Old age may not be to blame for becoming forgetful.  A new study by researchers at the Rush Alzheimer’s Disease Center finds that the very early mild changes in memory that are often referred to as senior moments 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.” said Robert S. Wilson, PhD, lead author of the study and a 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.”

Using data from the Religious Orders Study, a study of Catholic nuns, priests and brothers, researchers found that loss of cognition is initally slow and gradual, and then about four to five years prior to death, the rate of decline increases about four-fold.

It turns out the measures of Alzheimer’s pathology, the tangles, Lewy bodies and infarcts all contribute to the slow decline many years prior to death. Almost no gradual decline was seen in the absence of lesions.

The study suggests that Alzheimer’s disease and related dementias are the root cause of virtually all loss of cognition and memory in old age.

The study is published in the September 15, 2010 online issue of Neurology, the medical journal of the American Academy of Neurology.

Read the press release.

Watch of video of Dr. Wilson explaining the study.