Dementia raises death risk in oldest elderly

By Amy Norton

NEW YORK (Reuters Health) - Alzheimer's disease and other forms of dementia may have a particularly strong impact on life expectancy among the oldest elderly.

In a study published in the journal Neurology, researchers found that 95-year-olds with dementia were less likely to survive to their 100th birthday than those without dementia.

While dementia is known to shorten life expectancy, few studies have included people older than 90. The new findings suggest that Alzheimer's and similar conditions may have an even greater impact on mortality among these oldest elderly.

"We found that the effect was even more significant compared with younger elderly," lead researcher Dr. Anne Borjesson-Hanson told Reuters Health. "Forty percent of the deaths after age 95 were explained by dementia, which could be compared with 17 percent explained by cardiac diseases and 6 percent by cancer."

The study, which followed 338, 95-year-old adults, is the largest to date of nonagenarians with dementia, noted Borjesson-Hanson, of Goteborg University in Sweden.

At the beginning of the study, all participants were assessed for dementia and signs of less-severe declines in mental functioning. A total of 174 had Alzheimer's disease or another form of dementia.

Five years later, 15 percent of participants were still alive, with the rate of death being higher among those with dementia at the outset. Only 4 percent of 95-year-olds with dementia survived to age 100 versus 27 percent of those who were initially dementia-free.

It's not entirely clear why so few dementia patients survived over the study period, the researchers admit. Dementia "could be seen as part of a terminal decline," Borjesson-Hanson explained, and indicate a general deterioration in bodily functions.

If, on the other hand, the higher death rate stems from some shortcoming in care, she said, that will need to be addressed.

SOURCE: Neurology, November 27, 2007.