title: Design and methodology of the Irish Longitudinal Study on Ageing.
abstract: OBJECTIVE
  To provide comprehensive data on older people in Ireland and new insights into the causal processes underlying the aging transformation.
  
  
  METHODS
  The Irish Longitudinal Study on Ageing (TILDA) is a population-representative prospective cohort study with baseline assessment conducted between October 2009 and February 2011 and follow-up waves planned every 2 years. Participants were sampled in geographic clusters, with each member of the Irish population aged 50 and older having an equal probability of being invited to participate in the study.
  
  
  METHODS
  Community-living population of the Republic of Ireland aged 50 and older.
  
  
  METHODS
  Eight thousand one hundred seventy-five participants aged 50 and older at time of interview participated in the study, along with 329 spouses or partners younger than 50.
  
  
  METHODS
  The Irish Longitudinal Study on Ageing includes detailed assessments of the mental and physical health and social and financial circumstances of participants, which are assessed in a home interview, a self-completion questionnaire, and a detailed health assessment that takes place at a dedicated health center or in the respondent's home.
  
  
  RESULTS
  The response rate was 62.0%, with response rate varying according to educational attainment. Data from the first wave of data collection are available for researchers at the Irish Social Sciences Data Archive.
  
  
  CONCLUSIONS
  The Irish Longitudinal Study on Ageing provides an opportunity to study the interactions between the health and social and economic circumstances of the older population in a nationally representative sample.
authors.affiliation: Department of Medical Gerontology, Trinity College Dublin, Dublin, Ireland.
authors.forename: Brendan J
authors.initials: BJ
authors.lastname: Whelan
authors.forename: George M
authors.initials: GM
authors.lastname: Savva
mesh_terms: D000368:Aged; D000375:Aging / Q000208:ethnology / Q000523:psychology; D004522:Educational Status; D015340:Epidemiologic Research Design; D005260:Female; D015577:Geriatric Assessment; D054624:Health Status Disparities; D006306:Health Surveys; D006801:Humans; D007494:Ireland / Q000453:epidemiology; D008137:Longitudinal Studies; D008297:Male; D008603:Mental Health; D008875:Middle Aged; D012179:Retirement / Q000523:psychology / Q000706:statistics & numerical data; D012944:Social Support; D012959:Socioeconomic Factors; D011795:Surveys and Questionnaires