Subjective cognitive decline (SCD), previously known as subjective memory decline or memory complaint, has been a focus of research for the past 45 years. Our work, along with that of others, has contributed to understanding its role in identifying individuals at higher risk of dementia and its associated risk factors. There has been considerable debate on whether SCD represents an actual risk for dementia or is more of a psychological condition resulting from depression, anxiety, personality factors, education, sex and so on. Whether SCD is caused by these factors or other factors (e.g., genetics) remains to be determined.

A major shortcoming of previous research has been the lack of an assessment measure for SCD with robust psychometric properties (e.g., reliability, validity) using well-established methods (e.g., item response theory, principal component analysis), and examined on a fully phenotyped cohort of participants with access to their neuropsychological, clinical, genetic, imaging, and blood-based biomarkers data. We have developed and published such a measure, namely the McCusker Subjective Cognitive Impairment Inventory (McSCI), which can be reliably used in research projects or with individuals in clinical practice. Here, we will present novel data on the relationship between McSCI self and informant reports with various dementia outcome measures, highlighting the need for such a measure to significantly improve our understanding of the potential causes of SCD and whether it is an indication of “worried well” or actually being “at risk” of dementia.