure.
On the other hand, knowing in advance could buy vital time for estate planning and enjoying life to the fullest before losing cognitive function.
Questions about stigma — and identity — come with Alzheimer’s testing, Jason Karlawish, a professor of medicine, medical ethics and health policy at the University of Pennsylvania, told NPR in March. “How will other people interact with you if they learn that you have this information?” he said. “And how will you think about your own brain and your sort of sense of self?”