Simply getting older is not the cause of mild memory lapses often called senior moments, says a new study by researchers at the Rush Alzheimer's Disease Center, in Chicago.

The study, published in the Sept. 15 online issue of Neurology, the medical journal of the American Academy of Neurology, found that even the very early mild changes in memory that are much more common in old age than dementia are caused by the same brain lesions associated with Alzheimer's disease and other dementias.

"The very early mild cognitive changes once thought to be normal aging are really the first signs of progressive dementia, in particular Alzheimer's disease." says Robert S. Wilson, neuropsychologist at Rush University Medical Center. "The pathology in the brain related to Alzheimer's and other dementias has a much greater impact on memory function in old age than we previously recognized."

The study involved over 350 nuns, priests, and brothers who participated in Rush's Religious Orders Study and completed up to 13 years of annual cognitive testing. After death, the brains were examined for the lesions associated with dementia.

Researchers looked at the rate of change in cognitive function over time. The last four to five years of life showed a very rapid decline. The preceding years showed a much more gradual decline that would be described as normal aging.

As expected, pathologic lesions were related to the rapid decline, but researchers were somewhat surprised to find that they also were strongly predictive of the mild changes in cognitive function.

"Our study finds that Alzheimer's disease and related dementias are the root cause of virtually all loss of cognition and memory in old age. They aren't the only contributing factors; other factors affect how vulnerable we are to the pathology and to its effects. But the pathology does appear to be the main force that is driving cognitive decline in old age," Wilson says.

Recognizing that the earliest changes in memory are related to Alzheimer's pathology can lead to early diagnosis and will be critical information if a treatment is developed that can alter the pathologic course of the disease, he says.

The Rush Alzheimer's Disease Center is one of 29 Alzheimer's disease research centers across the country designated and funded by the National Institute on Aging, which provided funding support for the study. The center is dedicated to reducing disability due to Alzheimer's disease and other age-related conditions through research on the treatment and prevention of disease. Since 1985, the center has provided services to more than 5,000 Alzheimer's patients and their families through its outpatient clinic.