Researchers in the US found sites of beta-amyloid plaque formation in the brains of people with Alzheimer's disease matched regions of elevated metabolic activity in those of healthy adults.
The team from Washington University School of Medicine said the findings could lead to early screening for risk of Alzheimer's before plaque formation begins.
How significant are the results?
Dr Andrei Vlassenko and colleagues examined metabolic activity in the brains of 58 individuals. The group comprised 33 healthy young adults, 11 people with dementia caused by Alzheimer's and 14 cognitively normal people with a high level of plaque deposition.
Researchers used PET scans to detect signatures of aerobic glycolysis, a form of energy production within the brain.
Previous studies have shown onset of dementia caused by Alzheimer's disease was associated with changes in brain metabolism in areas of the brain that are more active when healthy individuals are not engaged in focused, task-orientated behaviour.
Researchers compared scans of the three patient groups. They found a 'striking spatial correspondence' between sites of elevated aerobic glycolysis in healthy brains and sites of high amyloid-beta plaque deposition in the brains of patients with Alzheimer's.
The authors said the findings suggested a possible link between the brain functions fuelled by aerobic glycolysis and the onset of plaque formation that can cause Alzheimer's.
Could young people be screened for dementia?
Lead author Professor Mark Mintun said: 'Ideas for treatment could come out of this. If we can show that people are already making plaques, even in very small amounts, then it could lead to screening and intervening very early.'
The Alzheimer's Society said that although the study builds on knowledge of a link between brain activity and plaque formation, it did not prove a causal association.
Ruth Sutherland, interim chief executive at the charity, said: 'The presence of amyloid could be an early indication of Alzheimer's many years before the symptoms emerge. However, the study did not follow up with these people in old age so we cannot know whether this is the case.'
She added that more research in this area could improve understanding of dementia and could one day help scientists to diagnose dementia earlier.