Dementia is thought of as a scourge of the developed world, with its aging population, but it actually may occur at an even higher rate in developing countries, or so, at least, report researchers led by Martin Prince at King's College London U.K., in the May 23 Lancet. A shift in these countries' populations toward aging, combined with low education and undercounting, is blamed for the finding.
The authors are part of the 10/66 Dementia Research Group, which conducts aging studies in 20 low- or middle-income countries in Latin America, Asia, and the Caribbean. The group's name refers to the fact that two-thirds of dementia cases occur in the developing world, but only 10 percent of the research is done there. Previously, the group reported that the prevalence of dementia in elderly people in seven middle-income countries approached Europe's dementia numbers. The new study now adds incidence data from the same populations, reporting higher rates than those seen in Europe. The findings imply that dementia may be an even bigger problem worldwide than researchers have thought. Intriguingly, the authors also find that socioeconomic factors such as a good education and literacy lower dementia risk in middle-income countries just as they do in high-income countries. This supports the idea that cognitive reserve protects the brain in diverse cultures.
In contrast to the new data, several earlier, smaller studies reported lower prevalence and incidence of dementia in less developed countries than in the U.S. and Euope. The 10/66 group contends, however, that the commonly used diagnostic criteria from the Diagnostic and Statistical Manual of Mental Disorders IV (DSM-IV) are too restrictive to recognize all dementia cases, particularly in rural sites.