NORMAL AND PATHOLOGICAL COGNITIVE AGING

The relation of age associated changes of cognitive functions to those of dementia diseases is not well investigated for very old age. Becau se aging as well as dementia diseases are associated with cognitive de ficits, this leads to differential diagnostic problems in very old age . Relevant with respect to this differentiation are on the one hand th e concepts of cognitive ageing, the dementia syndrome and dementia dis eases,and on the other hand empirical findings with respect to 1. the neuropsychological crossectional pattern, 2. the premorbid intelligenc e or adult intelligence level, 3. the speed of decline. ad 1. The spee d of cognitive processes shows a considerable reduction in normal agin g. However, the reduction of learning and orientation as well as prono unced word-finding problems seem to be characteristic of the developme nt of a dementia syndrome. ad 2. The importance of the level of adult intelligence is demonstrated by the possibility that a very old person with low adult intelligence level is diagnosed as demented without su ffering from one of the dementia diseases. In the opposite case of a s lowly progressive dementia disease in a person with a superior level o f adult intelligence a diagnosis of dementia according the standard cr iteria can be given only in an advanced stage of the disease. ad 3. Th e importance of the speed of decline of cognitive performance for the diagnosis of dementia is discussed (e.g. <1 point of the MMSE vs >3 MM SE points per year). An optimization of the time course criterion (cha nge-sensitive tests and an empirically determined cut-off) could impro ve the early dementia diagnosis,which relies up to now mostly on cross ectional features. The more precise assessment of the deterioration sp eed would be an opportunity to investigate the factors or processes wh ich determine the deterioration speed, knowledge of which in turn woul d be a starting point for development of therapy.