The Amstel project: design and first findings. The course of mild cognitive impairment of the aged; a longitudinal 4-year study.

The AMSTEL-project is a longitudinal investigation to study the course of cognitive impairment in people aged 65 and over during a 4-year period. The study intends to contribute to the distinction between normal aging and early dementia, and should ultimately result in a diagnostic instrument enabling general practitioners to distinguish early dementia, in particular Alzheimer's disease, from normal aging. Another goal of the project is to elucidate the contribution of advanced biomedical methods (SPECT, MRI) to the early diagnosis of the main types (SDAT, MID) of dementia. This paper describes the design of the study, especially the recruitment of the study population and the sampling procedures. The investigation started in March 1990, and the first findings are presented. The procedure to approach the population resulted in a refusal rate of 45% for the screening phase. The reasons for this high non-response rate are discussed.