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Study Shows Global Rate of Mild Cognitive Impairment Is Similar to U.S. Rate
By Charlene Laino
WebMD Health News
Reviewed by Laura J. Martin, MD
July 22, 2011 (Paris) -- Mild cognitive impairment (MCI) is relatively common, affecting between 10% and 20% of older adults in the U.S. and four Western European countries, new data suggest.
The global perspective on MCI -- presented for the first time at the Alzheimer's Association International Conference -- also showed that major risk factors for developing MCI are older age, diabetes, stroke, obesity, and the presence of the ApoE4 gene variant that has been linked to Alzheimer's.
MCI involves problems with memory or other cognitive skills that are noticeable to the affected person and those around him, but not serious enough to interfere with daily life.
Research has shown that people with mild cognitive impairment are at increased risk of developing Alzheimer's disease within a few years. But not everyone who gets a diagnosis of MCI goes on to develop Alzheimer's.
MCI: The U.S. View
In the U.S. study of more than 1,600 people aged 70 to 89 who had no cognitive problems, about 7% per year developed MCI, says Ronald Peterson, MD, PhD, professor of neurology at the Mayo Clinic College of Medicine in Rochester, Minn.
Also, 10% of people per year who developed MCI went on to develop dementia, he says.
But the patients were only followed for about four years, Peterson says. "Based on the data we have, we would expect about 80% to convert from MCI to dementia if they were followed longer, for 10 years," he tells WebMD.
MCI: The Global View
In addition to the U.S. study, researchers at the MCI symposium presented data on more than 30,000 people aged 65 and older from Germany, Great Britain, Sweden, France, and Australia.
The prevalence of MCI in Australia was higher than in the other countries, affecting over 35% of people, but that's probably because the researchers used a less stringent definition of the condition, Peterson says.
If the same definition were used as in the other countries, the prevalence was closer to 10%, he says.
Henry Brodaty, MD, DSc, professor of aging and mental health at the University of New South Wales in Sydney and moderator of the symposium, tells WebMD that the findings from the six studies were more similar than dissimilar.
That consistency promotes confidence in the findings, he says.
These findings were presented at a medical conference. They should be considered preliminary as they have not yet undergone the "peer review" process, in which outside experts scrutinize the data prior to publication in a medical journal.