Alzheimer’s Dementia: An Overview

Alzheimer’s disease (AD), the most common cause of dementia, is a chronic illness characterized by cognitive symptoms, behavioural and psychological symptoms and difficulty in performing activities of daily living. Mild cognitive impairment (MCI) is regarded as a transitional state between healthy cognitive ageing and dementia and around 12–15% of individuals with MCI progress to dementia annually. This provides unique opportunity to initiate treatments targeted to delay or prevent the onset of AD. Based on the age at onset, AD is divided into two broad categories: early onset and late onset. Early onset AD follows the classical mendelian pattern of inheritance, whereas the late onset AD has a complex interplay of gene–environment interaction, with several lifestyle-related risk factors strongly implicated in the pathogenesis of this degenerative condition. The onset of AD pathology predates the clinical symptoms by several years. The neurodegenerative processes in AD is related to the accumulation of abnormally folded Aβ and tau proteins in amyloid plaques and neuronal tangles. Diagnosis of AD is by presence of cluster of clinical features and aided by biomarkers such as CSF Aβ42 and PET amyloid imaging, CSF tau and tau imaging, 18fluorodeoxyglucose uptake on PET and atrophy on structural magnetic resonance imaging increase the diagnostic certainty. In the absence of curative treatments, the management of AD involves pharmacological treatment to delay the onset or progression of AD and supportive care by family members. Targeting these lifestyle-related factors in young adulthood and middle age may be protective against AD. High educational achievement in early life, involvement in cognitively stimulating activity, physical activity and social engagement including rich social network have been associated with reduced risk of late-life dementia and AD.