Alzheimer's disease in its epidemiological context.

The social and public health importance of dementia has been greatly increased by the unprecedented expansion in the world's elderly. By the year 2000, the number of persons in the world aged 65 and over is expected to be about 423 million, nearly 50% of whom will be in developing countries (W.H.O., (1)). Furthermore, it is among the very elderly that the greatest increase is taking place. There will therefore be a marked expansion in the number of persons afflicted by dementia. Because of the profound human and economic consequences of this, there has been a striking increase in research activity in four areas: neurobiological studies, including the molecular biology of Alzheimer's disease (AD); epidemiological research on the dementias and on risk factors for developing it; a search for pharmacological interventions; and research on services for dementia sufferers and their families.