ABC1921 is one of the three Aberdeen Birth Cohorts whose participants had completed tests of reading and mental ability as schoolchildren in Aberdeen, Scotland. Decades later, these children were recontacted and followed as adults. ABC1921 followed 275 individuals who were born in 1921, completed the Moray House Test as part of the Scottish Mental Survey at age 11 in 1932, and were recontacted between 1997 and 2001 to establish the cohort. The cohort was followed up five times over a 10-year period, from ages 77 to 88 years.