The aim of this study is to evaluate the efficacy of an anticholinesterase treatment in patients aged 75 and over, hospitalized with delirium.

Study type : Interventional Study design: randomized, double-blind, placebo-controlled study during one month and a 11-month follow-up

Delirium affects up to 50% of hospitalized patients aged 75 and over. Delirium increases risk of comorbid illness, hospital length of stay, institutionalization, and death. Patients with diagnosed or undiagnosed cognitive impairment are at risk to develop delirium. In a prospective study, half of elderly patients with delirium seen in the emergency department had cognitive impairment.

Hypothesis: cholinesterase inhibitors reduce duration and severity of delirium

Main objective:

- to assess the efficacy of cholinesterase inhibitors in patients aged 75 and over hospitalized with delirium

Secondary objectives:

• to describe at one year the percentage of these patients who have a diagnosis of Alzheimer's disease and associated disorders
• to assess the sensitivity to cholinesterase inhibitors in the sub-group of patients with a diagnosis of dementia at one year Design and methods Multicenter, randomized, controlled study with two parallel arms: a rivastigmine group and a placebo group. The study includes a treatment period of one month and a follow-up of 11 months.

Evaluation of the delirium severity will be conducted with DRS-R98 severity each day during the hospitalization.

At day 14, according to DRS-R98 severity score, interruption of treatment or upward dose titration At day 30, last treatment (active or placebo) administration and evaluation with CAM, DRS-R98 severity, MMSE and DSM IV dementia criteria. In case of dementia diagnosis, investigator (MD) will identify the etiologic diagnosis.

At month 3 and 12, evaluation with CAM, DRS-R98 severity, MMSE and DSM IV dementia criteria, number of consultation and hospitalization. In case of dementia diagnosis, , investigator (MD) will identify the etiologic diagnosis.

Inclusion Criteria:

• Patients aged 75 and over
• Hospitalization for delirium not correlated to surgery for less than 48 hours
• Patients with delirium requiring the presence of features 1 (acute onset and fluctuation course), 2 (inattention), 3 (disorganized thinking) and 4 (altered level of consciousness) of the Confusion Assessment Model and DRS R-98 > 10
• Absence of any contraindications to a cholinesterase inhibitor treatment
• Health insurance affiliation
• Having signed an informed consent form
• Caregiver/informant to provide information on patient

Exclusion Criteria:

• Use of IAchE or memantine medication
• Contraindication to IAchE medication
• Frontotemporal dementia
• Diseases involving the short-term survival
• Digestive bleeding
• Ischemic and hemorrhagic stroke related to actual onset (including hemorrhagic contusion)
• Natremia ≤120 mmol/l at the time of hospitalization
• Post epileptic confusion
• Hepato-cellular failure
• Cardiorespiratory impairment at risk of transfer to intensive care unit
• Major sensory deficits that could interfere with cognitive assessment (visual and auditory)
• Not fluent in French
• Being under guardianship
• Absence of caregiver/informant to sign informed consent form