a1 Department of Psychiatry, University of Bonn, Germany
a2 Institute for Biometrics, Hannover Medical School, Germany
a3 Department of General Practice, University Medical Centre, Düsseldorf, Germany
a4 Department of Primary Medical Care, University Medical Centre, Hamburg-Eppendorf, Germany
a5 Department of Psychiatry, University of Leipzig, Germany
a6 Department of Psychiatry, Technical University, Munich, Germany
a7 Central Institute for Mental Health, Mannheim, Germany
Background The association of subjective memory impairment (SMI) with cognitive performance in healthy elderly subjects is poor because of confounds such as depression. However, SMI is also a predictor for future dementia. Thus, there is a need to identify subtypes of SMI that are particularly related to inferior memory performance and may represent at-risk stages for cognitive decline.
Method A total of 2389 unimpaired subjects were recruited from the German Study on Ageing, Cognition and Dementia in Primary Care Patients (AgeCoDe), as part of the German Competence Network on Dementia. Clusters of SMI according to patterns of response to SMI questions were identified. Gender, age, depressive symptoms, apolipoprotein E (apoE) genotype, delayed recall and verbal fluency were included in a Classification and Regression Tree (CART) analysis to identify discriminators between the clusters.
Results We identified three clusters. Cluster 1 contained subjects without memory complaints. Cluster 2 contained subjects with general memory complaints, but mainly without memory complaints on individual tasks of daily living. Cluster 3 contained subjects with general memory complaints and complaints on individual tasks of daily living. Depressive symptoms, as the first-level discriminator, distinguished between clusters 1 and 2 versus cluster 3. In subjects with only a few depressive symptoms, delayed recall discriminated between cluster 1 versus clusters 2 and 3.
Conclusions In SMI subjects with only a minor number of depressive symptoms, memory complaints are associated with delayed recall. As delayed recall is a sensitive predictor for future cognitive decline, SMI may be the first manifestation of future dementia in elderly subjects without depression.
(Online publication July 11 2007)