Researchers involved in the Mayo Clinic Study of Aging reported earlier this year that more than 6 percent of Americans between ages 70 and 89 develop mild cognitive impairment every year. Also, the condition appears to affect men and those who only have a high school education more than women and those who have completed some higher education.

People with mild impairment are at the stage between suffering the normal forgetfulness associated with aging and developing dementia, such as that caused by Alzheimer's disease.

The study on which the findings were based, titled "The Incidence of MCI Differs by Subtype and is Higher in Men," was published in the Jan. 25 issue of Neurology, the medical journal of the American Academy of Neurology. It reported that 296 of the 1,450 study participants developed the condition, an incidence rate of 6.4 percent per year overall. Among men, the annual incidence rate was 7.2 percent, compared with 5.7 percent per year for women.

"While incidence rates for MCI have been reported previously, ours is one of the few studies designed specifically to measure the incidence of MCI and its subtypes using published criteria," says lead author Rosebud O. Roberts, of the Mayo Clinic Division of Epidemiology. "The statistically significant difference between incidence rates among men and women represents an important finding for those evaluating patients for MCI."

The study also looked in more detail at patients with cognitive impairment, dividing them according to whether they developed what's called amnestic MCI, in which the condition affects the memory domain, or non-amnestic MCI.

Similar to the overall results, the incidence rates for the two categories of impairment were higher in men than in women. In addition, the study found that study participants with only a high school education developed both at a higher rate than those with some higher education.

"Understanding the distribution of incident MCI by age, sex, and other demographic variables is critical to helping us understand the cause of the condition, as well as how to prevent MCI and its progression to full-blown, irreversible dementia," Dr. Roberts says. "This study advances our understanding of MCI and will help clinicians provide even better care for their patients, especially during initial evaluations."

People with mild cognitive impairment have mild problems with thinking and memory that don't interfere with everyday activities, although their forgetfulness is often apparent to them and their friends and family. While not everyone with MCI develops dementia, an estimated 5 percent to 10 percent do.

Symptoms of MCI include:

•Difficulty learning and remembering new information.

•Difficulty solving problems or making decisions.

•Forgetting recent events or conversations.

Taking longer to perform complex or difficult mental activities.

Mayo Clinic is a nonprofit medical center that also is involved in research and education for people from all walks of life.

For more information, visit www.mayoclinic.org/about/ and www.mayoclinic.org/news.