Does a diagnosis of major neurocognitive disorder replace a diagnosis of dementia in geriatric patients with cognitive decline?

Major Neurocognitive Disorder vs. Dementia: Terminology and Diagnostic Distinctions

Major neurocognitive disorder (major NCD) is the DSM-5 term that replaces "dementia," but they refer to the same clinical entity—the key difference is nomenclature, not diagnostic criteria. 1, 2, 3

Terminology Evolution

• The DSM-5 introduced "major neurocognitive disorder" to replace the term "dementia" that was used in DSM-IV, representing a shift in diagnostic language rather than a fundamental change in what is being diagnosed 1, 4

• This terminology change was designed to be less stigmatizing for patients and families, and to better accommodate neurodegenerative cognitive disorders where memory impairment is not the predominant feature 4

• In clinical practice, both terms remain in use: "major NCD" appears in formal DSM-5 diagnostic coding, while "dementia" continues to be widely used in clinical guidelines, research literature, and patient communication 2, 3

Core Diagnostic Requirements (Identical Across Both Terms)

Both major NCD and dementia require:

• Significant cognitive decline from a previous level of performance in one or more cognitive domains (complex attention, executive function, learning and memory, language, perceptual-motor, or social cognition) 3

• Functional impairment in everyday activities—the cognitive deficits must interfere with independence in instrumental activities of daily living (IADLs) such as managing finances, medications, transportation, household tasks, cooking, or shopping 5, 6, 3

• Insidious onset and progressive decline documented through patient/informant history or serial cognitive assessments 5

• Absence of delirium as the primary explanation for cognitive impairment 5

Key Diagnostic Distinction: Major NCD vs. Mild NCD

The more clinically relevant distinction introduced by DSM-5 is between major and mild neurocognitive disorder:

• Major NCD (dementia): Cognitive decline that causes loss of independence in everyday functional abilities—patients require assistance with IADLs 1, 7, 3

• Mild NCD: Noticeable cognitive decline that does not interfere with independence in daily activities, though patients may need to exert compensatory effort or use strategies to maintain function 1, 7

• Mild NCD corresponds closely to the research concept of mild cognitive impairment (MCI), though the DSM-5 criteria provide more structured diagnostic thresholds 5, 1

Practical Diagnostic Approach

When evaluating cognitive decline, the critical determination is functional status:

• Obtain collateral history from a reliable informant using validated tools (AD8, IQCODE) to document decline in accustomed activities 6

• Systematically probe specific IADLs: Can the patient independently manage finances, medications, transportation, household tasks, cooking, and shopping at their previous level? 6

• If independence is preserved despite cognitive decline → Mild NCD 1, 7

• If independence is lost and assistance is required → Major NCD (dementia) 5, 7, 3

• Document objective cognitive impairment in one or more domains using validated instruments (MoCA for comprehensive assessment, complemented by Clock Drawing Test) 5, 6

Clinical Implications

• The shift to "major NCD" terminology does not change treatment approaches, prognosis discussions, or management strategies—these remain identical to traditional dementia care 2, 3

• The addition of "mild NCD" as a formal diagnostic category provides a framework for identifying patients at risk for progression who may benefit from closer monitoring and future disease-modifying therapies 1

• Approximately one-third of patients with mild NCD (particularly multiple-domain subtypes) progress to major NCD within 2 years, while single-domain mild NCD patients may revert to normal 7

Common Pitfalls to Avoid

• Do not assume the terminology change represents a different disease entity—major NCD and dementia are synonymous 1, 2, 3

• Do not diagnose major NCD based solely on cognitive test scores without documenting functional impairment in daily activities 6, 3

• Do not overlook the importance of serial assessments over time to document progressive decline, which distinguishes neurodegenerative disease from static conditions 5, 6

• Do not attribute acute cognitive changes to major NCD without excluding reversible causes (infections, metabolic disorders, medications, cerebrovascular events) 8