Cognitive Decline

What happens to the brain in older age?

• Brain mass shrinks

• The outer surface (cortex) thins

• White matter decreases

• Chemical messengers decrease

• Atrophy occurs in key cognitive/social areas:

1. Grey matter structure - superior frontal cortex, middle frontal cortex, superior parietal cortex

2. Structural connectivity - superior white matter tracts, anterior white matter tracts

3. Functional connectivity - within-network connections

• Perceptual abilities decline across multiple modalities:

1. Sight impairments with age

2. Hearing impairments with age

• Executive function skills decline in old age; memory, reasoning, spatial visualisation, speed

What is cognitive impairment?

• A decline in one or more cognitive functions compared to a previous level

• Domains affected may include:

1. Memory

2. Attention

3. Language

4. Executive function

5. Visuospatial skills

• It is not a diagnosis - it is a descriptive term

• Ranges from mild (subtle difficulties) leads to severe (loss of independence)

What is characteristic of Mild Cognitive Impairment (MCI)?

• Measurable decline

• Daily function largely preserved

• Often a transitional stage

What is characteristic of Dementia?

• Significant impairment in >2 domains

• Interferes with independence

• Progressive (e.g. Alzheimer’s disease)

What is the DSM-5 criteria for Mild Neurocognitive Disorder?

• Evidence of modest cognitive decline from a previous higher level of performance in one or more cognitive domains

• Cognitive deficits do not interfere with independence in everyday activities

• Greater effort and compensatory strategies are not needed

• Neuropsychological testing 1-2 standard deviations below norms (3^rd-16^th percentile)

What is the DSM-5 criteria for Major Neurocognitive Disorders?

• Evidence of significant cognitive decline from a previous higher level of performance in one or more cognitive domains

• Cognitive deficits do not interfere with independence in everyday activities

• Requiring assistance in Instrumental Activities of Daily Living (IADL)

• Neuropsychological testing typically 2 or more standard deviations below norms (3^rd percentile or below)

What is the DSM-5 criteria for dementia?

• Evidence of significant cognitive decline from a previous level of performance in one or more cognitive domains:

• Learning & memory, language, executive function, complex attention, perceptual motor function, social cognition

• The cognitive deficits interfere with independence in everyday activities – at minimum, assistance should be required with complex instrumental activities of daily living, such as paying bills or managing medications

• The cognitive deficits do not occur exclusively during the context of delirium

• The cognitive deficits are not better explained by another mental disorder e.g. major depressive disorder, schizophrenia

What are some primary causes of neurocognitive disorders?

• Alzheimer’s disease

• Frontotemporal or mixed dementia

• Dementia with Lewy Bodies

• Vascular Cognitive Impairment

What are some reversible causes of neurocognitive disorders?

• Depression

• Vitamin deficiencies (B12, B1)

• Severe anaemia

• Medication

What are some secondary causes of neurocognitive disorders?

• Traumatic brain injury (TBI)

• Chronic traumatic encephalopathy

• Movement disorders

• Substance abuse

• HIV infection

What is the Montreal Cognitive Assessment (MoCA)?

• Screening tool used for Mild Cognitive Impairment (MCI)

• Developed by Dr. Ziad Nasreddine

• Widely used in clinical settings

• Detects early cognitive decline

• Covers multiple cognitive domains

Who is the MoCA used for?

• The MoCA was originally validated for 55-85-year-olds, which is the most commonly validated age range

• Later studies have validated it for use with a wider age range (18+)

• Melikyan et al. (2021) validated the test for ‘oldest-old’ populations (90+), with the MoCA-22 removing visual subtests

When is the MoCA used?

• It is rarely used as a standalone diagnostic tool, but rather as a critical, early component in a longer diagnostic pathway to decide which patients require further, more in-depth assessment:

1. Triage and screening - healthcare providers use MoCA to screen patients 50+ or those reporting memory issues

2. Baseline setting - memory clinics using MoCA as a baseline to determine need for further investigation

3. Longitudinal monitoring - it can be used repeatedly ton track cognitive decline

• A low MoCA score alone does not provide dementia, it only warrants further investigations

What other measures are used alongside the MoCA?

• Questionnaires on social functioning and activities are used to evaluate impairment of daily activities

• Family history of MCI or dementia and reports from close others, patients’ self-awareness of cognitive decline is often poor

• Neuropsychological testing, using a battery of tests to determine specific areas

• Blood work can be used to reveal blood changes (e.g. thyroid or vitamin issues)

• Brain imaging (MRI or CT) can rule out reversible causes of cognitive decline

Who can administer the MoCA?

• Any clinician, care provider, or researcher can administer the MoCA by following the official administration and scoring instructions

• Researchers can be trained locally and use the test freely

• Clinicians must complete formal training and certification to interpret results

What is involved in the MoCA test structure?

• 30-point test

• Takes approximately 10 minutes

• Paper-based or digital

• Higher score indicates better cognitive function, while a lower score may indicate cognitive impairment

What is involved in the ‘visuospatial/executive’ cognitive domain?

• Consists of three tasks

• Total of 5 points awarded

• Includes tasks such as clock drawing, cube-copying, trail-making tests

What is involved in the ‘naming’ cognitive domain?

