Alzheimer's disease is characterised by a loss of cognitive functions and behavioural problems as set out under the term "Behavioural and psychological symptoms of dementia (BPSD)". The impact of BPSD in everyday life has heavy consequences for the patient and their family. The precocity of incidence, the frequency and the intensity of the BPSD are associated with a rapid decline in cognitive functions, an alteration in the activities of daily living, and a decrease in the quality of life for both the patient and the helper, an increased risk of hospitalisation and of institutionalisation as well as an increase in the cost to the health system. A greater understanding of the risk factors for the occurence of the BPSD would better allow the detection of patients who are particularly at risk for BPSD, to anticipate the crisis situations by proposing early and adapted care, and to better target the medicinal therapies. Certain observational arguments or results of retrospective studies speak in favour of the role of the basic personality in the occurence of BPSD in Alzheimer's disease. The investigators propose to clarify this role through a prospective study.

Inclusion Criteria:

• Male or female subject aged over 50 years ;
• In-patient or out-patient at one of the centres participating in the study ;
• Meeting all the diagnostic criteria for dementia due to AD (NINCDS ADRDA, CDR 1 or 2) or pre-dementia with a CDR of 0.5 (Berr et al., 2006, Dubois et al, 2007) ;
• Covered by the state's Social Security system ;
• With sufficient visual, auditory and oral and written French language skills to complete the clinical and neuropsychological evaluations ;
• Accompanied by a caregiver in sufficient contact with the subject to be able to assess their personality and note the onset of changes in behaviour.

Exclusion Criteria:

• Patients with a progressive and/or poorly managed psychiatric pathology (patients with stabilised depression could be included in the study) ;
• Patients taking any neuroleptic psychotropic medication ;
• Patients taking other psychotropic medication, with the exception of any antidepressant, hypnotic, anxiolytic, acetylcholinesterase inhibitors or Memantine which has been prescribed and stabilised for more than 3 months
• Patients with forms of dementia with an aetiology other than that of Alzheimer's disease (frontotemporal dementia, vascular dementia, Lewy Body dementia, and types of dementia that arise as a result of an underlying untreated disease, such as dysthyroidism, vitamin B12 or folic acid deficiency, syphilis, anaemia or hydroelectrolytic disorders) ;
• Patients with serious, progressive or unstable pathologies which could interfere with the variables under consideration ;
• Deafness or blindness which could compromise evaluation of the patient ;
• Pregnancy ;
• Patients under any type of guardianship or belonging to a restricted category as laid out in the Public Health Code ;
• Patients without a suitable caregiver willing to participate.