The Lothian Birth Cohort 1936 (LBC1936) is a longitudinal study of cognitive ageing. All participants were born in 1936 and had completed the MHT in the Scottish Mental Survey 1947 at a mean age of 11 years14,23. Their recruitment and re-testing in old age has been described previously16. Relatively healthy surviving participants of the Scottish Mental Survey 1947 were identified within Edinburgh and its surrounding area, the Lothians. A total of 1091 participants (548 men and 543 women) were recruited and tested individually at a mean age of 69.5 years (SD = 0.8). The LBC1936 participants completed a large battery of cognitive tests16. For the purposes of the present study, only those tests relevant to the phenotypes analysed here are described. These are: the MHT, and a battery of cognitive tests consisting of 6 tests from the Wechsler Adult Intelligence Scale-III UK (WAIS-IIIUK [Ref. 24]): Digit Symbol Coding, Block Design, Matrix Reasoning, Digit Span Backwards, Symbol Search, and Letter-number Sequencing. Participants also completed the NART22. Following informed consent, venesected whole blood was collected for DNA extraction. Ethical approval for all projects was obtained from Scotland’s Multicentre Research Ethics Committee and the Lothian Research Ethics Committee.