• Consists of three tasks

• Total of 3 points awarded

• Tasks may involve seeing an image of an animal and assigning the correct name

What is involved in the ‘memory’ cognitive domain?

• Consists of two tasks

• No points awarded (items tested later)

What is involved in the ‘attention’ cognitive domain?

• Consists of three tasks

• Total of 6 points awarded

• Tasks may involve serial subtraction, or being asked to repeat a series of numbers in a forwards or backwards order

What is involved in the ‘ language’ cognitive domain?

• Consists of two tasks

• Total of three points awarded

• Tasks test how fluently people repeat a sentence, or saying words that match a given theme (e.g. words beginning with T)

What is involved in the ‘abstraction’ cognitive domain?

• Consists of two tasks

• Total of 2 points awarded

• Tasks involve finding similarities between words (e.g. between train-bicycle, ‘both are vehicles’ and ‘means of transportation’ are correct, but ‘they both move’ would be too vague)

What is involved in the ‘delayed recall’ cognitive domain?

• Consists of one task

• Total of 5 points awarded

• Full points awarded if patient can recall 5 words correctly and in a timely manner

What is involved in the ‘orientation’ cognitive domain?

• Consists of one task with 6 questions

• Total of 6 points awarded

• Date, day, place, and city must be correct

• Clinical interpretation:

1. Time is often affected earlier

2. Place tends to be preserved until later

3. Pattern helps distinguish delirium vs dementia vs normal ageing

Interpretation of MoCA Scores

• 26 - 30 - considered normal

• 18 - 25 - demonstrates mild impairment

• 10 - 17 - demonstrates moderate impairment

• <10 - demonstrates severe impairment

What did Wei et al. (2024) find?

• Approximately 47% of MoCA score is explained by age and education, proposing a cutoff of 22 as optimal to detect vascular cognitive impairment

How was the MoCA developed and validated?

• Sample included 94 with MCI, 93 with mild dementia, and 90 healthy older people

• MoCA sensitivity (i.e. identifying MCI and AD as <26) was excellent (90% and 100% respectively)

• MoCA specificity (i.e. identifying healthy controls as >=26) was very good to excellent specificity (87%)

• MoCA is equivalent across language forms (English vs. French)

• Test-retest reliability was assessed, and correlation between tests were very high (r = .92)

• Internal consistency was good, with different MoCA tasks (memory, attention, language etc) coherently measure overall cognition

Mini-Mental State Examination (MMSE) specificity and sensitivity

• MMSE sensitivity (i.e. identifying MCI and AD was <26) was poor (18% and 78% respectively)

• MMSE specificity was excellent, correctly identifying 10% of the NCs

• MoCA and MMSE scores are highly correlated

• The large majority of NC participants scored in the normal range, and the large majority of AD patients scored in the abnormal range on both MMSE and MoCA

• In contrast, 73% of MCI patients scored in the abnormal range on the MoCA but in the normal range on the MMSE

What did Lebedeva et al. (2016) find?

• MoCA scores are generally stable across online and in person contexts

• But, the online MoCA has limited generalisability across language-speaking cohorts

What is an example of compromised MoCA testing?

• In 2018, Donald Trump announced his perfect score on the MoCA

• Researchers and doctors warned the test’s effectiveness was compromised due to widespread media publication of its questions

• The intense publicity created a learning effect, potentially making the screening tool less reliable

• American Academy of Clinical Neuropsychology responded by protecting test information from non-psychologists

What are strengths of the MoCA?

• Good sensitivity to Mild Cognitive Impairment (more accurate than MMSE)

• Quick to administer

• Covers multiple domains

• Free of charge

• Can be repeated on the same patient to track change over time

• Validated across many conditions

What are limitations of the MoCA?

• Less specific for dementia sub-types

• Not a stand-alone diagnostic tool

• Score is influenced by education and culture

• Official MoCA certificate required to administer for clinical use

• Score can be influenced by non-cognitive factors

• Some scoring is subjective

• Repeat exposure to the MoCA can lead to practice effects

What are some ethical considerations of the MoCA?

• Informed consent and understanding of purpose (testing without proper explanation can undermine autonomy)

• Impact on patient wellbeing (poor performance can affect self-esteem or identity)

• Cultural and education bias (risk of false positives in low/education/non-native speakers)

• Confidentiality and sensitive information (MoCA scores may have implication for daily functioning)

What cognitive domains is the dorsolateral prefrontal cortex associated with?

• Executive functioning and planning e.g. trail making, abstraction

What cognitive domains is the hippocampus/medial temporal lobe associated with?

• Episodic memory e.g. delayed recall

What cognitive domains is the temporal lobe associated with?

• Language e.g. naming, sentence repetition

What cognitive domains is the parietal occipital lobe associated with?

• Visuo-spatial abilities e.g. clock-drawing, cube copying

How do we interpret MoCA scores?

1. Look at total score

• >26 is typically normal

• <26 means possible impairment but not diagnostic

2. Examine pattern of errors

• Executive task errors → frontal dysfunction

• Memory errors → encoding vs retrieval

• Language → temporal involvement

3. Consider patient background

• Education level

• Occupational/baseline ability

• Functional independence

4. Form interpretation

• Normal Ageing

• Mild Cognitive Impairment

• Possible dementia, requiring further testing