A new study finds that memory loss may be a feature of aging independent of the plaque buildup that is widely thought to be the primary cause of Alzheimer's disease—and that natural memory loss appears to occur faster in men than in women.
Study explores age-related memory loss
The study, published in JAMA Neurology, examined 1,246 adults between ages 30 and 95. All took standard memory tests and had their brains imaged by PET and MRI scans. None had dementia.
Overall, both memory and brain size declined as subjects approached their mid-60s. However, few participants showed a buildup of the beta-amyloid protein—a plaque associated with Alzheimer's disease—prior to age 70. Researchers say the results suggest memory loss and brain shrinkage is a natural feature of aging, and that there may be approaches to studying Alzheimer's that do not target plaque buildup.
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Some of the participants at risk of developing Alzheimer's showed signs of plaque buildup at a younger age and a sharper increase after age 70. However, it did not result in more severe memory loss or decreased brain size. Jack called that finding "a little surprising."
"There seems to be a profound effect of aging, itself, on memory—independent of [the protein]," says Clifford Jack, a researcher who led the study at the Mayo Clinic. "We think that [amyloid] pathology tends to arise late in life, to accelerate a pre-existing decline in memory," he explains.
Gender makes a difference, study finds
One of the strongest predictors of memory loss was being male, the study found.
Although both men and women begin to see memory declines around age 30, male memory was significantly worse than female memory—especially after age 40. The researchers noted that the hippocampus, which controls memories, appears smaller in men than in women, especially after age 60.
"The men's hippocampus starts off a little bit above average in the young people in the study. But then it falls way below average in the older men as compared to the older women," says neurologist Charles DeCarli, who reviewed the study before publication.
One cause may be men's increased risk of cardiovascular problems, which has been linked to reduced cognitive function. Estrogen levels in women may also help preserve memory, Jack says (Norton, HealthDay, 3/16; McIntosh, Medical News Today, 3/17; LaMotte, CNN, 3/17).
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