Rates of Mild Cognitive Impairment Higher Than Expected

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By Steven Reinberg
HealthDay Reporter

MONDAY, July 28 (HealthDay News) -- The growth in the number of cases of mild cognitive impairment in the elderly population is outstripping earlier predictions, Mayo Clinic researchers report.

"The rate of new mild cognitive impairment cases, in this group, was considerably higher than anticipated," lead researcher Dr. Ronald C. Petersen said in a news release. "If we extrapolate Alzheimer's incidence rates to MCI, we would expect perhaps 1 to 2 percent per year, but our findings were substantially higher than that."

Petersen's findings showed new cases are now account for a rate of about 5 percent annually amongst the elderly.

He was scheduled to present the findings Monday at the International Alzheimer's Disease Conference, in Chicago.

For the study, Petersen's team collected data on 1,786 people aged 70 to 89 who participated in the Mayo Clinic Study of Aging. In 2004, all these people were cognitively normal.

The researchers found that after a year, 5.3 percent had developed mild cognitive impairment, which is the intermediate stage between normal aging and earliest Alzheimer's.

That rate of cognitive impairment increased with age, with about 3.5 percent of those aged 70 to 79 developing cognitive impairment and 7.2 percent of those aged 80 to 89 developing it.

Men were almost twice as likely to develop mild cognitive impairment compared with women, Petersen's team notes.

"These results underscore the urgency of developing new and better strategies to create disease-modifying therapies for Alzheimer's," Petersen said. "In addition, for public health purposes, we need to know how many people are cognitively impaired and potentially on the road to Alzheimer's."

Greg M. Cole, associate director of the Alzheimer's Disease Research Center at UCLA David Geffen School of Medicine, thinks these findings do not bode well for the future.

"The risk for Alzheimer's disease and dementia rises exponentially with age, so women have a higher risk of developing dementia and a higher prevalence of Alzheimer's in most studies simply because they tend to live longer," Cole said.

"Thus, it is somewhat surprising that men have higher incidence rates of the milder forms of cognitive decline, including 'amnestic mild cognitive impairment' that many believe is simply an early stage of Alzheimer's," he said.

This would seem to imply that men are protected simply by dying off before their spouses, Cole said. "The corollary is that when men live longer from new medical advances that fail to prevent Alzheimer's disease, society as a whole and men in particular will be more at risk for dementia."

Two additional reports that were to be presented Monday offer reasons for hope in potential new treatments for mild cognitive impairment and the prevention of amyloid plaques, a hallmark of Alzheimer's, from forming in the brain.

In the first report, results of a trial of a new drug that targets abnormal changes in a protein called tau that lead to mild cognitive impairment found the drug improved a variety of measures of memory.

In the study, Dr. Donald Schmechel, a geriatrics professor at Duke University Medical Center, and colleagues tested the nasal spray, AL-108, on 144 men and women, 55 to 85 years of age, who had mild cognitive impairment.

After 16 weeks, there was a 62.4 percent improvement on tests of memory among those receiving the drug, the researchers report.

"Twelve weeks of AL-108 treatment given intranasally by spray resulted in a statistically significant, dose-dependent and durable improvement on measures of short-term memory, including visual, verbal, and auditory working memory, which is a type of memory function that deteriorates throughout the progression of Alzheimer's," Schmechel said in a statement.

In the second report, Michal Schnaider Beeri, from the Mount Sinai School of Medicine in New York City, and colleagues examined the brains of 124 people with diabetes and 124 people without the disease.

The researchers found that diabetics taking insulin, along with other glucose-lowering drugs, had as much as 80 percent fewer amyloid plaques compared with other diabetics and nondiabetics.