NEW YORK (Reuters Health) - After the age of 90, dementia becomes more and more common among women, while the rate among men appears to stabilize, a study published Wednesday suggests.
The study, of 911 adults age 90 and older, found that 45 percent of women had dementia, versus 28 percent of men. And while the prevalence of dementia among women rose with advancing age -- basically doubling every five years after age 90 -- it remained steady among men.
There are several possible explanations for the sex difference, the researchers report in the journal Neurology.
One is that there may be "sex-specific" risk factors for dementia that become more common among women as they age. It's also possible that the relatively few men who live beyond 90 are hardier "survivors" who have fewer dementia risk factors.
On the other hand, there is some evidence that elderly men and women actually develop dementia at the same rate, lead researcher Dr. Maria Corrada, of the University of California, Irvine, told Reuters Health.
So the reason that more women have dementia at any given age may be that women with the disorder live longer than their male counterparts, she explained. This would be in keeping with the fact that women generally live longer than men do.
It has long been known that the prevalence of dementia among men and women rises markedly between the ages of 65 and 85. But few studies have included adults in their 90s, and when they have, the results have been conflicting -- with some suggesting that the prevalence of dementia levels off after 90, and others showing that it continues to rise.
The new findings now suggest that the patterns differ by sex.
They also show that dementia is a fairly common problem beyond the age of 90, Corrada said.
"As more and more people live to age 90," she noted, "the number of people with this disorder will greatly increase in the next few decades."
Along with the families that will be affected, Corrada said, the healthcare system will have to be prepared to deal with the growing ranks of Americans suffering from dementia.
SOURCE: Neurology, online July 2, 2008.
