Beta-amyloid protein builds up in the brain in people with Alzheimer's disease and leads to memory loss and mood swings, along with other cognitive problems. But these physical changes begin long before signs of Alzheimer's start. So at what point does the build-up of the protein biomarker actually have an effect on people's cognition? Most studies have only involved older people, and researchers at the University of Texas at Dallas, including the Center for Vital Longevity, have set out to determine what the issues could be in a wider range of ages.
The team studied 137 people between the ages of 30 and 89, who were all healthy with normal levels of cognition. The levels of beta amyloid were measured using PET imaging, and each volunteer was tested for the gene for apolipoprotein E ε4, a known biomarker for Alzheimer's. Each person then sat for a number of tests designed to assess memory, reasoning and verbal ability.
In the study, the levels of beta amyloid generally increased with age, even through middle age. In a subgroup of people over 60, about 20% had increased levels of beta amyloid in their brains and were more likely to express APOE ε4. The higher levels of beta amyloid were linked with lower levels of cognition, although these changes were subtle and the people still scored normally on standard tests.
"Our findings suggest that subtle effects on cognition occur early," said principal investigator Dr. Denise Park, co-director of the Center for Vital Longevity and Distinguished University Chair in the School of Behavioral and Brain Sciences at UT Dallas. "These are important findings because imaging patients when they first show signs of very mild cognitive impairment could be essential to determining their risk of future disease."
The study shows that certain levels of beta amyloid don't have a significant effect on cognition, so another excuse will need to be found for middle-aged 'senior moments.' But on a more serious note, the increased levels in a specific subgroup could suggest the people who are at higher risk of Alzheimer's disease, as well as those who might benefit from early preventive medications to slow or halt the changes. Longer studies are under way as part of the Dallas Lifespan Brain Study, which is examining neural and cognitive aging across the entire adult lifespan.
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