Design & Sample
The input of two groups is critical to the design of the study, people with ID and an international scientific advisory committee. In pursuit of inclusion and participation, people with an ID are included in every stage of the development, design, implementation and dissemination of all waves of the study. Their input helps in the design of pictorial explications to complement all written material increasing the accessibility of the study's questionnaires. An international scientific advisory committee, with extensive experience working with people with intellectual disability, advises on the development of all protocols and provides input on both ID-specific content and advises on the opportunities for comparability with international studies. IDS-TILDA has been granted full ethical approval for all waves of the study by Trinity College Dublin Faculty of Health Sciences Research Ethics Committee.
IDS-TILDA began in 2008 with a sample selected from the National Intellectual Disability Database (NIDD). The NIDD - since replaced by the National Ability Supports System (NASS) - collated information on all people with an ID in the Republic of Ireland eligible for or receiving services. The population included persons at all levels of ID, and the full range of residential circumstances. A nationally representative sample of people aged 40 years and over was drawn from the NIDD and invited to join the study. The original sample recruited at Wave 1 consisted of 753 people with an ID aged 40 years and above. Subsequently, 708 participants took part in Wave 2 and 609 remained in Wave 3. The sample was refreshed in Wave 4, again with support from the Health Research Board, to ensure enough participants for the required analyses. Two hundred and thirty-three new participants were recruited and a total of 739 participants took part in Wave 4. Wave 5 plans to recruit more participants in a purposeful approach, to ensure the sample is representative of the wider population registered on the NASS.