Cognitive Profiles and Neuropsychiatric Symptoms in Korean Early-Onset Alzheimer's Disease Patients: A CREDOS Study

Background & Objective: Early-onset Alzheimer's disease (EOAD, onset age < 65 years) may differ from late-onset Alzheimer's disease (LOAD) in terms of cognitive profiles and neuropsychiatric symptoms. There have been few studies for Korean EOAD patients using well-structured databases. Previous studies focusing on cognitive profiles between the two groups had a variety of demographic data and comparability. The purpose of this study was to identify the unique profiles of cognitive functions and neuropsychiatric symptoms in Korean EOAD patients that differentiate from LOAD. Methods: Through propensity score matching, a total of 435 patients with EOAD and a total of 435 patients with LOAD were included in this nationwide, multicenter, hospital-based study. Each patient underwent comprehensive neurological examination, interview for caregiver, neuropsychological tests, and brain magnetic resonance imaging. Results: Neuropsychological test results showed worse performances on frontal/executive functions, visuospatial function, and visual memory in EOAD patients as compared to LOAD patients. In terms of neuropsychiatric symptoms, apathy was more common in EOAD patients, while delusions were more prevalent in LOAD patients. The differences in neuropsychiatric symptoms between the two groups were most pronounced in patients with the APOE epsilon 4 allele, suggesting that neuropsychiatric symptoms in AD may be influenced by the APOE genotype. Conclusion: Our results suggested that EOAD may be an important phenotype, fronto-parietal dysfunction, in the spectrum of AD, and this finding can provide for early diagnosis of EOAD patients.