Discovering the determinants of non-pathological cognitive ageing has scientific and practical value: it will be informative about the mechanisms of cognition, and it can suggest interventions to promote successful cognitive ageing [9]. The major determinant of cognitive function in old age is cognitive function in youth [8,10]. It accounts for about 50% of the variance, leaving about half unaccounted for. Therefore, it is valuable first to assess cognition in youth – when cognitive assessment is unaffected by the processes of age and age-related illness – and then re-assess cognition in old age. The Lothian Birth Cohort 1936 is rare in having such data. Among the other determinants of normal cognitive ageing are genetic, medical, psychological, and social and lifestyle factors [3,11-15].
