Even if you're 80 years old, you don't have to think that the risk of Alzheimer's disease is higher than that of a 75-year-old just because of that. New research suggests that the situation is much more complicated than that.
The findings suggest that the rate at which Alzheimer's-related amyloid plaques are formed in the brain is what matters more than age.
Our findings are consistent with multiple studies that show that it takes decades for amyloid buildup in the brain to form," said Dr. Oscar Lopez, a professor in the Department of Neurology at the University of Pittsburgh and lead author of the study.
His team's findings were published Dec. 22 in the journal Neurology.
Neuroscientists have long known that the slow but steady accumulation of amyloid plaques in brain tissue is a hallmark of Alzheimer's disease, although whether or not it actually causes the disease remains controversial.
It is true that the incidence of dementia increases with age, but is age alone the key factor?
To find out, Lopez's team examined the brain of 94 participants who were 85 years old at the time and had been followed for 11 years when they participated in the study, or until they died. During this time, each of them underwent two positron emission tomography scans of their brains.
The researchers compared the levels of amyloid buildup shown in the scans with the scans of a younger group of patients (in their 60s) observed in previous Australian trials.
As expected, the accumulation of amyloid plaques increased over time, regardless of how much of the protein had penetrated into the brains of participants when they joined the Pittsburgh study.
Lopez's team reported that plaques appear to accumulate faster in people in their 80s compared to people in their 60s.
In the Lopez trial, no Alzheimer's patients were found without plaque buildup in the brain, confirming the important role that plaque plays in the disease.
On top of that, when plaque buildup in the brain begins, it seems to be the key to when dementia occurs.
The Pittsburgh team found, for example, that people who already had amyloid buildup at the time of their PET scan (they took part in the study at age 80) developed dementia two years earlier than those who didn't have early buildup.
Ultimately, Lopez's team adds, the long-term association with amyloid buildup and other brain health indicators with dementia is greater than the short-term growth of plaques themselves.
Lopez said at the university's news conference that this is in line with other studies that have found that "the buildup of amyloid 'takes decades to form and occurs in the context of other brain pathologies.'"
Lopez said the study from the Pete Alzheimer's Disease Research Center will provide an important scientific basis for future primary prevention**. "The timing of the emergence of these pathologies is critical and will be critical for the implementation of future preventive measures. Lopez said.
*: University of Pittsburgh press release, December 22, 2023.
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