What is dementia?

What is Dementia

Dementia is a chronic, acquired syndrome characterized by significant impairment in two or more cognitive domains—such as memory, reasoning, language, visuospatial abilities, or behavior—that represents a decline from previous functioning and interferes with the ability to perform work or usual daily activities. 1

Core Defining Features

Dementia must meet all of the following criteria to be diagnosed 1:

• Cognitive or behavioral symptoms that interfere with ability to function at work or in usual activities 1
• Represents a decline from previous levels of functioning and performance 1
• Not explained by delirium or major psychiatric disorder 1
• Detected through combination of history-taking from patient and knowledgeable informant plus objective cognitive assessment 1

Affected Cognitive Domains

The cognitive or behavioral impairment must involve at least two of the following domains 1:

• Memory impairment: Inability to acquire and remember new information, repetitive questions, misplacing belongings, forgetting appointments 1
• Impaired reasoning and judgment: Poor understanding of safety risks, inability to manage finances, poor decision-making 1
• Visuospatial dysfunction: Inability to recognize faces or objects, difficulty with spatial orientation 1
• Language impairment: Difficulty finding words, speech hesitations, writing errors 1
• Personality or behavioral changes: Mood fluctuations, apathy, social withdrawal, loss of empathy, socially unacceptable behaviors 1

Epidemiology and Impact

Dementia affects 47 million people worldwide and is expected to reach 131 million by 2050. 1 In the United States, prevalence is 15% in people over 68 years of age, and it constitutes the fifth leading cause of death in patients over 65 years 1. The condition leads to great morbidity and mortality, posing diagnostic and management challenges for patients, families, and clinicians 1.

Common Etiologies

Multiple diseases cause the dementia syndrome 1:

• Alzheimer disease (AD): The most common cause, accounting for 50-70% of all dementia cases 1
• Vascular dementia (VaD): Often co-occurs with other progressive cognitive disorders 1
• Dementia with Lewy bodies (DLB): Part of the Lewy body disease spectrum 1
• Frontotemporal dementia (FTD): Occurs earlier than other forms and progresses rapidly 1
• Mixed dementias: Commonly involves Alzheimer disease with cerebrovascular pathology 1, 2
• Other causes: Normal pressure hydrocephalus (NPH), infectious, autoimmune, toxic etiologies, traumatic brain injury 1

Distinction from Mild Cognitive Impairment

Mild cognitive impairment (MCI) differs from dementia in that patients have impairment in one or several cognitive domains but of a mild degree, interfering minimally with daily living and functioning 1. MCI represents a symptomatic predementia phase, particularly for Alzheimer disease 1. The differentiation rests on determining whether cognitive impairment is severe enough to significantly affect social or occupational function 1, 2.

Clinical Significance

Dementia is fundamentally a clinical diagnosis requiring clinician judgment 1. It is not normal healthy aging but rather a malignant and devastating condition leading invariably to dependence and death 1. The syndrome encompasses a spectrum of severity from mildest to most severe stages, with progressive functional losses and difficulties in communication and social interaction that worsen as severity increases 1.