Methodological issues for population-based research into dementia in developing countries. A position paper from the 10/66 Dementia Research Group

The 10/66 Dementia Research Group has been formed to promote good-quality, internationally comparable research into dementia in developing countries through active research collaboration. In this position paper, we review existing research into dementia prevalence in developing regions of the world. Seven methodologically robust studies were identified. The prevalence of dementia, age-adjusted to the age structure of the Kerala population, ranged from 1.3% to 5.3% for all those aged 60 or over and from 1.7% to 5.2% for all those aged 65 and over. Two studies, from Ibadan, Nigeria and Ballabgarh, India, reported strikingly low prevalence figures. The reported prevalence for most studies was somewhat lower than the consistent figures for Europe reported by the EURODEM concerted action. Based on critical review of the literature, and on the practical research experience of members of the 10/66 group, recommendations have been made for procedure in the following areas: age limits for inclusion in dementia surveys, age ascertainment, sampling, scope for incidence studies, functional assessment and culture- and education-fair dementia diagnosis.