The association between the subjective memory complaints scale and depressive state and cognitive impairment: a factor analysis

Background: We aimed to discriminate individuals with depressive state from individuals with cognitive impairment among community-dwelling people using the subjective memory complaints (SMC) scale. Methods: The study group consisted of 289 volunteers (over 60 years old; 104 males and 185 females). Participants' SMCs were assessed using the SMC scale. The Japanese version of the Center for Epidemiologic Studies for Depression scale and the Mini-Mental State Examination were administered. Participants whose Center for Epidemiologic Studies for Depression scores were 16 or higher were defined as the depressive group and participants whose Mini-Mental State Examination scores were less than 24 were defined as the cognitive impairment group. Exploratory factor analysis was performed to identify the factor structure of the items of the SMC scale. A multiple logistic regression analysis of the association between depressive state and cognitive impairment and the score of each factor was performed. Results: In the final factor analysis model, six items of the SMC scale remained, and a two-factor structure was adequate. Factor 1 included the items 8, 9, and 10 about thought or the ability to think; thus, Factor 1 was defined as "thought disturbance factor". Factor 2 included the items 1, 2, and 4 about memory or forgetfulness; thus, Factor 2 was defined as "memory disturbance factor". In the multiple logistic regression analysis, Factor 1 was significantly associated with depressive state and Factor 2 was significantly associated with cognitive impairment. Conclusion: For individuals with SMCs, we might be able to discriminate depressive state or depression from cognitive impairment or dementia through a detailed investigation using the SMC scale.