Prevalence of dementia according to DSM–III–R and ICD–10

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Abstract
Background: The prevalence of dementia diagnosis according to ICD–10 and DSM–III–R in population surveys remains poorly understood.Aims: To report and compare prevalence rates according to DSM–III–R and ICD–10.Method: A population-based sample (n=1692, age 75+ years) was investigated by a Structured Interview for Diagnosis of Dementia of Alzheimer Type, Multiinfarct Dementia and Dementia of other Aetiology according to DSM–III–R and ICD–10 (SIDAM).Results: Whereas 17.4% (95% CI=15.9–19.5) of individuals aged 75+ years suffer from dementia according to DSM–III–R, only 12.4% (95% CI=10.6–14.2) are diagnosed as having dementia according to ICD–10. The results revealed lower ICD–10 rates in all investigated age groups. The largest differences appear in the oldest of the elderly.Conclusions: The ICD–10 sets a higher threshold for dementia diagnosis. Larger differences in the eldest age groups might reflect difficulties in applying case definitions, especially in those beyond 90 years old.