Mild cognitive impairment: A way station along road to Alzheimer's

(Ronald Petersen, M.D., Ph.D., is the director of the Mayo Clinic Alzheimer's Disease Research Center. Below is an excerpt from an article he wrote that I thought you may find interesting.)

An unprecedented global shift toward an aging population has brought with it an increase in the occurrence of cognitive impairment such as Alzheimer's disease. With the baby boom generation beginning to arrive at the age of risk, this issue may be approaching crisis proportions that may bankrupt the health care system as we know it.

In the field of age-related dementia, there's likely a continuum from normal aging through a stage often called mild cognitive impairment on to dementia. The challenge for clinicians lies in assessing the question: "How much forgetfulness is too much?" Some incidental episodes of forgetfulness — "Where are my car keys?" — are likely common expressions of normal aging. However, when individuals begin to forget important information such as doctors' appointments and, most importantly, when they do this on a repeated basis, and when a person's friends and family begin to notice forgetfulness in the individual, it's time to seek medical attention.

A great deal of research in aging and dementia is now focused on mild cognitive impairment — a clinical condition in which people are more forgetful than they used to be, and more than they ought to be. And although their function around the community may be relatively normal, when these individuals seek a medical evaluation the degree of forgetfulness exceeds what would be expected for that person's age and education.

At Mayo Clinic in Minnesota, investigators are pursuing these issues in the Mayo Clinic Study of Aging. This project is a study over time of 2,000-3000 persons randomly sampled between the ages of 70- to 89-years old. At each annual visit, information is acquired, including mild cognitive impairment scans, blood samples for DNA and plasma proteins, historical data on cognitive and intellectual activities, dietary information, a quantitative assessment of gait, and a measure of olfactory functioning, which can be associated with degree of dementia in Alzheimer's.

The long-term goal of this project is to describe trajectories of successful aging, typical aging, and impaired aging from a cognitive perspective. Ultimately, we hope to identify a model that might be useful at predicting who is going to follow which of the three aging trajectories. When disease-modifying therapies become available, this model could help clinicians decide when and how to intervene with individual patients. It may well be that studies performed in Minnesota will inform the worldwide community about this pending crisis.

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