Many people wrongly fear living into their 90s because they believe that they will suffer some kind of mental impairment such as Alzheimer's disease, according to a study reported in the Feb. 11th issue of Neurology.

Mayo Clinic researchers found that about half of those who are 90 years old and older have a strikingly sharp memory. Even those who do become memory impaired, as long as they do not have dementia, still remain relatively independent.

"Just because you're in your 90s does not mean you'll be living in a nursing home or developing dementia," said study author Dr. Bradley Boeve, a Mayo Clinic neurologist. "While there may be some decline in cognitive performance with age, dementia or Alzheimer's disease are not inevitable in all those living well beyond 90 years of age."

Boeve said the cognitive function of at least half of the people studied in their 90s was normal. He noted that some performed in the superior range on cognitive tests even when compared with much younger individuals.

The researchers also determined for the first time in this study that mild cognitive impairment (MCI), a condition that often progresses to Alzheimer's disease, does exist in those in their 90s.

Previously, the researchers had been uncertain whether the diagnosis of MCI could be made in a population of such advanced age, which has a proportionally greater degree of functional and mental decline.

This study was conducted through home visits in which a behavioral neurologist and a nurse performed neuropsychometric testing, functional assessments and comprehensive neurologic evaluations with 111 residents between the ages of 90-99 living in Rochester, Minn.

The researchers plan to continue their work studying this population, examining such factors as genetic and environmental commonalities among those who have lived to age 90 and above, and determining whether patients with MCI who progress to dementia have underlying Alzheimer's disease or some other disorder.

Other sources: Mayo Clinic, Neurology 2003;60:477-480