A new Mayo Clinic (MCI) study shows that the fears of many related to living into one's 90s and beyond -- getting lost in your own neighborhood; losing the ability to take care of financial affairs; having a driver's license revoked; ending up in a nursing home -- are in many cases unfounded.

This research, to be published in the February 11 issue of Neurology, http://www.neurology.org/, demonstrates that for many age 90 and above, memory can be strikingly sharp even up to one century of age. The researchers found a significant proportion of the nonagenarians, or people 90-99 years old, to be free of Alzheimer's disease or other forms of dementia. Others became memory impaired, but without full dementia, allowing them to remain relatively independent.

"Just because you're in your 90s does not mean you'll be living in a nursing home or developing dementia," says Bradley Boeve, M.D., Mayo Clinic neurologist and lead author of the publication.

The researchers interpret the testing results as positive news for those dreading mental and functional loss in their advanced years. Says Dr. Boeve, "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.

"At least half of these people looked pretty normal," says Dr. Boeve. "In fact, some performed in the superior range on cognitive tests even when compared with much younger individuals."

Ronald Petersen, M.D., Mayo Clinic neurologist and another publication author, points out that those who have normal cognitive function at age 90 or above might be mistaken for someone who is impaired, simply by virtue of age.

"Many times, adult children take over for their aging parents even if they're normal, because of frailty or because the children feel they should do it," says Dr. Petersen. This study indicates that many nonagenarians can function quite well independently.

Mayo Clinic 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.

"We didn't really know if we could tease out this early impairment stage in this age group because so many have some degree of cognitive impairment and/or are receiving assistance from family or friends," says Dr. Boeve.

Nonagenarians are less well studied than other age groups, and normal cognitive aging has not been fully defined for this age range. Thus, the researchers first wanted to determine whether testing for dementia, Alzheimer's disease or pre-Alzheimer's conditions could even be done in this age group: Could they use the same criteria as with younger people? Would most of those in their 90s be leaning toward dementia anyway, making it hard to determine normalcy?

"Despite their advanced age, presence of other medical problems, use of medications and assistance by relatives and friends, we were able to identify people who were cognitively normal, had mild cognitive impairment or had dementia," says Dr. Boeve.

The other question the researchers wanted to answer was whether MCI in those ages 90-99 had features similar to those of a younger person with MCI. The answer: yes.

"Those with MCI did poorly on memory studies but did pretty well on tests assessing global brain functioning," says Dr. Petersen. "The fundamental principle of MCI is that a person is functionally more like normal, but in the area of memory is more like those with dementia. People can become cognitively impaired but not have full dementia."

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 of Rochester, Minn., ages 90-99. All are participants in the Mayo Oldest Old Study, which is supported by the Alzheimer's Association and the National Institute on Aging.

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.