Grey hair and grey matter: could treating memory disorders prevent dementia?(Editorial Commentaries)

Memory complaints are very common in elderly people. In 1958 Kral (1) had already introduced the terms "benign and malignant senescent forgetfulness," attempting to differentiate between "normal" and pathological decline in memory performance during aging. Since that time the discussion has been continuing and many definitions for a suspected "transitional" stage between normal aging and dementia have been proposed. In the currently widely used criteria of "mild cognitive impairment" (MCI) by Petersen et al, (2) one of the five key elements is objective memory impairment on testing, corrected for age and education, suggesting that age has an influence on memory performance. Yet little is known about the cognitive and structural changes that occur in the normal brain with aging. The study by Lyle et al in this issue tries to define magnetic resonance imaging (MRI) correlates of normal brain aging. (3)

The investigators carried out cranial MRI in 102 very old community dwelling individuals (aged 82 to 94 years). Using a multivariate model with hippocampal size, estimated visually and volumetrically, sociodemographic factors, and age related disease as predictors of memory performance, they found that left hippocampal measurements were predictive, especially on delayed retention of verbal material. Even in a subgroup of cognitively healthy elderly people (clinical dementia rating (CDR) = 0), left hippocampal measures remained predictive of delayed retention of verbal information. For those fond of visual rating of hippocampal atrophy, the results support the view that visual and volumetric estimates of hippocampal size perform equally well. (4)

These results strengthen the already widely known relation between the hippocampus and memory, but what do they tell us about (normal) aging? When comparing the cognitively healthy group (n = 57) with the group as a whole, the difference in influence of age on memory is striking. Age was a significant predictive factor in memory performance in the group as a whole, but lost its predictive value in the cognitively healthy group. In the light of this, is it possible that (a part of) the subgroup of CDR [greater than or equal to]0.5 was mildly demented, and although these subjects were selected from the community, can they still be regarded as representatives of "normal" aging? If not, this might be considered an indication that age predicts memory deficits through the age related presence of hippocampal pathology. In this respect it would have been interesting to compare hippocampal sizes between the two groups. It has been shown repeatedly ...