Alzheimer’s disease

Abstract

Introduction and Preliminary ConsiderationsDementia afflicts almost 50 million worldwide (Prince et al., 2015), is the greatest cause of disability in people aged over 65 (Australian Institute of Health and Welfare, 2012), and a leading cause of death in Western countries (Australian Bureau of Statistics, 2016). It substantially impacts family and caregivers, and has a vast economic impact (e.g. > US $950 billion worldwide, Jia et al., 2018). Yet, it is likely to become an even bigger issue, with prevalence anticipated to nearly triple by 2050 (Prince et al., 2015), as survival age increases worldwide. Despite this, dementia remains the only disease within the ten most prevalent causes of death without a reliable method of prevention or cure (Alzheimer's Association, 2017).Alzheimer's disease (AD) is the most common cause of dementia (60-80%; Alzheimer's Association, 2017); and, with the advent of reliable biomarkers, it is clear that AD starts long before dementia is diagnosed. Indeed, AD is now considered a continuum with dementia as the end stage (Jack et al., 2018). Therefore, we will consider the spectrum of AD presentations, from preclinical stages (including subjective cognitive decline, SCD), through the prodromal mild cognitive impairment (MCI) stage, and finally the dementia stage (see Figure 1).

The influence of subjective cognitive decline on prospective memory over 5 years.

“…Once dismissed as “worried well,” subjective cognitive decline (SCD) is becoming an increasingly important area of research within older adult populations, where it is now considered a risk factor for objective cognitive decline and progression to Alzheimer’s disease dementia (Pike & Kinsella, 2019; Rabin et al, 2017). SCD refers to an older adult’s perception of cognitive decline compared with previous functioning, in the context of objective performance within the normative range on neuropsychological assessment (Jessen et al, 2014; Rabin et al, 2017).…”