Dementia, a term encompassing various neurological conditions, is primarily characterized by a decline in cognitive function resulting from physical changes in the brain, distinguishing it from mental illnesses. In the realm of diagnostic classifications, the Diagnostic and Statistical Manual of Mental Disorders, 5th Edition (DSM-5), categorizes dementia under the umbrella of Neurocognitive Disorders (NCDs). This broad NCD category is further divided into Minor NCD and Major NCD, reflecting the spectrum of cognitive impairment severity. The term “neurocognitive” underscores the origin of these disorders in brain disease and disrupted brain function, leading to noticeable cognitive deficits.
Within the NCD spectrum, the primary clinical feature is an acquired decline in cognitive function, not one that has been present since development. This impairment can manifest in various cognitive domains, including attention, executive function (planning, decision-making), inhibition, learning, memory, language, visual perception, spatial abilities, and social cognitive skills. Understanding these distinctions is crucial for accurate dementia diagnosis using DSM-5 criteria.
Decoding Neurocognitive Disorder (NCD) in DSM-5
Neurocognitive Disorder (NCD), as defined in DSM-5, represents a group of conditions where the core deficit lies in cognitive function. This decline is acquired, meaning it represents a change from a previous level of cognitive ability, rather than a developmental issue. The impact of NCDs can be seen across a range of mental processes, affecting how individuals process information, remember events, use language, and interact socially. The DSM-5 classification helps clinicians differentiate between the severity of cognitive impairment, guiding diagnosis and care planning.
Minor Neurocognitive Disorder (Minor NCD) – Prodromal Stage
Minor Neurocognitive Disorder, sometimes referred to as Mild Cognitive Impairment (MCI) or Prodromal Dementia, signifies an early stage of cognitive decline. According to DSM-5, the criteria for Minor NCD include:
- Evidence of Modest Cognitive Decline: This is based on concerns reported by the individual themselves, a knowledgeable informant (like a family member), or observed by a clinician. This decline is also substantiated by neurocognitive test performance, typically falling between one and two standard deviations below normative values (roughly between the 3rd and 16th percentiles). This indicates a measurable decline from prior cognitive function.
- Preserved Independence: Despite cognitive deficits, individuals with Minor NCD maintain independence in daily life, particularly in instrumental activities of daily living (IADLs) such as managing finances or medications. They may require greater effort or compensatory strategies, but they can still manage these tasks independently.
- Not Due to Delirium: The cognitive deficits must not occur exclusively during an episode of delirium, which is a state of acute confusion and fluctuating cognition.
- Not Primarily Attributable to Other Mental Disorders: The cognitive decline should not be primarily explained by another mental disorder, such as major depressive disorder or schizophrenia, although these conditions can co-exist.
Major Neurocognitive Disorder (Major NCD) – Dementia
Major Neurocognitive Disorder, which aligns with the common understanding of dementia, represents a more significant stage of cognitive decline. The DSM-5 criteria for Major NCD are:
- Evidence of Substantial Cognitive Decline: Similar to Minor NCD, this is based on reports from the individual, an informant, or clinical observation. However, the decline is more pronounced, with test performance typically falling two or more standard deviations below normative values (below the 3rd percentile). This signifies a significant departure from previous cognitive abilities.
- Interference with Independence: Crucially, the cognitive deficits are now severe enough to interfere with independence. Individuals with Major NCD require assistance with instrumental activities of daily living and may eventually need help with basic activities of daily living as well.
- Not Due to Delirium: As with Minor NCD, the cognitive deficits are not exclusively due to delirium.
- Not Primarily Attributable to Other Mental Disorders: The cognitive decline is not primarily explained by another mental disorder, though co-occurrence is possible.
Exploring the Six Cognitive Domains in DSM-5
The DSM-5 outlines six cognitive domains that are assessed in the diagnosis of both Minor and Major NCD. These domains provide a framework for understanding the specific cognitive functions affected by dementia:
Complex Attention
This domain encompasses sustained attention (maintaining focus over time), divided attention (attending to multiple stimuli simultaneously), selective attention (focusing on relevant stimuli while filtering out distractions), and information processing speed.
