Between June 2004 and November 2006, 3686 invitations were sent out in this way. This is lower than the original number of 1936-born individuals identified on the CHI because changes in circumstances of those listed can occur over a period of time. Of the 3686 individuals invited to participate, 1703 responded (46.2% of those contacted) (Figure 1). Two hundred and eighty six – or 16.8% of the respondents – were not interested in hearing more about the study. From the details included on the reply slip it was possible to determine that 209 of these refusals were from otherwise eligible individuals, 46 were ineligible, 9 were refusing for some medical reason, and 22 did not provide the details required to ascertain their eligibility. Sixty-six respondents did not indicate whether they were interested or not. However, 5 detailed medical conditions which would not allow them to participate, 2 were born in years other than 1936, and the remaining 59 were ineligible due to their country of schooling. 'Interested' responses were received from 1351 individuals (79.3% of the responses), although 83 of
