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Incidence of Clinically Diagnosed Subtypes of Dementia in an Elderly Population

Cambridge Project for Later Life

Published online by Cambridge University Press:  02 January 2018

C. Brayne*
Affiliation:
Department of Community Medicine, University of Cambridge
C. Gill
Affiliation:
Medical Research Council Biostatistics Unit, Cambridge
F. A. Huppert
Affiliation:
Department of Psychiatry, University of Cambridge
C. Barkley
Affiliation:
Department of Psychiatry, University of Cambridge
E. Gehlhaar
Affiliation:
Department of Psychiatry, University of Cambridge
D. M. Girling
Affiliation:
Department of Psychiatry, University of Cambridge
D. W. O'Connor
Affiliation:
Department of Psychogeriatrics, Monash University, Melbourne, Australia
E. S. Paykel
Affiliation:
Department of Psychiatry, University of Cambridge
*
Dr Carol Brayne, Institute of Public Health, Forvie Site, Robinson Way, Cambridge CB2 SR

Abstract

Background

In developed countries, most dementia appears to be due to Alzheimer's disease and vascular dementia. We report rates for incidence of subtypes of dementia based on clinical diagnosis.

Method

This study was a 2.4-year (s.d. 2.6 months) follow-up of a cohort aged 75 years and over, seen initially in a prevalence study of dementia. A screening interview in 1173 survivors was followed in a subsample of 461 respondents by a diagnostic interview 1.8 months after screening (s.d. 1.5 months). This comprised a standardised interview with respondent and informant, with venepuncture where possible. Clinical diagnoses of subtypes were made by specified criteria.

Results

The incidence of Alzheimer's disease of mild and greater severity was 2.7/1000 person-years at risk (1.6–4.4); in men 1.5 (0.8–2.7) and in women 3.3 (1.8–5.9). The incidence of vascular dementia was 1.2/100 person-years at risk (0.7–1.9); in men 1.1 (0.4–2.8) and in women 1.2 (0.7–2.0). Alzheimer's disease, but not vascular dementia, showed a marked increase with age, particularly in women. Rates for minimal dementia of different subtypes showed similar age and sex effects, but were much higher for Alzheimer's disease than vascular dementia.

Conclusions

The striking rise in incidence rates of dementia in the very old appear to be due to Alzheimer's disease, while rates for vascular dementia remain relatively constant. These trends are particularly marked for minimal dementia, but emphasise the importance of Alzheimer's disease in the community as a cause of cognitive decline of all degrees.

Type
Papers
Copyright
Copyright © 1995 The Royal College of Psychiatrists 

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