METHODS
Study Design
The Irish Longitudinal Study on Ageing (TILDA) is a large prospective cohort study of the social, economic, and health circumstances of community-dwelling older people in Ire- land. This study is based on the first wave of data, which was collected between October 2009 and July 2011. The sam- pling frame is the Irish Geodirectory, a listing of all residen- tial addresses in the Republic of Ireland. A clustered sample of addresses was chosen, and household residents aged 50 and older and their spouses/partners (of any age) were eligi- ble to participate. Ethical approval was obtained from the Trinity College Dublin research ethics committee, and all participantsprovidedwritteninformed consent. The study design has previously been described in detail.17 Briefly, there were three parts to data collection: a computer-assisted personal interview that included detailed questions on sociodemographic characteristics, wealth, health, lifestyle, social support and participation, use of health and social care, and attitudes toward aging; a self- completion questionnaire; and a health assessment that research nurses performed. Eight thousand one hundred seventy-five individuals aged 50 and older were inter- viewed, of whom 5,037 (61.6%) agreed to attend the health center assessment. Inclusion criteria for the present analysis was a MMSE score of 10 or greater to ensure understanding of the test procedure and valid TUG data, making 4,998 participants eligible for the study.