MONDAY, July 28 (HealthDay News) — Rates of dementia in developing countries have been greatly underestimated, according to researchers who used a specially-developed method of calculating dementia prevalence.
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Previous studies have suggested that rates of dementia in developing countries are much lower than in high-income countries. However, the quality and evidence base of these studies are poor, according to the authors of the new study, who are members of the 10/66 Research Group.
The group is named to reflect the global research community's neglect of dementia patients in developing countries. Just 10 percent of research is focused on the 66 percent of dementia patients living in low- and middle-income countries.
The standard DSM-IV criteria for dementia diagnosis are too restrictive, requiring memory impairment (which is not an early feature in some dementia subtypes), and clear evidence of social and occupational impairment (which can be difficult to establish in low- and middle-income countries), according to background information in the study.
The 10/66 group developed its own method of dementia diagnosis, based on an assessment at the person's home, including a clinical interview, cognitive tests, and interviews with family and friends. This approach may reveal more mild and moderate cases of dementia, according to the group.
Using DSM-IV criteria, rates of dementia in developing countries varied widely, from 0.3 percent in rural India to 6.3 percent in Cuba. The prevalence of dementia in urban Latin America sites was 80 percent of that in Europe, in China the prevalence was half of that in Europe, and in India and rural Latin American the prevalence was a quarter or less of that in Europe.
The 10/66 method revealed a higher prevalence of dementia in developing countries and was more consistent across sites, varying between 5.6 percent in rural China and 11.7 percent in the Dominican Republic.
While 847 of the 1,345 cases of dementia identified by the 10/66 method weren't confirmed as DSM-IV dementia, the validity of those 847 cases was supported by high levels of associated disability, the study authors said.
"We believe that our methods have drawn attention to a substantial prevalence of dementia that might have been missed. Prevalence differences between developed and developing countries might not be as large as previously thought," the study authors wrote.
The study was released online by The Lancet to coincide with a presentation at the International Conference on Alzheimer's Disease in Chicago.
— Robert Preidt
SOURCE: The Lancet, news release, July 27, 2008
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