Retention and longitudinal change in Insight 46, an intensive neuroscience sub-study of the 1946 British birth cohort

Participant retention is a significant challenge in ageing and dementia research. This analysis investigated (a) factors associated with retention in Insight 46, a neuroscience sub-study of the 1946 British birth cohort, and (b) clinical and cognitive changes over 2.5 years of follow-up.

Of 502 participants assessed at baseline (mean[SD] age: 70.5[0.7] years), 442 returned for follow-up (mean[SD] interval: 2.5[0.3] years), representing a retention rate of 88%. Being β-amyloid positive (measures using positron emission tomography), female sex, and older age at baseline associated with lower odds of retention, while completion of neuroimaging and better cognitive performance at baseline- particularly on memory testing- related to higher odds of retention. By the time of follow-up, 14 participants were deceased, 12 of whom were female. Over follow-up, improvements were noted in certain cognitive tests (face-name test, logical memory delayed recall) with declines seen in others (mini-mental state examination, digit-symbol substitution test). Increases in self- and informant-reported cognitive complaints, cognitive disorder diagnoses, and motor abnormalities were also observed, alongside declines in blood pressure. These results have implications for the interpretation and generalisability of Insight 46 data and may be relevant to the planning of other longitudinal studies in this field.