Background: There are discrepant findings regarding which subscales of the Cambridge Cognitive Examination (CAMCOG) are able to predict cognitive decline. The study aimed to identify the baseline CAMCOG subscales that can discriminate between patients and predict cognitive decline in Alzheimer's disease (AD) and mild cognitive impairment (MCI).

Methods: This was a five-year case-control study of patients with cognitive impairment and a control group. Participants were grouped into AD (n = 121), MCI converted to dementia (MCI-Ad, n = 43), MCI-stable (MCI-St, n = 66), and controls (CTR, n = 112). Differences in the mean scores obtained by the four groups were examined. Receiver operating characteristic curves were used to compare subscale scores in the AD and MCI-Ad groups with those of controls. The influence of age, gender, schooling, and depression on baseline subscale scores was assessed.

Results: Of the CAMCOG subscales, Orientation and Memory (learning and recent) (OR + MEM) showed the highest discriminant capacity in the baseline analysis of the four groups. This baseline analysis indicated that OR + MEM was the best predictor of conversion to AD in the MCI-Ad group (area under the curve, AUC = 0.81), whereas the predictive capacity of the global MMSE and CAMCOG scores was poor (AUC = 0.59 and 0.53, respectively).

Conclusions: In the baseline analysis, the Orientation and Memory (learning and recent) subscales showed the highest discriminant and predictive capacity as regards both cognitive decline in the AD group and conversion to AD among MCI-Ad patients. This was not affected by age, gender, schooling, or depression.