INCIDENCE OF DEMENTIA IN A POPULATION OLDER THAN 75 YEARS IN THE UNITED-KINGDOM

Background: Incidence studies have been relatively neglected in psychi atric epidemiology. They are particularly important for dementia, sinc e prevalence rates are affected by length of survival, which itself fa lls with increasing age and presence of dementia. Methods: Two-wave co mmunity study of 1195 elderly subjects aged older than 75 years, restu died 2.4 years after a community prevalence study. A two-stage method was used, comprising the Mini-Mental State Examination followed in a s tratified sample by the Cambridge Examination for Mental Disorders of the Elderly (CAMDEX) interview. Incidence rates were based on person-y ears at risk. Results: Annual incidence rates for dementia were 2.3% f or subjects initially aged 75 to 79 years, 4.6% for ages 80 to 84 year s, and 8.5% for ages 85 to 89 years, approximately doubling every 5 ye ars. Rates did not differ significantly by sex, educational level, or social class. Twice as many additional individuals received a diagnosi s of minimal dementia not reaching case threshold. Conclusions: The fi ndings show high rates of new onset dementia, increasing markedly with age, and suggest rapid acceleration of one or more processes that is common in advanced age.