Subjective cognitive complaints are associated with longitudinal changes in episodic memory

Abstract

Older adults with subjective cognitive complaints (SCCs) and no objective impairment may be in a preclinical stage of Alzheimer's disease (AD), based on research linking SCCs to in vivo AD biomarkers, post-mortem AD neuropathology, and elevated incidence of mild cognitive impairment and dementia. Thus, SCCs may reflect a true deterioration in cognitive abilities too subtle to be detected by most standard measures. The present study sought to determine if adults with SCCs showed greater decline in cognitive performance compared to those without SCCs in a large, longitudinal dataset. This retrospective analysis utilized data from the National Alzheimer Coordinating Center on 4,945 normal control participants who received at least one annual follow-up cognitive evaluation. Baseline SCCs were determined by participants’ response to a question about their subjective report of cognitive decline (yes = 3987, no = 958). Annualized mean change was calculated for scores on tests measuring attention, episodic memory, executive function, language, processing speed, and working memory. An ANOVA with Tukey post-hoc comparisons identified differences in mean change as a function of SCCs. An additional analysis explored if the presence of an APOE e4 allele, a genetic risk factor for AD, modulated the relationship between SCCs and longitudinal cognitive performance. The average age at baseline evaluation was 70.2 years and the average follow-up was 4.5 visits. The annualized mean change score differed as a function of SCCs for one test of episodic memory, which involves the immediate, but not delayed, recall of a short story (Logical Memory I, p=0.0047). The group without SCCs demonstrated an annual improvement in immediate recall score [mean(SE)=0.162(0.028)] that was significantly greater than improvement in the group with SCCs [mean(SE)=-0.029(0.061)]. Annualized change scores did not differ as a function of APOE status. Results show that SCCs predict longitudinal performance on a neuropsychological test of immediate recall. Participants without SCCs demonstrated an improvement in scores over repeated administrations, a “practice effect,” which was not observed in the participants with SCCs. Findings suggest that presence/absence of a practice effect may be a sensitive metric for quantifying subtle cognitive changes in individuals with SCCs.