[Viewpoint on the methodology of drug trials affecting cognition of elderly patients].

Clinical trials for cognitive disorders in the elderly require specific methodological guidelines. They must take into account the psychosocial dimension of the patient and his family and must be based on serious neurobiologic knowledge. In degenerative dementias the progress of research concern genetics, molecular intercellular recognition and astrocytic cells. Biology of cognition like hippocampal long term potentiation provides good pharmacologic basis for trials. In normal brain aging several ways must be developed: aminergic systems, free radicals, excitotoxic amino-acid, nerves growth factors. Clinical trials bring informations for pharmacology and epidemiology. Cholinergic neurons are the main pharmacologic target but there are many other ones: GABA-ergic system, Tau protein, amyloid. A rigourous selection of patients allows to precise the nosology of illness responsible of cognitive disorders and to point-out early clinical signs that represent a more sensitive target. Diagnostic criteria are useful in Alzheimer's disease, memory impairment, vascular dementias and other dementias. Evaluation of stage and evolution of dementia, comorbidity, limits of age and caregiver are practical problems. The effects of drugs used to treat cognitive functions are subtle so it is necessary to detect them to choose the best tests in function of each trial. Laboratory investigations can be used to evaluate the response to drug administration. Ethical point of view is represented by the fact that old people with cognitive impairment must not be away from therapeutic progress. In this field we must consider carefully the consequences of cognitive impairment on patient judgment and consent to clinical trial. Legal problems are regulated by supranational rules and French directives of Huriet law.