Background: Cognitive impairment without dementia is commonly observed in ageing populations. The present study aims to describe types of impairment and evolution over a one-year period.
Method: Three hundred and ninety-seven normal French elderly persons demonstrating recent, observable change in cognitive performance were examined annually using a computerised cognitive examination.
Results: Five subtypes were differentiated by cluster analysis. Two of the groups were predicted by logistic regression to be at high risk of senile dementia. Of 16 incident cases of senile dementia diagnosed in the following year, 13 were found to have derived from these two groups. The typology was also found to be useful in the description of age-associated memory impairment.
Conclusions: Subclinical cognitive impairment was found to not constitute a unitary phenomenon and heterogeneous subgroups could be differentiated. The concept of 'normality' in elderly cohorts is reconsidered in the light of these findings.