Regression-Based Cognitive Change Norms Applied in Biochemically Defined Predementia Alzheimer’s Disease

Abstract

Objective: We aim to develop 2-year cognitive change norms for adults ages 41–84 for six cognitive tests, and to evaluate these norms in groups with AD biomarkers. Background: Practice effects are common in repeated neuropsychological testing. Not accounting for practice effects may obscure cognitive decline in early Alzheimer’s disease (AD). Method: We developed standardized regression-based change norms from normative samples consisting of healthy controls from the Dementia Disease Initiation study (n = 125), the Trønderbrain study (n = 57), and the Gothenburg mild cognitive impairment (MCI) study (n = 65). Norms were applied in a sample with cognitive symptoms (subjective cognitive decline or MCI) and AD cerebrospinal fluid (CSF) biomarkers (n = 246), classified according to the A/T/N system. Results: The change norms adjusted for pertinent demographics and practice effects. The group with cognitive complaints displayed a trend toward cognitive decline compared to the normative group, with the A+T/N+ subgroup showing the most marked decline. This was observed in tests of episodic memory and cognitive flexibility/divided attention. Conclusions: We present 2-year cognitive change norms for adults between 41 and 84 years, adjusted for practice and demographics. A web-based change norm calculator is provided.