This study will compare smartphone usage data between three groups of patients diagnosed with either a memory complaint, mild cognitive decline, or Alzheimer's disease.

Alzheimer's disease (AD) is the leading cause of dementia in the world. The first cognitive function affected is memory and then other cognitive systems are affected leading to a progressive loss of autonomy of the patient. Currently, the diagnosis of AD is made at too late a stage. Patients with memory complaints or mild cognitive decline (MCI) are particularly at risk of developing AD.

However, there is no clinical or paraclinical evidence to predict precisely this risk of progression to AD. Investigator's hypothesis is that there is an association between the evolution of smartphone use and the conversion of cognitive status to AD.

The purpose of this pilot study is to identify existing differences between smartphone use data of patients with a memory complaint or of patients MCI or with an AD. It is a study of 90 patients (30 patients with memory complaint, 30 with MCI and 30 with AD) with a collection of smartphone usage data during three months.

Inclusion Criteria:

• Patient consulting in routine care in one of the CMRR
• No sensory impairment that may compromise smartphone use

Exclusion Criteria:

• Inability to perform MMSE or MMSE < 20 ;
• Other neurodegenerative condition (Parkinson's disease, Lewy body disease, frontotemporal lobar degeneration, amyotrophic lateral sclerosis)
• Severe anxiety or depressive disorder HADS score ≥ 17
• Terminal phase of a severe disease
• Evidence of a lesion on MRI that may be involved in cognitive impairment