Warning signs: Individuals may exhibit increased difficulty concentrating in environments with multiple stimuli, such as when the TV is on or during conversations. They may also struggle to hold new information in mind, like recalling recently given phone numbers or instructions.
Executive Function
Executive function refers to higher-level cognitive processes essential for goal-directed behavior, including planning, decision-making, working memory (holding and manipulating information in mind), responding to feedback, error correction, overriding habits, and mental flexibility.
Warning signs: Individuals may become unable to manage both familiar and complex tasks at work or home. They might increasingly rely on others to plan daily activities or make decisions. Problems with abstract thinking, decreased initiative, and impaired judgment are also common indicators.
Learning and Memory
This domain involves various types of memory, including immediate memory (very short-term recall), recent memory (recall over minutes to hours, including free recall, cued recall, and recognition memory), and long-term memory (memory for events and information over longer periods).
Warning signs: Repetitive speech during conversations, often repeating the same stories or points, is a key sign. Difficulty keeping track of short lists, like shopping lists or daily plans, and needing frequent reminders about tasks or orientation, along with confusion about time and place, and repetitive behaviors, are also indicative of learning and memory impairment.
Language
Language function includes both expressive language (the ability to produce language, including naming objects, fluency of speech, grammar, and syntax) and receptive language (the ability to understand language).
Warning signs: Significant difficulties with expressing oneself verbally or understanding spoken or written language are warning signs. Individuals might use general terms like “that thing” or “you know what I mean” due to word-finding difficulties. In more severe cases, they may struggle to recall the names of close friends and family.
Perceptual-Motor Function
This domain encompasses the integration of perception and motor skills, necessary for activities like picking up the phone, handwriting, using utensils, and navigating physical spaces.
Warning signs: Difficulty with previously familiar activities, such as using tools, driving a car, or navigating familiar environments, suggests impairment in perceptual-motor function.
Social Cognition
Social cognition involves the ability to understand social cues, recognize emotions in oneself and others, regulate behavior in social situations, and understand social appropriateness in terms of dress, grooming, and conversation topics.
Warning signs: Changes in social behavior, such as showing insensitivity to social norms, making decisions without considering safety, or becoming socially withdrawn and isolated, can be indicative of impaired social cognition. Individuals often have limited insight into these changes.
Dementia Diagnosis: Assessment and Evaluation
Diagnosing dementia is a complex process. There isn’t a single definitive test; instead, diagnosis relies on a comprehensive assessment that considers behavioral, functional, and psychosocial changes, alongside radiological and laboratory findings. The entire evaluation process may span several months to ensure accuracy.
Cognitive assessment is crucial when there’s any indication or suspicion of cognitive impairment. This initial step determines whether further, more in-depth evaluation is necessary. Gathering a detailed patient history from an “informant”—someone who knows the patient well and has observed their cognition and daily functioning over time—is essential. Informants are typically partners, family members, or close friends.
During informant interviews, key areas to explore include:
- Risk factors: History of vascular disease, alcohol use, head injury, mood disorders, behavioral and psychological symptoms, recent illnesses, and medication use.
- Activities of Daily Living (ADL) and Instrumental ADLs (IADLs): Assessments of functional abilities, cognitive complaints, mood changes, driving ability, and safety awareness.
- Behavioral Changes and Functional Decline: Understanding the onset and progression of these changes over time.
Tools like the AD8 Dementia Screening Instrument are valuable for structured informant interviews. Commonly used cognitive assessment tests aid in quantifying cognitive function; however, the choice of tests should be tailored to the individual patient and the healthcare setting. While not detailed here, the International Classification of Diseases (ICD-11) also provides a coding system for dementia, complementing the DSM-5 diagnostic framework. Information on ICD-11 codes can be found on the World Health Organisation’s ICD website.
In conclusion, diagnosing dementia using DSM-5 criteria involves a nuanced approach that considers both the severity and nature of cognitive decline across multiple domains. Comprehensive assessment, incorporating informant reports and cognitive testing, is paramount for accurate diagnosis and effective patient care.
