It is reasonable to assume that a lifetime of intellectual stimulation bodes well for cognitive abilities as we age. But scientists have wondered if lifelong learning might actually slow down some of the physical hallmarks of Alzheimer’s disease, such as the amount of beta-amyloid in the brain or the size of the hippocampus. New research from Harvard University scientists published in Neurology suggests that while a lifetime of intellectual stimulation improves the chances that a person will still be cognitively fit as an older adult, it probably doesn’t reduce the physical changes in our brains that can lead to Alzheimer’s disease.
In this new study, scientists asked 186 healthy older adults about the extent of cognitive activity that they’d engaged in through their life. Participants then underwent neuropsychological testing to characterize their current cognitive health. They were each given MRIs to measure the size of their hippocampus (which can shrink with age and Alzheimer's disease) and the ability of their brains to use glucose (which can decline with age and Alzheimer's). They were also given PET scans to measure the amount of beta-amyloid in their brains, which can accumulate with age and is a hallmark of Alzheimer's disease.
On average, the more cognitively enriched a person’s life had been, the more cognitively fit they were as an older adult. This also correlated with higher IQ and a greater level of education. Not too surprising. However, a lifetime of cognitive enrichment did not appear to reduce beta-amyloid, improve how the brain used glucose, or slow the shrinking of the hippocampus.
These findings suggest that a lifetime of cognitive activity leads to cognitive vitality in old age through mechanisms that are independent of the biology that drives Alzheimer’s disease. And possibly, no amount of learning or cognitive enrichment can slow down the deposition of beta-amyloid in the brain, although this is still up for debate. While at least one past study has yielded similar findings, another study did find an association between a cognitively enriching lifestyle and lower brain beta-amyloid.
Interestingly, this new study did not find any difference in people who carry the APOE4 gene, the greatest genetic risk factor for Alzheimer’s disease. However, a prior study reported a lifetime of cognitive activity lessened the detrimental impact of the APOE4 gene, resulting in lower levels of brain beta-amyloid.
Cognitive stimulation and education are important factors in building cognitive reserve, which is likely critical for maintaining cognitive vitality as we age. There is mounting evidence that a strong cognitive reserve may delay the onset of Alzheimer’s symptoms, even if it turns out not to directly impact the biology of Alzheimer’s disease, as this study suggests. So take those first steps and engage with your friends, join that book club, or enroll in that class you’ve been talking about. Your brain will thank you.
Photo: Jay Baker, Maryland GovPics
Aaron Carman, PhD, was previously the Assistant Director of Aging and Alzheimer's Prevention at the Alzheimer's Drug Discovery Foundation. Dr. Carman received his doctorate in microbiology and molecular genetics from The University of Texas Health Science Center at Houston.
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