P2‐205: Neuropsychological characteristics of clinical dementia rating 0.5 with uncertain impairment

The clinical dementia rating (CDR) is widely used measure of dementia severity and is based on clinical information without reference to neuropsychological test. The global CDR score of 0.5 include three different groups of CDR 0.5/Dementia of Alzheimer Type (DAT), CDR 0.5/incipient DAT, and CDR 0.5/uncertain. Of them, although CDR 0.5/uncertain group is also known to have Alzheimer disease (AD) pathology, they have disagreement in designating CDR 0 or CDR 0.5 between clinicians and their cognitive impairment is unapparent in terms of neuropsychological performance. Therefore, this study aimed to explore the neuropsychological characteristics of CDR 0.5/uncertain. One hundred and five cognitively normal (CN) elderly and 61 individuals of CDR 0.5/uncertain were included in the study. All participants were examined by comprehensive clinical and neuropsychological assessment. Subjective memory complaints (SMC) and geriatric depression scale (GDS) were also administered. CN participants received a CDR score of 0. CDR 0.5/uncertain participants received a CDR score of 0.5. Both group had neuropsychological test z scores above -1.5 according to the age-, education-, and gender-specific norms. There were no group differences in age, education and gender. Level of SMC were significantly higher in CDR 0.5/uncertain than CDR 0 (p = 0.011). Mini-Mental Status Examination (p = 0.049), Rey Complex Figure immediate recall (p = 0.026), and Stroop test (color reading time per item; p = 0.047) were significantly lower in CDR 0.5/uncertain than CDR 0. In contrast, there were no significant differences in other tests assessing attention and psychomotor speed, verbal memory, visuospatial ability, and language. Other clinical features including self-reported depression and family history of dementia or stroke were also not significantly different. Our findings indicate that, although neuropsychological performances are above normative cutoff, clinical assessment of CDR 0.5/uncertain represent significant cognitive changes. These also suggest the possibility that individual with CDR 0.5/uncertain are not only ‘worried-well’ but also exhibit real initial neuropsychological change in addition to AD pathology.