Development of robust normative data for the neuropsychological assessment of Greek older adults.

Abstract

Normative data for older adults may be tainted by inadvertent inclusion of undiagnosed individuals at the very early stage of a neurodegenerative process. To avoid this pitfall, we developed norms for a cohort of older adults without MCI/dementia at 3-year follow-up. A randomly selected sample of 1041 community-dwelling individuals (age ≥ 65) received a full neurological and neuropsychological examination on two occasions [mean interval = 3.1 (SD = 0.9) years]. Of these, 492 participants (Group 1; 65-87 years old) were without dementia on both evaluations (CDR=0 and MMSE ≥ 26); their baseline data were used for norms development. Group 2 (n = 202) met the aforementioned criteria only at baseline, but not at follow-up. Multiple linear regressions included demographic predictors for regression-based normative formulae and raw test scores as dependent variables for each test variable separately. Standardized scaled scores and stratified discrete norms were also calculated. Group 2 performed worse than Group 1 on most tests (p-values < .001-.021). Education was associated with all test scores, age with most, and sex effects were consistent with the literature. We provide a model for developing sound normative data for widely used neuropsychological tests among older adults, untainted by potential early, undiagnosed cognitive impairment, reporting regression-based, scaled, and discrete norms for use in clinical settings to identify cognitive decline in older adults. Additionally, our co-norming of a variety of tests may enable intra-individual comparisons for diagnostic purposes. The present work addresses the challenge of developing robust normative data for neuropsychological tests in older adults.