[Prevalence and incidence of dementia among the very old. Review of the literature]

Abstract

Background: The increasing number of elderly and very old people observed in France for more than 20 years raises the problem of an expected increase in the prevalence and incidence of dementia in this population. Prevalence and incidence estimates for persons older than 85 years are incomplete and discordant. This information is crucial for organizing future health and social care.

Objective: Review of literature of prevalence and incidence of dementia for people older than 85 and their link to aging.

Methods: A Medline search has led to a selection of 50 articles.

Results: Some studies conclude that there is an exponential relationship of incidence with age; some, a decrease of dementia in the oldest old population. Prevalence estimates in these studies fluctuate between 15 and 40% and incidence between 60 and 100 person-years.

Conclusion: The variation of prevalence and incidence estimates for 85 and over are partly due to methodological differences and limitations between studies. Further research is needed to include larger samples of persons aged 85 and over and to confirm results where clinical and public health consequences are major issues.