Affective Disorders, Mild Cognitive Impairment, and Risk for Dementia

Introduction

Dementia and its most common form, Alzheimer's disease (AD), is a major public health issue.1–3 The experts meeting at the fifth annual Mild Cognitive Impairment (MCI) Symposium agreed that AD should be diagnosed before the onset of dementia, particularly as new interventions are available.4 The concept of MCI is the result of the past 20 years of research efforts to diagnose the prodromes of AD and that of other neurodegenerative dementias. MCI is currently diagnosed using Petersen's criteria: (1) memory complaint, preferably corroborated by an informant; (2) objective memory impairment relative to age- and education-matched healthy individuals; (3) intact general cognitive functioning; (4) absence/few problems with activities of daily living; and no dementia.5 Petersen 6 later suggested the existence of four MCI subtypes: (1) single-domain amnestic MCI (A-MCI; ie, isolated memory impairment), (2) multiple-domain A-MCI (ie, memory impairment and a deficit in at least one other cognitive domain), (3) single-domain nonamnestic MCI (ie, an isolated nonmemory impairment), and (4) multiple-domain nonamnestic MCI (ie, deficits in multiple nonmemory domains). An annual conversion rate to AD or other dementias of up to 20% has been reported,7 as well as a conversion rate of 48% after 30 months of follow-up in individuals with A-MCI.8

Abstract

The concept of mild cognitive impairment (MCI) primarily emphasizes changes in individuals' cognitive functions, but it has recently been suggested that neuropsychiatric symptoms (NPS), and especially affective symptoms, should also be considered important factors in age-related neurodegeneration. This article reviews and summarizes recent evidence, published over the last 3 years, regarding the presence of various affective disorders in healthy older adults and MCI patients, and its relationship to risk for developing dementia. The results presented in this review show that depressive, apathetic, and anxious symptoms can be present in cognitively intact healthy elderly and MCI, and may predict progression to dementia. This article also provides suggestions for future research.

Keywords

depression, apathy, anxiety, MCI, dementia