Apathy may be a key link between depressive symptoms and subjective cognitive decline

Abstract

AbstractBackgroundSubjective Cognitive Decline (SCD), a potential marker of pre‐clinical AD, is frequently linked to mood disturbances, such as depression and apathy. These associations are thought to hinder the utility of SCD as a predictor of impending disease. However, recent evidence suggests that depression and apathy are separate constructs that may pose differential risk for cognitive impairment and neurodegeneration. Further, some studies have reported apathy to be a more sensitive predictor of cognitive decline than depression. Therefore, understanding the associations between SCD and mood will help refine SCD’s utility as a marker of pre‐clinical AD. This study examines those associations with particular focus on whether apathy mediates the association between depressive symptoms and SCD.Method151 cognitively normal older adults (68% female, mean age 73±7) were assessed for level of SCD, apathy, and depressive symptoms using a 20‐item age‐anchored SCD questionnaire (i.e., “in comparison to others your age”), the Apathy Evaluation Scale and the Geriatric Depression Scale (GDS), respectively. Regression analyses examined the main effects of apathy and depressive symptoms on SCD, and apathy as a mediator between SCD and depressive symptoms. Regression analyses were also conducted after removing three GDS items previously shown to form an apathy factor.ResultApathy (b=.84, p=.001) and depressive symptoms (b=4.57, p=.002) independently predicted SCD. In the mediation model, depressive symptoms predicted apathy (b=2.91, p<.001) but not SCD (b=2.14, p=.183). Apathy mediated the relationship between depressive symptoms and SCD (Indirect effect: b=2.44 SE=.80, CI(1.07, 4.30), accounting for 53% of the total effect. Apathy still remained a significant mediator even after eliminating the apathy‐related items from the GDS (Indirect effect: b=1.52 SE=.65, CI(.40, 2.92)), accounting for 40% of the total effect.ConclusionApathy mediated the relationship between depressive symptoms and memory complaints, even when the GDS only included the dysphoric and anxious elements of depression. These results underscore the relevance of apathy in preclinical stages of disease and is in line with previous studies indicating apathy’s unique association with cognitive impairment and neurodegeneration. Longitudinal studies are required to further disentangle the temporality and potential additive risk for dementia of SCD and apathy.