P73. A new cognitive diagnostic marker to distinguish between Subjective Cognitive Decline, mild cognitive impairment and healthy adults?

Patients with Subjective Cognitive Decline (SCD) have an increased risk of Alzheimer’s diseases (AD) pathology while their performance in usual cognitive tests is normal. The goal of the present study was to assess whether another cognitive test, late verbal recall, can distinguish between SCD, mild cognitive impairment (MCI) and no cognitive impairment (healthy controls, HC). We used a late recall method which has so far only been applied in epilepsy patients ( Witt et al., 2012 ). After being screened with the CERAD test battery ( Morris et al., 1989 , Mirra et al., 1991 ) patients from our memory clinic were called 24 h later and asked whether they still remembered words of the list they had to learn the day before. We also carried out the sleep quality (PSQI) and the smell function (Sniffin Sticks test) and compared the performance in SCD to a healthy control group and patients with mild cognitive impairment. Smell values and word recall differentiated between MCI and HC/SCD. HC and SCD did not show a significant difference in smell functions and late word recall. Sleep quality only differed between HC and MCI. Smell and late recall performance were correlated with each other and can predict the MMST score. Sleep quality did not explain additional variance in a regression model. Raw values of late recall showed highest sensitivity and specificity compared to sleep and smell. These findings reveal that the smell test and the late recall test were able to distinguish between SCD and MCI, but not between SCD and healthy controls. The regression model proves that our late recall method is a better predictor for cognitive impairment in MCI and SCD than smell or sleep. Our next goal is to define a marker that distinguishes between SCD patients who stay healthy and those who will develop objective cognitive decline. The question will be whether individual differences in SCDs performance (late recall, smell, sleep) can predict the probability for developing AD.