Men are more likely than women to have problems with memory and other thinking skills, symptoms considered to be an early stage of dementia, research suggests.

The new study, to be presented at an annual meeting of the American Academy of Neurology in Chicago this week, expands the field of research on aging and memory into a touchy arena — cognitive differences among men and women. Forgetfulness linked with aging, or just a frenzied day, is normal. Say, you misplace your car keys or wallet, or you can't remember where you parked the car. Red flags should pop up when you start forgetting things you normally remember, and on a routine basis, such as weekly appointments, doctors say. These are signs of so-called mild cognitive impairment (MCI), which can lead to dementia.

People with mild cognitive impairment are three to four times more likely than others to develop Alzheimer's disease, according to the Mayo Clinic. Considered the most common form of dementia, Alzheimer's is a neurological disorder that affects your ability to think, speak, reason, remember and move.

The recent findings come from a study of nearly 2,000 residents of Olmsted County, Minn., who ranged in age from 70 to 89. Dr. Rosebud Roberts of the Mayo Clinic in Rochester, Minn., and her colleagues followed the participants beginning in the fall of 2004, collecting new data every 12 to 15 months.

Overall, 74 percent of the participants had normal mental function; about 16 percent had MCI; and 10 percent had full-on dementia.

Men were one-and-a-half times more likely to have mild cognitive impairment than women. The prevalence in men increased from 12 percent in men ages 70 to 74 up to 40 percent in the oldest age group, ages 85 to 89. "This was an unexpected finding," Roberts said during a press briefing, referring to the difference between men and women.

The finding remained the same regardless of a man's education or marital status.

"These findings are in contrast to studies which have found more women than men, or an equal proportion, have dementia, and suggest there's a delayed progression to dementia in men," Roberts said. "Alternately, women may develop dementia at a faster rate than men."

Continued study of the participants could help to solve this mind puzzle.

"To be able to find out whether the findings are definitive, we need to follow our subjects over time," Roberts said, "to see if men indeed develop new MCI at a faster rate than women."

The study was supported by grants from the National Institutes of Health and the Robert H. and Clarice Smith and Abigail Van Buren Alzheimer’s Disease Research Program.