[Identification errors and delusions of false identification in Alzheimer's disease: a regional survey]

Misidentification syndromes are the main symptoms in Alzheimer's disease. Underlain by complex cognitive, agnosic, and amnesic disturbances of degenerative etiology, they can be expressed by misidentification delusions, as in psychoses. To date, research has focused on identification disturbances of persons selected according to various definitions.

Our main objective was to evaluate the frequency of identification disturbances among patients suffering from Alzheimer's disease within the current conditions of diagnosis and treatment. The secondary objective aimed to establish a detailed analysis of symptoms and clinical correlations, and evaluate the effects of the troubles on the caregiver.

We conducted a regional survey using a questionnaire designed for the caregiver, proposed to the 60 geriatric doctors and neurologists in the Poitou-Charentes region of France, for all patients suffering from Alzheimer's disease (defined according to DSM IV criteria) seen between June 1st and August 31st of 2003. Statview software was used for statistical analysis.

The survey was completed for 104 patients: 69.5 percent women and 30.5 percent men, with a mean age of 79 years. The majority of the patients were seen by a neurologist and presented an average cognitive deficiency (MMS ranging from 11 to 20). An identification disturbance, whether or not it was delusional, all domains included, was found in 81.6 percent of the patients and was related to a more severe cognitive deficiency and greater hardship on the part of the caregiver.

We observed a high prevalence of identification disturbance, which can be explained by the systematic and exhaustive search for identification disturbance. The most frequent disturbance concerned the identification of places, whereas self-identification was less often affected; the authentic Capgras delusion was found less often.

The study of identification disturbances in Alzheimer's disease can contribute to a better understanding of the cognitive, psychopathological, and physiopathological aspects of the disease as well as to a better knowledge and better care for the patient.