[What is dementia? 2. A fuzzy construct].

Abstract

Since the publication of the third edition of the classification of mental disorders by the American Psychiatric Association, APA (DSM-III) in 1980, a large international consensus has been reached to define dementia as a multiple cognitive deficit centered by memory disturbances, interfering with the daily life activities and related to organic brain lesions. The DSM-III defined a diagnostic strategy in two steps. First to make the diagnosis of dementia according to the clinical criteria and then to specify its etiology. The more recent editions of the APA classification did not significantly modify these recommendations. The use of the DSM criteria has allowed important advances in epidemiological, clinical and therapeutic research. However, several criticisms should be addressed to the clinical diagnostic criteria as well as to the current concept of dementia. First, from a theoretical point of view, dementia is not a disease, not even a disorder. It only corresponds to a conventional collection of symptoms. Actually, clinical symptoms of dementia basically depend of the localization of brain lesions. Therefore, there could not be one single dementia syndrome. Similarly, the basis of the search for one "antidementia drug" should be questioned. From a clinical point of view, the DSM-IV criteria present some inaccuracies regarding the description of deficits in memory and executive functions as well as in the assessment of the interference of the cognitive decline with the activities of daily living. The definition of dementia as a purely cognitive deficit results in neglecting its psychological and relational manifestations which play a large part in the detection of dementia and its acceptance by the family. A major criticism concerns the definition of dementia as a sincle clinical entity with memory deficits as the core symptom. This definition is well adapted to Alzheimer's disease but results in delayed diagnosis or misclassification of dementias such as frontotemporal dementia or dementia with Lewy bodies in which memory deficits are minor or late. Presently, diagnostic strategy should be directed towards specific entities such as Alzheimer's disease which can be diagnosed accurately in mildly impaired individuals. It is proposed that the term dementia should only be used to specify a degree of severity of the disease, corresponding to the restriction of the patient's autonomy.