PREVALENCE AND INCIDENCE OF DEMENTIA IN THE OLDEST-OLD - A LONGITUDINAL-STUDY OF A POPULATION-BASED SAMPLE OF 84-90-YEAR-OLDS IN SWEDEN

Prevalence and incidence rates of dementia, and the relationship betwe en these rates and mortality, were explored in a longitudinal populati on-based study of individuals aged 84-90 at baseline living in the mun icipality of Jonkoping, Sweden. The subjects were reexamined twice at 2-year intervals using DSM-III-R criteria for dementia. The prevalence rate of dementia at time 1 through 3 was: 31% (N = 97/312), 40% (N = 52/206) and 42%(N = 52/123), respectively, which reflects a 4-years ov erall increase of age in the sample. The 2-year incidence was 19.8% fr om the first to the second wave and 14.9% in the interval between the second and third wave. Of the non-demented at baseline, 22% (N = 48/21 8) had developed dementia within 4 years. A twofold increased mortalit y risk was found in demented subjects. The present investigation confi rms a high prevalence and incidence of dementia in the oldest old. The substantially increased risk of mortality in demented old olds, howev er, counterbalances the high incidence rates, keeping prevalence lower than otherwise would be the case.