Objective: To determine whether selective memory impairment (SMI) on an adapted Mini-Mental State Examination (aMMSE) test increases risk of future dementia in a population-based survey of central Spain.
Background: SMI is a strong predictor of dementia in the elderly. However, most approaches have used extensive memory batteries, which are not always suitable for screening purposes.
Methods: The basal cohort consisted of 2982 poorly educated individuals aged 65 or over. Dementia, stroke and parkinsonism cases were previously excluded. At entry, participants received a structured interview including an aMMSE. Two groups were created according to basal cognitive performance, namely: (1) aMMSE > 23 and no word remembered on the aMMSE delayed-recall task (SMI group); and (2) aMMSE > 23 and at least one word remembered on the delayed-recall task (control group). In a three-year follow-up wave, conversion rate to dementia was calculated and logistic regression was performed.
Results: Of a total of 2507 subjects who completed the two evaluations, 280 qualified for SMI at entry. In the SMI group, 25 subjects (8.9%) developed dementia vs 26 subjects (1.2%) in the control group. Taking the two groups together, and once demographic and medical variables had been controlled, a low delayed-recall score increased dementia conversion rate (OR 0.47, 95% CI 0.34-0.64). Alzheimer's disease was the main cause of dementia (79.8%).
Conclusions: Memory impairment is a risk factor for future dementia in the neurologically-healthy elderly. This can be observed in a subgroup of subjects with SMI defined on the aMMSE delayed-recall subscore. Some other measurements should be added to the SMI construct to improve its predictive validity.
Copyright (c) 2004 John Wiley & Sons, Ltd.