Detection of mild dementia in community surveys. Is it possible to increase the accuracy of our diagnostic instruments?
A. Herlitz, B. J. Small, L. Fratiglioni, O. Almkvist, M. Viitanen and L. Backman
Stockholm Gerontology Research Center, Karolinska Institute, Stockholm, Sweden. ahz@psychology.su.se
OBJECTIVE: To investigate the accuracy of cognitive tests and clinical
dementia diagnosis in distinguishing between mildly demented and
nondemented subjects. DESIGN: Three-year longitudinal follow-up of a
community-based cohort sample. Using the Diagnostic and Statistical Manual
of Mental Disorders, Third Edition, Revised as criterion variable, subjects
were classified as demented and nondemented based on the results of
cognitive test performance at time 1. These subjects were then examined
prospectively for development of dementia at time 2. PARTICIPANTS: The
sample consisted of 63 mildly demented (Mini-Mental State Examination score
> 18 < 24) and 398 nondemented subjects at time 1. At follow-up, due
to death and refusal of participation, the sample consisted of 108 demented
and 217 nondemented subjects. RESULTS: The group of subjects who were
considered to be demented according to the results of the cognitive tests
and nondemented by the clinical diagnosis at time 1 had a higher incidence
of dementia at time 2 than did the subjects who were considered to be
nondemented according to both cognitive tests and clinical diagnosis. Among
the incident dementia cases, subjects considered to be demented according
to the cognitive tests but nondemented by the clinical diagnosis performed
at a lower level on most cognitive tests were older, had less education,
and consisted of more women than did the group of subjects who were
considered to be demented by the clinical diagnosis and nondemented by the
cognitive tests at time 1. CONCLUSIONS: A combination of cognitive tests,
especially tasks assessing episodic memory, can detect many subjects in a
preclinical state of dementia who could be missed in the clinical
diagnostic procedure due to subjects' relatively high age, low education,
and female sex. However, cognitive tests also may miss a sizable proportion
of prevalent dementia cases due to possible insensitivity to the same
demographic variables. These findings indicate the need of integration
between clinical and cognitive data to increase the accuracy in detecting
dementia in an early phase.
