The researchers studied 350 Catholic nuns, priests, and brothers who were given memory tests annually for up to 13 years, and after death, had their brains examined for lesions.
The study found that memory decline tended to be gradual before speeding up in the last four or five years of life.
Tangles and Lewy Bodies
Researchers say they found that strokes as well as protein accumulations called tangles and Lewy bodies seemed to be related to memory loss in older people.
They report that minimal gradual memory declines were seen in the absence of tangles, while Lewy bodies and strokes doubled the rate of gradual memory loss.
Tangles and Lewy bodies were found to be associated with rapid memory decline but explained only about a third of the memory loss.
“It appears these brain lesions have a much greater impact on memory function in old age than we previously thought,” study author Robert S. Wilson, PhD, of the Rush University Medical Center, says in a news release. “Our results challenge the concept of normal memory aging and hint at the possibility that these lesions play a role in virtually all late-life memory loss.”
The subjects, for up to 13 years, had memory tests that involved word recall, naming, verbal, number, and reading assignments, and all had agreed to autopsies so that their brains could be studied.
“Understanding how and when these brain lesions affect memory as we age will likely be critical to efforts to develop treatments that delay memory loss in old age,” Wilson says.
Lesions Cause Memory Loss
The researchers conclude that mild age-related declines in cognitive function are mainly the result of the lesions that traditionally are associated with dementia, but there are other causes as well.
They say their findings indicate that brain lesions associated with dementia are mainly responsible for gradual age-related cognitive decline that precedes dementia, Alzheimer’s disease, and related disorders.
The lesions, they write, apparently “have a much greater impact on late-life cognitive functioning than previously recognized.”
Better Understanding of Brain Aging Could Point to Treatments
The authors say that better understanding of individual differences of memory loss and early changes in the buildup of proteins may offer hope and new strategies for delaying the start of dementia’s symptoms.
The study is published in the Sept.15, 2010 online issue of Neurology, the medical journal of the American Academy of Neurology.