MONDAY, July 13, 2009 (HealthDay News) -- Scientists tend to think that dementia and Alzheimer's disease taper off in the oldest, but a new study finds that people over 90 have the highest rates.
According to previous epidemiological research, the rate of dementia begins to level off and even decline among people aged 90 and older. But this new study found that the rate of dementia increases with age.
Researchers conducted a population-based study of all people aged 80 or older (2,138 people) in eight municipalities of Varese province in Italy. They were assessed at the start of the study, and the survivors were assessed again an average of three years later.
The study found that dementia prevalence (total number of cases) increased with age: 13.5 percent at 80 to 84 years; 30.8 percent at 85 to 89 years; 39.5 percent at 90 to 94 years; and 52.8 percent among those older than 94.
Prevalence was 25.8 percent among women and 17.1 percent among men.
New cases of dementia also increased with age: 6 percent at 80 to 84 years; 12.4 percent at 85 to 89 years; 13.1 percent from 90 to 94 years; and 20.7 percent among those over 94.
Incidence of new cases was 9.2 percent among women and 7.2 percent among men.
"Gathering reliable information on such a large number of the 'oldest old' makes this one of the largest studies investigating dementia in this age segment of the population," study author Ugo Lucca, head of the Laboratory of Geriatric Neuropsychiatry at the Mario Negri Institute for Pharmacological Research in Milan, said in a news release.
"This study's results confirm that Alzheimer's and dementia are very common among the oldest people in society. We believe this strengthens the need to shift more of the focus of clinical research to this segment of the elderly population," Lucca said.
The study was to be presented Monday at the Alzheimer's Association's annual meeting in Vienna.
Another study presented at the meeting found that the "oldest old" females in Europe have a higher rate of dementia than previously documented. The researchers reviewed data from 26 previously published studies and found that dementia prevalence rates for all men and women up to age 85 confirmed previous findings. However, rates were higher than previously documented among the oldest old females, rising to more than 50 percent among those older than 95.
"Our key findings confirmed that age remains as the single most important risk factor for dementia. Nevertheless, due to the lack of data in the oldest old in previous prevalence studies, the prevalence of dementia of women over the age of 85 had been underreported," study author Dr. Emma Reynish, a geriatrician and coordinator of the European Alzheimer's Disease Consortium from the Victoria Hospital in Kirkcaldy, Scotland, said in a news release.
More information
The American Academy of Family Physicians has more about dementia.
