Scientists have used brain scans to predict neurological decline in otherwise healthy people who have gone on to develop dementia. This could lead to screening programmes to detect the early signs of Alzheimer's disease.
In their experiments, researchers took 60 healthy people and gave them a battery of psychological and neurological tests. They were then followed for four years, had their brains scanned regularly and were given memory and cognition tests annually. Those who performed considerably worse in tests in later years had their brain scans retrospectively studied for any early signs of dementia.
"We don't have enough data, yet, to say that the brain scans can predict Alzheimer's disease," said William Jagust, a neuroscientist at the University of California at Berkeley and lead author of the paper, published yesterday in the Annals of Neurology. "However, the locations of the affected brain regions have been associated in other studies with Alzheimer's, so it's possible that we are picking up early signs of the disease."
Researchers found that the less efficiently parts of the brain used glucose, its main fuel, the more likely people were to get worse results in memory, language, spatial ability and judgment tests in later years. Using positron emission tomography (Pet) scans, Dr Jagust saw that some of his subjects, including the ones who later developed cognitive problems, used less glucose in the parietal and temporal lobes of the brain. All these are the same regions affected by Alzheimer's disease and people with mild cognitive impairment. TheMRI scans focused on the entorhinal cortex and hippocampus regions in the temporal lobe of the brain, areas that are involved in memory. Dr Jagust found that the smaller these regions of the brain were, the worse people performed in later years in memory tests. In the course of the four-year study, five people developed neurological problems and one was diagnosed with Alzheimer's.
"In a project of this size, it's not realistic to expect the brain scans to predict Alzheimer's," said Mary Haan, an epidemiologist at the University of Michigan. "But there is enough information to say that Pet and MRI scans can predict subsequent cognitive decline in a population of cognitively normal people."
"By the time people who are already sick are identified, it's often too late to slow down the progression of Alzheimer's," said Prof Haan. "By identifying early changes that could predict the development of dementia, it may also be possible to link those changes to primary risk factors that could be altered."
Dr Jagust said that there had been an explosion of research into the molecular basis of Alzheimer's disease. "That may lead to effective drugs to cure or prevent the disease, and those drugs would likely be more effective the earlier they are given. That has given a new urgency to research in predicting as early as possible those who will go on to develop Alzheimer's," he said.
According to the Alzheimer's Society, dementia affects more than 750,000 people in the UK, around 18,000 of whom are under the age of 65. One person in 20 over the age of 65 and one person in five over the age of 80 is affected and the numbers are increasing.