Abstract
Background: It is estimated that 590 million people are over 60 and that 18 million of them suffer from dementia; two thirds of whom are living in developing countries. In the Asia-pacific area (which includes few developed countries) it is estimated that 300 million people are over 60 and that this number is likely to double by 2020. There is, however, little information on prevalence rates of dementia and the data available has not been fully explored.
Objective: Exam the English language published population-based studies on prevalence of dementia in China and South-East Asia to assess the regional prevalence of dementia.
Methods: The literature review included a MEDLINE, PSYCHILIT and EMBASE search covering the period between 1980 and 2001. The references from the studies identified and review papers were also examined. The direct standardisation method using the population distribution of one of the studies conducted in Beijing as the standard was used to compare the studies. To assess heterogeneity a logit statistical model was used to further explore the effects of age and the different methodological characteristics of the studies on the prevalences. The methodological variables examined were related to the design, sample and diagnostic assessment used in each study.
Results: Thirteen studies were included in this review. Most of the studies showed that prevalence of dementia increased with age and was higher among women in the older age groups. Alzheimer’s disease was responsible for the majority of cases in those studies which looked at subtypes of dementia. The crude dementia prevalence rates among those 65 years and over varied from 1.8% in Singapore (study5) to 6.7% In Bangkok (study 12). The age standardised prevalences still show a variation between studies, from 1.7% in Taiwan (study 10) to 7.5% in Bangkok (study 12). The prevalence rates were lower than the European rates in the majority of studies. Apart from age distribution, methodological variables related to design, sampling and assessment were found to be a source of the heterogeneity between the studies.
Discussion: The differences in dementia prevalence rates found between these studies and between them and European prevalences might be attributable to regional differences in risk factors for dementia or might reflect the major variations in methodological procedures used in the studies as well the need for more data on prevalence in this area where only four countries were represented. A harmonization of research methodologies needs to be achieved, otherwise any true difference may be concealed by methodological variations. The identification of methodological characteristics that might be affecting the prevalence rates can help to design future prevalence studies.
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