NEW YORK (Reuters Health) - One in 10 women will reach the age of 85 with their mental abilities completely intact, while another 58 percent will experience only minor reductions in their cognitive abilities, research shows.

According to the study, women who maintain their cognitive function are less likely to have health conditions like diabetes or high blood pressure, less likely to smoke, and more likely to drink moderately, They also have more robust social networks and an easier time with activities of daily living.

Dr. Deborah E. Barnes of the Veterans Affairs Medical Center in San Francisco and colleagues report their findings in the Journal of the American Geriatrics Society.

They note in their report that most research on mental function among older people has compared people with normal mental function to individuals with dementia, but few researchers have looked at how people with very good mental function may differ from those who experience some decline but are still within the normal range.

"There's lots of people who are really sharp until late in life and it's important to try to study that group and figure out what's going on," Barnes told Reuters Health.

To investigate, she and her colleagues analyzed data on 9,704 women participating in a study of osteoporotic fractures. The women were 72, on average, at the beginning of the study, and were followed for 15 years. At the study's outset and four more times during the study, the women were given a test of mental function called the Mini-Mental State Examination.

By the end of the study, 9 percent of the women had not suffered any decline in their cognitive abilities, while 58 percent had minor decline and 33 percent suffered major cognitive decline.

The difference between the women with no decline in mental function and those with moderate decline was small, Barnes noted. These individuals had experienced "very, very mild changes in their memory," she explained. "They were just not quite as sharp, basically."

The women who experienced no cognitive decline were nearly twice as likely to be free of diabetes compared to those who had a minor decline. They were also 20 percent more likely to have normal blood pressure, 70 percent more likely to be non-smokers and 20 percent more likely to be moderate drinkers.

And the women with completely intact mental function were 40 percent more likely to have no problems with activities of daily living, and 20 percent more likely to have strong social networks.

The findings can't prove that these factors are involved in sustaining women's mental function, Barnes noted. Nevertheless, she added, "all the things that we identified have been found to be associated with better health in general, so it makes sense that they would be associated with better brain health."