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The gap between prevalence of dementia in developing and higher-incomecountries may be much smaller than previously estimated, according to astudy released on July 28, 2008 in The Lancet.
Previously, studies have indicated that dementia is less prevalent indeveloping countries than in high income countries, a difference thathas been attributed to a relatively aged population in the latter.However, according to the background information in the article, theseprevious studies lack quality and need a wider evidence base,particularly in studies from Latin America, Africa, the Middle East,eastern Europe and Russia.
In 1998, the 10/66 Dementia Research Group was established as a part ofthe Alzheimer’s Disease International, based in King’s College London,in order to draw attention to the disparity in research of dementia indeveloping and high-income countries. At the time, while 66% ofpatients with dementia were living in low and middle income countries(LMIC), only 10% of research focused on this population.
In 1999, the group developed and validated diagnostic methods of thisdisease in a large-scape pilot study in 25 LMICs. Their diagnosis isbased on a 2-3 hour assessment in the home of the subject, including aclinical interview, cognitive tests, and informant interviews.Balancing these results then leads to a diagnosis. These are generallyless restrictive than the standard Diagnostic and Statistical Manual ofMental Disorders (DSM-I) criteria, which include: memory impairment,which is not an early feature of certain dementia subtypes; and clearevidence of social and occupational impairment, which can be difficultto establish in LMIC settings. As a result, the 10/66 diagnosticcriteria may reveal more subtle cases.
To learn more about dementia in developing populations, Professor JuanLlibre Rodriguez, Medical University of Havana, Cuba, and ProfessorMartin Prince, Institute of Psychiatry at King’s College London, UK,and colleagues from the 10/66 Dementia Research Group evaluated 14,960subjects in China, India, Cuba, Dominican Republic, Venezuela, Mexico,and Peru aged 65 years and older. Both the 10/66 and DMV-I criteriawere used and the latter was compared to previously published studiesin European countries.
According to the DSM-IV criteria, the prevalence of dementia variedwidely, as low as 0.3% in rural India and as high as 6.3% in Cuba. Whenadjusted for age and sex, in comparison to European estimates, theDSM-IV prevalence was 80% of this in urban Latin American sites, 50% ofthis in China, and less than 25% of this in India and rural LatinAmerica. The prevalence of dementia according to the 10/66 guidelineswas generally higher and more consistent across the populations, withprevalence as low as 5.6% in rural China and as high as 11.7% in theDominican Republic. OF the 1,345 cases of 10/66 dementia, 847 were notconfirmed by DSM-IV criteria, the authors supported this with evidenceof high levels of associated disability.?
The authors close with warning about the underestimates of dementia inLMIC countries: “Our conclusion is that the DSM-IV dementia criterionmight substantially underestimate the true prevalence of dementia,especially in least developed regions, because of difficulties indefining and ascertaining decline in intellectual function and itsconsequences. We believe that our methods have drawn attention to asubstantial prevalence of dementia that might have been missed.Prevalence differences between developed and developing countries mightnot be as large as previously thought.”
Dr Eric Larson, Group Health Center for Health Studies, Seattle, WA,USA and Dr Kenneth Langa, University of Michigan, Ann Arbor, MI, USA,contributed an accompanying comment in which they support the 10/66criteria in this analysis. “The 10/66 study will provide uniqueopportunities to explore environmental effects on the ageing process inthe brain…we applaud the 10/66 authors’ focus on actual function andespecially functional impairment, which leads to suffering anddependency. We should work towards letting more of the world’s peopleexperience long life as a reward for their many years of life on earth- not as punishment for the triumphs of modern medicine and publichealth.” They say.
This study will be presented at the International Conference onAlzheimer’s Disease (ICAD) the weekend of July 26. These results willbe expanded over the next few years, as the 10/66 group collects moredata from their network of 15 sites in 11 different countries.
Prevalence of dementia in Latin America, India, and China: apopulation-based cross-sectional survey
Juan J Llibre Rodriguez, Cleusa P Ferri, Daisy Acosta, Mariella Guerra,Yueqin Huang, K S Jacob, E S Krishnamoorthy, Aquiles Salas, Ana LuisaSosa, Isaac Acosta, Michael E Dewey, Ciro Gaona, A T Jotheeswaran,Shuran Li, Diana Rodriguez, Guillermina Rodriguez, P Senthil Kumar,Adolfo Valhuerdi, Martin Prince, for the 10/66 Dementia Research Group?
Published Online The Lancet July 28, 2008
DOI:10.1016/S0140-6736(08)61002-8
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The rising tide of dementia worldwide
Published Online The Lancet July 28, 2008
DOI:10.1016/S0140-6736(08)61003-X
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Written by Anna Sophia McKenney
Copyright: Medical News Today