Accidental MCI in healthy subjects: a prospective longitudinal study.

A study was realized on 130 healthy and autonomous volunteers (60-80 years old) who met specific medical and functional inclusion criteria. A comprehensive battery of neuropsychological tests was performed at baseline (M0), 6 and 12 months (M6, M12). At M0 the results indicated that 65% were cognitively normal on each of all the neuropsychological tests, whereas 35% presented a cognitive deficit on one or more tests. At M12, 52% of the subjects who had a cognitive deficit at M0 remained impaired, whereas 48% normalized their scores: they performed as well as the subjects classified normal at M0. The results also indicated that the subjects who remained impaired at M12, had at M0 low scores on three tests or more, whereas the ones who normalized their scores had one or two failed tests. This study focuses on the risk of false positive cases and shows that low scores can be accidental. The authors propose decision rules allowing to reduce the risk of false positive cases. The observation of accidental impairment invites to be cautious and makes this 1-year follow-up study particularly relevant, since a 1-year follow-up is generally needed to diagnose very mild dementia.