Ascertaining Subjective Cognitive Decline: A Comparison of Approaches and Evidence for Using an Age-Anchored Reference Group

Background Subjective cognitive decline (SCD) is increasingly considered promising to detect preclinical Alzheimer's disease. How SCD is ascertained is critical for determining its potential utility in identifying at-risk individuals, yet SCD measures differ along several dimensions. Objective We aimed to examine the extent to which reports of SCD in healthy elderly may be influenced by the characteristics of the SCD measures. We investigated variations in rates of SCD endorsement across different measures, including an open-ended question. We also examined the association of responses across measures, and the degree to which specific SCD items were associated with objective memory performance. Methods 99 healthy elderly completed a series of questionnaires from which 10 items examining SCD for memory and other aspects of cognition were drawn. We applied Cochran's Q tests to assess differences in rates of SCD, correlation analyses to examine association of SCD responses, and regression models to determine the association between SCD items and delayed verbal memory. Results Rates of SCD varied as a function of the assessment format, ranging from 1 to 7% for memory and 5 to 20% for concentration. SCD was lower for memory versus non-memory domains. SCD items were associated both within and across domains. The most accurate predictor of memory was memory-related SCD in comparison to others the same age. Conclusion Characteristics of SCD items influence rates of endorsement. Querying SCD using an "age-anchored" question may provide the most accurate reflection of actual cognitive performance.