My mother is 89 years old and suffers from advanced dementia so I'm perhaps more interested than most of you in new information about the aging brain. Having said that, I find fascinating the results of a recently published study published in the August 27, 2008, online issue of Neurology® - the medical journal of the American Academy of Neurology.

The study documents 30 years of testing of people's mental skills from age 70 to death. The study involved 288 people with no dementia who were followed from age 70 to death, with an average age at death of 84. The participants' mental skills were measured up to 12 times over a period of 30 years, and they were evaluated to make sure they had not developed dementia.

"These changes are different and separate from the changes in thinking skills that occur as people get older," said study author Valgeir Thorvaldsson, MSc, of Goteberg University in Sweden. "We found accelerated changes in people's mental skills that indicated a terminal decline phase years before death."

For instance, perceptual speed - measured by how quickly one can compare figures - begins declining 15 years before death. Spatial ability - everyday tasks such as finding one's way in the environment and learning the layout of a new environment - starts declining eight years before death. And verbal ability starts declining about six-and-a-half years before death.

Thorvaldsson noted that verbal abilities declined sharply in the terminal phase and did not decline significantly due to age only. "This indicates that people remain stable in their verbal abilities unless they are experiencing disease processes that also increase their mortality risk," he said. "A change in verbal ability might therefore be considered a critical marker for degeneration in health in older people."

How much longer will I live? While not frequently verbalized, this question is in all of our minds and one would assume that it's much more prevalent in those of advanced age. As I see it, this study's uniqueness lies in identifying specific declines in mental skills as markers of life expectancy.