Early onset versus late onset in Alzheimer’s disease: What is the reliable cut-off?

Objective: As the literature on conventional criteria for discriminating early-onset (EO) from late-onset (LO) Alzheimer’s disease (AD) is sparse and controversial, the aim of this study was to establish a precise age at onset (AAO) criterion, by using a specific statistical procedure, and to describe the clinical characteristics of the two sub-groups. Methods: Admixture analysis was performed to establish the AAO cut-off in a multi-center study including 2000 AD patients consecutively recruited in eight Italian Memory Clinics. None of the patients were taking acetylcholinesterase inhibitors, antipsychotic or anti-depressant drugs. At the first diagnostic visit, they were administered the Mini Mental State Examination, the Basic and Instrumental Activities of Daily Living and the Neuropsychiatric Inventory to assess clinical phenomenology. Results: Using a specific statistical procedure, we established that AAO that discriminated EOfrom LO-AD was 66. Compared with the LO-AD group, the EO-AD group showed longer duration of illness and a higher educational level as well as less severe functional impairment and delusions. Conclusions: Differences in sociodemographic and clinical characteristics, such as duration of illness, education and delusion severity, suggested the involvement of different pathogenic processes. Additional studies are needed to further investigate the mechanisms underlying the disorder in the two sub-groups of AD patients.