Which symptoms can distinguish between subjective cognitive impairment (SCI) and mild cognitive impairment (MCI)?

The SCI, the MCI, and the Alzheimer's disease (AD) are on a spectrum of disease progression; therefore, identification of the earliest signs of cognitive deterioration is becoming a crucial issue. The goal of this study was to examine symptom characteristics and distinguish predictive symptoms in patients with MCI compared with SCI, using caregiver questionnaires. We assessed the Korean Dementia Screening Questionnaire (KDSQ) and Seoul Instrumental activities of Daily Living (S-IADL) of 344 subjects with SCI and 697 with MCI. Multivariate logistic regression analyses were conducted after adjusting for age, sex, and educational status. Common and rare symptoms were similar between the SCI and MCI groups. The most distinguishing features of KDSQ were 'Finds it hard to go somewhere on his/her own using public transportation' (odds ratio=OR=4.56, p<0.0001), 'Has difficulty in operating appliances' (OR=2.47, p=0.001), and 'Keeps repeating the same question' (OR=2.03, p<0.0001). In S-IADL, the most outstanding features were 'using household appliances' (OR=3.99, p<0.0001), 'taking medication' (OR=2.38, p=0.01), and 'using public transportation' (OR=1.94, p=0.04). The dysfunction in 'using household appliance' and 'using public transportation' reflect the possibility of MCI rather than SCI. Therefore, it is suggested that these symptoms also have a discriminative and predictive power in identifying SCI.