Symptom clusters of subjective cognitive decline amongst cognitively normal older persons and their utilities in predicting objective cognitive performance: structural equation modelling

Background and purpose: Prior literature on subjective cognitive decline (SCD) has mostly focused on memory complaints. It is uncertain whether the other non-memory complaints are equally relevant and can be used, alongside memory complaints, to identify populations at high risk of cognitive impairment. How the memory and non-memory complaints of SCD cluster with each other amongst community-dwelling individuals was investigated, and the differential utility of the symptom clusters of SCD in predicting objective cognitive performance was evaluated.

Methods: This study included 736 participants who were ≥60 years and had normal cognition, using the baseline data of an ongoing cohort study. Participants completed baseline assessments which comprised an SCD scale, a global cognitive measure and neuropsychological tests. Symptom clusters of SCD - as identified from exploratory and confirmatory factor analyses - were included in structural equation models to predict baseline changes in neuropsychological tests.

Results: The symptoms of SCD were split into two distinct factors, of which factor 1 was reported much more frequently than factor 2. Each standard deviation (SD) increment in factor 1 led to a 0.16-0.50 SD increase in global cognition, immediate memory, visuospatial abilities, language, attention and delayed memory (P < 0.05). In contrast, each SD increment in factor 2 worsened some of the cognitive domains by 0.18-0.37 SD.

Conclusions: The various complaints of SCD can have different implications amongst cognitively normal older persons and may possibly be classified into age-related symptoms and pathological symptoms. The findings highlight the need for caution when selecting SCD measures, and illustrate the potential utility of SCD subtypes to inform on the underlying neurobiology.