Prevalence of dementia in the 'oldest old' of a Dutch community

To estimate the prevalence rate of dementia in subjects 85 years of age and over.

A two-phase design with the Mini-Mental State Examination (MMSE) in the screening phase and the Geriatric Mental State Schedule (GMS) in the diagnostic phase.

Community survey including subjects in residential care.

All (n = 1,259) inhabitants of Leiden, The Netherlands, aged 85 years and over on December 1, 1986. First phase participation rate was 71% (17% dropout due to death); second phase participation rate was 82%.

DSM-III diagnosis of dementia without further specification of the etiology of the dementia.

An overall prevalence rate of 23% (95% C.I.: 19%-26%) was found. This included 12% mild dementia, 7% moderate and 4% severe dementia. The prevalence rate was higher among women (24%) than among men (18%). It increased with age from 19% (95% C.I.: 16%-22%) in the group of 85-89 years to 32% (95% C.I.: 26%-39%) in the group of 90-94 years to 41% (95% C.I.: 25%-58%) in the 95+ group.

A fifth of the 85+ and a third of the 90+ population suffer from dementia with an indication that half of the 95+ population is affected. With the expected steep rise in the number of the oldest old, dementia will stay a major health problem in the near future.