Plasma amyloid β 42/40 associations on episodic memory: Moderations with depressive symptoms and marital status

Abstract

AbstractBackgroundPlasma amyloid β (aβ) 42/40 is a non‐invasive and cost‐effective biomarker associated with aβ accumulation and cognitive performance in normal aging and Alzheimer’s disease. Recent studies have linked plasma aβ 42/40 to well established modifiable risk factors for dementia. Specifically, depressive symptoms (DS) and marital status have been associated with steeper cognitive decline and increased dementia onset. We examine whether the association between plasma aβ 42/40 and episodic memory (EM) is moderated by (1) DS, (2) marital status, and (3) additive risk of DS+ marital status.MethodWe used an ethnically and clinically diverse longitudinal cohort of older adults (n=473, mean baseline age=74.81(7.22) years, 60.5% women) from University of California, Davis‐Alzheimer’s Disease Research Center (Table 1). Statistical analyses included latent growth modeling to establish a latent EM growth model, and regression analyses to test independent associations and moderations with DS (measured with Geriatric Depression Scale; low<5/ high≥5), marital status (married/not married), and combined DS+marital status risk (low: low DS+married/intermediate: high DS+married or low DS+not married/high: high DS+not married). Age was centered at 75 years. Sex and education were included as covariates.ResultLower aβ42/40 was associated with lower EM performance and steeper decline (level: β=6.195, SE=3.065, p=0.041, slope: β=0.284, SE=0.134, p=0.034). DS and marital status independently moderated this association. Specifically, lower aβ42/40 was associated with (1) poorer EM performance in the high DS groups (n=80; level: β=8.914, SE=4.353, p=0.014) and (2) poorer EM performance and steeper decline in the married group (n=115; level: β=11.157, SE=4.477, p=0.013, slope: β=0.524, SE=0.219, p=0.017). The effects of these independent associations were magnified with combined DS + marital status. Specifically, lower aβ42/40 was associated with poorer EM performance and steeper decline in the low (n=62; level: β=15.445, SE=5.650, p=0.006, slope: β=0.642, SE=0.305, p=0.035) risk group but this association was absent in the intermediate (n=171) and high (n=56) groups.ConclusionThe impact of amyloidosis, as measured by plasma aβ42/40 on cognition, may be more prominent in married older adults with low DS. Examining multimodal associations of non‐invasive plasma biomarkers with modifiable risk factors may identify older adults with high cognitive decline and dementia risk profiles.