Guidance describing all the cognitive tests across all the cohort studies. This will include availability of the measures across studies and sweeps, what they intended to measure, reliability and validity measures, how to construct (including syntax) and interpret the measures, along with appropriate references and illustrations of previous work applying the variables. We will also provide a set of derived cognitive measures, with syntax and documentation, including harmonized measured for cross-cohort analysis. This will make the data more accessible to new groups of users, and facilitate cross-cohort analysis. As well as providing guidance for analysts on these measures, this exercise will be valuable for future cohorts, by identifying which cognitive measures are likely to add most value to future datasets, and which add little value. We will disseminate our findings and guidance via: academic journal articles; CLS webinars; and press releases and writing for a general audience, as appropriate. We anticipate that our substantive findings regarding cognition and socio-economic differentials will have wider impact.