Combining both of the mailings and the media responses, 1226 individuals were interested and eligible for the study. This is, arguably, a good response from a cold mailing to a database that is imperfect and on which only a proportion will have been in education in Scotland in the relevant year. Eighty-five participants withdrew from the study before they were tested, and another 50 had not been contactable or were unable to attend an appointment before the end of testing in May 2007. In total, 1091 individuals became participants in the Lothian Birth Cohort 1936 study and completed the tests and questionnaires, detailed below (Figure 1).
