Mayo Clinic Study Shows Mild Cognitive Impairment More Common in Men and Older Elderly

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Less Common for Individuals with More Education

May 02, 2007 -- BOSTON -- In one of the largest studies of mental functioning in people 70 to 89 years old, Mayo Clinic researchers examined 1,953 people and found that the prevalence of mild cognitive impairment is higher in men, and that it is linked to age and to duration of formal education. Older elderly people had more mild cognitive impairment, and more-educated people had less mild cognitive impairment.

The results were presented May 2 in Boston at the annual meeting of the American Academy of Neurology, the world's largest professional group studying brain and nervous system functions in health and disease.

Significance of the Mayo Clinic Research

The Mayo Clinic study is the first to detail mild cognitive impairment traits in a large, general population. Specifically, it shows that:

-- Between ages 70-74 years, about one in 10 people of the study sample had mild cognitive impairment.

-- Between ages 85-89 years, about one in five people had mild cognitive impairment.

-- Of the 1,953 people followed, 326 (16.7 percent) had mild cognitive impairment. More than half of the mild cognitive impairment group were men (190).

-- As duration of formal education increased to 16 years or more in the study group, the prevalence of mild cognitive impairment declined to less than half that of study subjects with only nine or fewer years of education. Specifically, the prevalence of mild cognitive impairment was 8.9 percent for those with the most schooling versus 24.3 percent prevalence of mild cognitive impairment for those with the least schooling.

-- Mild cognitive impairment subjects were most commonly impaired in the memory domain. The next most commonly impaired domain was attention.

Ronald C. Petersen, M.D., Ph.D., who directs Mayo Clinic's Alzheimer's Disease Research Center, led the study. He explains the significance of the results: "On a population basis, the cognitive characteristics of people with mild cognitive impairment are not well known -- so we set out to determine both the prevalence of mild cognitive impairment, and determine its cognitive profile as a means of helping clinicians, families and public health officials manage mild cognitive impairment. The prevalence of mild cognitive impairment in the highest age range is significant and, when coupled with the 10 percent of the population that has dementia, leads to almost 30 percent of the population in this age range either having mild cognitive impairment or dementia."

About MCI and the Mayo Clinic Study

Mild cognitive impairment is a preliminary state of mental decline often described as pre-Alzheimer's disease. While mild cognitive impairment has been recognized in recent years as a distinct clinical entity, prior to this Mayo Clinic study, few other groups of investigators had characterized the specific cognitive abilities of patients in the general population in an effort to estimate mild cognitive impairment prevalence and nature of the impairment.

To assess the characteristics of mild cognitive impairment, Mayo researchers randomly sampled 1,953 people living in Olmsted County, Minn., who were 70 to 89 years old, and who had no evidence of dementia at the beginning of the study. Each participant received a three-part evaluation:

-- Interview. A nurse talked with the person enrolled in the study and with a relative or friend who could verify facts of the medical and family history. The nurse verified the medications the person was taking.

-- Assessment of memory, language, attention and visuospatial domains.

-- Mental status examination and a neurological exam performed by a neurologist.

Results were reviewed by a panel of specialists who then classified each person in the study as having normal cognition, mild cognitive impairment or dementia. Prevalence estimates of mild cognitive impairment were obtained while accounting for the stratified study design.

Collaboration and Support

The research team also included Rosebud Roberts,.; David Knopman, M.D.; Robert Ivnik, Ph.D.; Vernon Pankratz, Ph.D.; Bradley Boeve, M.D.; and Walter Rocca, M.D. Their work was supported by the National Institute on Aging and the Robert H. and Clarice Smith and Abigail Van Buren Alzheimer's Disease Research Program.

Source: Mayo Clinic