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Jan. 10, 2008 -- The average survival time for people diagnosed with dementia is about four and a half years, new research shows. Those diagnosed before age 70 typically live for a decade or longer.
In an effort to learn more about survival characteristics among patients with Alzheimer's disease or other?dementias, researchers from the U.K.'s University of Cambridge followed 13,000 people who were aged 65 and older for 14 years.
During the follow-up, 438 of the study participants developed dementia and 356 of these people died.
Overall, women lived slightly longer than men after a diagnosis of dementia -- around 4.6 years vs. 4.1 years. And frailer patients died sooner than healthier ones.
But being married, living at home, and even degree of mental decline were not found to have a big impact on survival.
The research is published in the Jan. 11 issue of the journal BMJ Online First.
"When we took everything into account, the big predictors of how long people survive remain sex, age, and functional ability," University of Cambridge professor of epidemiology Carol Brayne tells WebMD. "Functional ability was a much better marker of how close someone was to death than cognitive decline."
Across the globe, dementia rates are expected to double every 20 years for the foreseeable future, with an estimated 81 million cases by 2040.
It is clear from earlier studies that people with dementia have decreased survival compared with people without dementia. Even mild mental impairment linked to dementia is associated with an increase in death risk.
But the characteristics associated with mortality among patients with dementia have not been well understood.
There is general agreement that women with dementia tend to live slightly longer than men, but the impact of other characteristics, including education level, age at diagnosis, and marital status are less well known.
And many previous studies have been restricted to patients being treated for the disorder by a specialist or in a hospital setting, Brayne says.
"We wanted to see what is happening with the entire population, not just people who are treated for dementia," she says.
Slightly over two-thirds of the people in the study who developed dementia were women, and the median age at dementia onset was 84 for women and 83 for men.
The median age at death was 90 for women and 87 for men. And average survival times varied from a high of 10.7 years for the youngest patients (65-69 years) to a low of 3.8 years for the oldest (90 or older at diagnosis).
People with higher education levels had slightly shorter survival times than those with lower education, but the difference was not significant. Living in a nursing home was also associated with slightly shorter survival than living at home, but, again, the difference was not significant.
As in other studies, dementia was associated with shorter survival, but the cognitive level among people with dementia did not appear to play a major role in death.
Researcher Murna Downs, PhD, says most people don't recognize that dementia is a disease people live with, and not just a death sentence.
Downs' research focuses on quality-of-life issues among dementia patients.
"People with dementia live a long time, and we now know that there is a lot of awareness," she says. "People assume that if someone doesn't know where they are they have no other capacity for thinking and feeling. But people with dementia continue to think and to laugh and to feel the rain on their faces, and to try to make sense of their world."
She adds that patients are often isolated because family members or other caregivers fail to recognize their need for interaction and stimulation.
"The therapeutic potential of human contact cannot be underestimated," she says. "You would never put a small child in a chair and let them sit there all day with nothing to do. Children need stimulation and human contact and so do people with dementia."