Wilson's first study was conducted on 174 individuals, whose memories were tested once a year from anywhere between 6 to 15 years before death. As a means of measuring changes, scientists looked for "plaques" and "tangles," hallmarks of Alzheimer's disease, on the surface of their brains.
"Memory and other cognitive decline may involve some biological changes in the brain specific to the end of life," Author Hiroko H. Dodge, PhD, with Oregon Health and Science University in Portland and a member of the American Academy of Neurology was quoted as saying.
The study revealed that there is a period of both thinking capacity and memory decline that occurs at about two-and-a-half years before death, where these cognitive functions experience an accelerated deterioration up to 17 times faster than before this terminal state.
While larger amounts of "plagues" and "tangles" were revealed to accompany an earlier onset of the terminal period, they were not revealed to affect the rate of memory decline within the period.
Wilson's second study tested 1, 076 individuals with an average age of 80. Participants' memories were tested once a year for roughly five years. In corroboration with the exam, participants also recorded on how often they took part in mentally stimulating activities such as reading, writing, and thinking games. Each individual's frequency regarding these activities was given a score from 1 to 5: one being the least, five being the most.
The study found a parallel between the amount of participation in mentally stimulating activities and mental capacity.
"The results suggest a cause and effect relationship: that being mentally active leads to better cognitive health in old age," Wilson was quoted as saying.
SOURCE: American Academy of Neurology, April 2012