Global cost of hospitalization will be retrieved from the local PMSI (Medicalization program of the information system) databases after study completion

Vital status (alive or deceased) will be collected at T3, T6, T9 and T12, from the foster caregiver.

Occurrence of lower respiratory tract infections will be collected using the RUD-lite. For the diagnosis of lower respiratory tract infections, at least two of the following must be present and a doctor must confirm the clinical evidence: Cough (starting or worsening) that may produce phlegm, specific clinical signs during auscultation; Fever. (≥38°C); Chest pain ; Rapid, shallow breathing ((≥25 per minute) ; Confusion or increased dependency.

The foster caregiver will complete this question at inclusion and at subsequent follow-ups (T3, T6, T9 and T12).

Total number of falls since the last visit will be collected at T6 and T12 from the foster caregivers.

The level of cognitive deterioration of the participants will be with the Mini Mental State Examination (MMSE). This 30-item scale assesses the severity of cognitive deterioration through items of orientation, learning, attention and arithmetic, memory, language, and constructive praxis.

The scale is rated from 0 to 30, reflecting the level of cognitive impairment. The participant will complete this questionnaire at inclusion, T6 and T12.

Depressive symptoms will be assessed using the CES-D (Center for Epidemiologic Studies- Depression Scale validated in French by Fuhrer & Rouillon This 20-item questionnaire assesses depressive symptomatology, including 4 items on positive affect (happiness, self-worth, confidence, enjoyment). Frequency of symptom occurrence during the past week is assessed by the participant using a 4-point Likert scale ("never", "occasionally", "quite often" and "frequently"). The score ranges from 0 to 60. The higher the score, the more significant the symptomatology. Data will be collected at inclusion, T6 and T12. For statistical analyses, the variable will be dichotomized (1 = presence of depression and 0 = absence of depression). The participant will complete this questionnaire at inclusion, T6 and T12.

Feeling of loneliness will be captured with the 14th item of the CES-D (14, 15): " I felt lonely ". The participant will complete this test at inclusion, T6 and T12

Total number of medications taken by participants will be collected from the foster caregiver at inclusion, T6 and T12 to assess polypharmacy.

Malnutrition will be assessed with the short version of the Mini Nutritional Assessment (18). This questionnaire assesses nutritional status. A score under 12 indicates probable undernutrition. For the analyses, the variable will be dichotomized accordingly (1 = undernutrition; 0 = no undernutrition). The participant will complete this questionnaire at inclusion, T6 and T12.

The Short Physical Performance Battery (SPPB) will help to identify sarcopenia. Three subtests measure lower-extremity functions: keeping balance (feet side-by-side, semi-tandem, tandem balance position, to be kept for 10 seconds each), walking 4 meters at usual pace, yielding a gait speed ratio (meter per second) ; standing up and sitting down five times as quickly as possible with the arms folded. Each movement is scored 0-4 points out of a total score from 0 to 12, with higher scores showing better physical performance. If total score is under 8, there is a risk of sarcopenia. For the analyses, the variable will be dichotomized accordingly (1 = sarcopenia; 0 = no sarcopenia). The participant will complete this test at inclusion, T6 and T12.

Frailty will be assessed at inclusion, T6 and T12 using Fried's phenotype (weight loss, exhaustion, low physical activity, slowness, weakness) and will be analyzed as a dichotomous variable, i.e. 1 = Fragile and 0 = Not Fragile. Information on the different components of the phenotype will be retrieved from the MNA, the SPPB and a hand-grip strength test using a dynamometer, at inclusion, T6 and T12.

Sensory impairments (audition and vision) will be addressed by directly asking the professional caregiver. Variables will be dichotomized accordingly ((1 = hearing / vision impairment; 0 = hearing / vision impairment). The foster caregiver will complete this questionnaire at inclusion, T6 and T12.

