This multi-centre epidemiological study on healthy ageing in people with intellectual disabilities, with Day Activities as the covering theme, will concentrate on the following subthemes: 1. Mobility and Fitness 2. Nutrition and Nutritional State 3. Mood, Anxiety and Cognition Medical as well as behavioural and care aspects are involved in all themes.Scientific aims of the research project are: 1. to perform for each subtheme baseline assessments of prevalences, risk groups, and secondary health effects, 2. to assess mutual relationships between the themes, 3. to assess specific study questions for each theme, resulting from the consultation of clients, family and staff, 4. to assess acceptation, implementation and health effects of day activity programmes, aimed at healthy ageing. Infrastructural aims are:1. to start a longstanding structural collaboration of the involved university departments and care providers, 2. to support a permanent establishment of the Intellectual Disability Medicine Chair at the Erasmus MC, 3. to increase effective participation of clients and client representatives in healthcare policies and research, 4. to increase specific expertise and a scientific attitude of staff, 5. to advance evidence-based prevention, early detection, diagnosis, treatment and managed care in ageing clients, 6. innovation of day activity care, aimed at healthy ageing, 7. an evidence-base for professional day activities over age 65 years, 8. a registry of (age-related) health aspects, designed for longstanding follow-up.