A survey of dementia in the Canberra population: experience with ICD-10 and DSM-III-R criteria.

A community survey of 1045 persons aged 70 years and over was conducted to identify cases of dementia in the cities of Canberra and Queanbeyan. Cases were identified using the Canberra Interview for the Elderly, administered by lay interviewers. When diagnostic criteria were rigidly applied, the point prevalence of dementia in the combined sample of community and institutional residents was considerably lower by ICD-10 than by DSM-III-R. Both criteria showed a similar rise in prevalence with age, and no gender difference. Agreement between the two systems had a kappa of only 0.48. 'Probable' cases by either criteria were identified solely from respondent-provided information in order to include persons for whom no informant was available. The point prevalence of such 'probable' cases was more similar for the two systems, and the kappa coefficient of agreement rose to 0.80. Analysis of the various components required for a diagnosis of dementia showed that the prevalence of all increased with age. Components involving cognitive assessment were correlated with education, but other components were not. The results of the study point to important differences between ICD-10 and DSM-III-R diagnoses of dementia.