The level of independence in Activities of Daily Living (ADL) and incontinence will be assessed using the Katz's scale, a 6-item scale assessing independence in 6 basic activities of daily living: bathing, toileting, eating, dressing, incontinence. For each activity, a score of 1 indicates complete autonomy, a score of 0.5 indicates partial autonomy, and a score of 0 indicates complete dependency. The foster caregiver will complete this questionnaire about the participant at inclusion, T6 and T12.

The level of independence in Instrumental Activities of Daily Living (IADL) will be assessed using Lawton's IADL scale. The foster caregiver will complete this questionnaire about the participant at inclusion, T6 and T12.

In France, the AGGIR questionnaire has been developed by public authorities to quickly assess the degree of dependency of elderly people, and assign a dependency group, ranging from 0 (bedridden, completely dependent) to 6 (no help required, the person is autonomous in everyday activities.) This scale is routinely completed by every nursing home at admission and updated when necessary to reassess healthcare pathways. The foster caregiver will complete this questionnaire about the participant at inclusion, T6 and T12.

Psychological and Behavioral Symptoms in Dementia will be assessed with the short version of the NeuroPsychiatric Inventory or NPI. This scale assesses presence, severity for the patient and impact on the professional's workload of an array of psychological and behavioral manifestations (agitation, hallucinations, apathy, etc.) as well as neurovegetative symptoms (sleep and appetite). The foster caregiver will complete this questionnaire about the participant at inclusion, T6 and T12.

Risk of developing pressure ulcers will be assessed with the Braden's Scale, and pressure ulcers will be classified according to the National Pressure Ulcer Advisory Panel, European Pressure Ulcer Advisory Panel and Pan Pacific Pressure Injury Alliance. The foster caregiver will complete this questionnaire about the participant at inclusion, T6 and T12.

Quality of life of the participant will be assessed using the QoL-AD (Questionnaire Quality of Life - Alzheimer's Disease). This 13-item questionnaire assesses the participant's physical condition, mood, relationships with friends and family, financial difficulties, and overall quality of life. The self-rated and the proxy-rated version of the questionnaire will be administered to the participant and the caregiver, respectively. The items are evaluated using a 4-point ordinal scale ranging from poor to excellent, with a total score ranging from 13 to 52. For the weighted score, the participant's score is multiplied by 2, the caregiver's score (about the participant's quality of life) is added, and the total is divided by 3 to bring the score back to the initial scale. The participant and the foster caregiver will complete this test at inclusion, T6 and T12.

Health-related quality of life of the participant will be assessed with the EQ-5D questionnaire. This questionnaire assesses health conditions. It is the most widely used questionnaire in medico-economic analyses. It allows health outcomes to be assessed in terms of QALYs (Quality-Adjusted Life-Years). This indicator summarizes the length and quality of life in a single figure. The result of a cost-utility analysis is expressed in terms of the cost of gaining one QALY (i.e. one year lived in perfect health). To estimate QALY, health-related quality of life is designed on a continuum from 0 (death) to 1 (perfect health). Each health status is thus assigned a weight of 0 to 1, the higher the corresponding quality of life.

The participant and the foster caregiver will complete this test at inclusion, T6 and T12

Adaptation to the foster family will be assessed at inclusion, T6 and T12 using Castonguay & Ferron's scale. This is a 17-item scale designed to identify people who have difficulties to adjust to nursing home life, and that we adapted by replacing "nursing home" by "foster home". The participants must answer "yes" or "no" to a series of statements about their daily life and habits in the residence. A score of 16 or 17 indicates a good general adaptation, while a score of 11 or less indicates significant difficulties. The participant and the foster caregiver will complete this test at inclusion, T6 and T12

Foster caregivers' quality of life will be assessed with the Medical Outcomes Study Short-Form General Health Survey - 36 items (SF-36, a widely validated health-related quality of life questionnaire, that uses questions on physical, social and psychological domains. The foster caregiver will complete this questionnaire at inclusion and at T6 and T12.

Symptoms of burnout will be assessed with the Pro-QoL scale (professional quality of life scale). This 30-item questionnaire yields three domain-specific scores: burnout risk, compassion, and compassion fatigue. The foster caregiver will complete this questionnaire at inclusion, T6 and T12.