APOE and early-onset autosomal dominant Alzheimer disease: Methods: This study included 196 older adults from community and memory clinic settings, who underwent assessments for episodic memory, global cognition, and non-memory functions using the Consortium to Establish a Registry for Alzheimer’s Disease (CERAD) neuropsychological battery, with serum selenium levels analyzed via inductively coupled plasma–mass spectrometry (ICP-MS) and APOE genotyping conducted to determine allele status.