Islington study of dementia subtypes in the community

Background Epidemiological studies of dementia subtypes have revealed widely varying distribution rates. There are almost no published community prevalence data for dementia with Lewy bodies (DLB) or the frontal lobe dementias (FLD).

Aims To identify the distribution of dementia subtypes in a representative community population of older people.

Method People aged greater than or equal to 65 years in randomised enumeration districts in Islington, north London, were screened using a reliable and valid questionnaire. People screened as having dementia were assessed in detail and diagnoses were made according to standard diagnostic criteria.

Results Of 1085 people interviewed, 107 (9.86%) met screening criteria for dementia. Diagnoses were made for 72 people (67.3%). Distribution of subtypes varied according to the criteria used; the best-validated criteria yielding: Alzheimer's disease 31.3%; vascular dementia 21.9%; DLB 10.9%; and FLD 7.8% .

Conclusions Alzheimer's disease is confirmed as the most common cause of dementia in older people, followed by vascular dementia. However, DLB and FLD occur sufficiently often to be seen frequently in clinical practice and should be incorporated into future editions of standard diagnostic criteria.