High levels of a blood protein called clusterin are linked to the development of Alzheimer’s disease, scientists said on Monday - a finding which could pave the way for doctors to detect the disease before it takes hold.

Researchers from the Institute of Psychiatry at King’s College London said that while doctors are around 5 years away from being able to use the discovery for a test to identify future Alzheimer’s sufferers, it was a big step along the way.

Alzheimer’s is the most common form of dementia - a brain-wasting condition that affects around 35 million people around the world - and despite decades of research, doctors still have few effective weapons against it.

Drugs can relieve some of the symptoms for a while, but patients gradually lose their memories, their ability to navigate and understand the world, and to care for themselves.

This research team used a technique called proteomics, which analyses proteins, to conduct two “discovery phase” studies in 95 patients and found that clusterin appeared to be linked with the early signs of Alzheimer’s. The findings were published in the Archives of General Psychiatry journal.

“We found that this clusterin protein was increased in blood as much as 10 years before people had the signs of Alzheimer’s disease in their brains,” said Simon Lovestone, who led the study. “And even when they had signs of disease in their brains, they still had no clinical signs of the disorder - so this suggests that this is a really, really early change that occurs in people who are going to get the disease.”

Lovestone said it was important to stress there was still a lot more work to do before a test could be used by doctors in clinics, but said such a technique may in future become part of a range of tests to find people with early signs of the disease.

The number of dementia sufferers is expected to balloon in future decades as populations around the world age. Alzheimer’s Disease International predicts numbers will almost double every 20 years to 66 million in 2030 and over 115 million in 2050.

“We think this is the first step towards finding a prodromal or preclinical test for the disease,” Lovestone said. A prodromal test is one that can detect very early signs of a disease before any specific symptoms are showing.

“If I look towards the future, such tests might be used as part of a staging process. I can imagine people first having a blood test and then those people who have high levels of clusterin might go on to have more intensive investigations.”

After their initial study in 95 patients, the researchers then studied clusterin levels in around 700 people, including 464 with Alzheimer’s disease, and found a link between higher levels of the protein and severity of disease, rapid progression of the condition and atrophy in the brain area known as the entorhinal cortex, which plays a role in memory.

Lovestone said the next step - which should take about a year - would be to develop a better test, since the one they used for the study would not be suitable for use in clinics.

“Once we’ve then designed the better test, we need to look at it in larger groups of people to see if our results are replicated,” he said. “That whole process will take between three to five years.”

SOURCE: Archives of General Psychiatry, July 5, 2010.