A battery of 21 cognitive performance tests is administered each year (Table 1) [43–55]. The Mini-Mental State Examination (MMSE) [43] is primarily used to describe the cohort. Eleven tests are used for diagnostic classification. Nineteen tests that assess a range of cognitive abilities are used to construct separate summary measures of global cognitive function and five cognitive domains, including episodic memory, semantic memory, working memory, perceptual speed, and visuospatial ability. The composite measures are created by converting each test within each domain to a z-score and averaging the z-scores, as previously described [56]. Seven tests can be administered by telephone. The telephone version yields composites for episodic memory, semantic memory, and working memory, in addition to global cognition.
