the respondents for the tilda study were derived from a nationally representative study of the population of ireland aged 50 years and over. 8500 people were interviewed for wave 1 of the study. this involved a computer-assisted personal interview (capi), a health assessment and a self completion questionnaire. the health assessment involved cognitive, gait and cardiovascular tests, as well as procedure to measure macular degeneration. this health assessment was carried out in tilda health centres in dublin and cork. a health assessment will be performed in waves 1, 3 and 5. the capi and the scq will be performed in all waves.