Lecture 16: The Aging Brain

What is normal cognitive aging?

intelligence is split into crystallised intelligence (knowledge or language accumulation - assessed using vocab, or semantic ) and fluid intelligence (associated with solving novel problems or processing new information)
As you age, there tends to be a drop in fluid intelligence.
Note that really severe cognitive decline can result in dementia
Dementia is not a part of normal aging - cognitive decline to the point that you cannot function independently.

What is the difference between Alzheimer's disease and dementia?

Alzheimer's disease is a form of dementia. (commonly diagnosed 65)
Alzheimer's disease is a more genetically linked form of dementia.
Dementia = confusion, memory loss - in the DSM is categorised as a mild neurocognitive disorder or serious

What are the different types of dementia?

Describe Alzheimer's?
Alzheimer's - strong genetic component - APOE s4 allele - 1 - (1-3 fold increase), 2 - (12 fold increase) - progressive and gradual - clear neuropathology - associated with beta-amyloid plaque and neurofibrillary tangles
Biomarkers – proposed staging technique to see changes in the brain leading to alzheimer's - stages associated involve increasing amount of amyloid development.

Describe vascular dementia

Damages to blood vessels in parts of the brain. 5-10% associated with strokes.

Describe frontotemporal demental

Has two types - normally associated with early onset dementia
Behavioural - impacting your capacity to control conduct
Primary progressive - effects ability to control language.

Describe dementia with lewy bodies

Dementia with lewy bodies - associated with meeting the DSM criteria for mild neurodegenerative disorder
May have motor deficits, REM sleep disorder, sensitivity to antipsychotic medication

What are the symptomatic differences between dementia?

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What should you note about mixed pathology?

People normally present with mixed pathology with people showing brain changes.
More than 50% of people - have mixed dementia - higher levels communicity.

What are responsive behaviours?

Other than cognitive changes, people with dementia also experience changes in their behaviours. - a person's way of communicating distress, frustration, or unmet needs, and can include agitation, aggression, wandering, anxiety, and hallucinations.
Vagueness in everyday conversation, apparent loss of enthusiasm, taking longer to do tasks, emotional instability.

Can you treat dementia ?

You can manage and treat the cognitive and BPSD,
However, there are some drugs that may help by removing amyloid plaques
Note that brain pathologies like vascular damage or Lewy bodies.
20% of people who take these drugs have brain bleeds
Efficacy is uncertain,
Monthly or fortnightly infusions are needed. Frequent MRIs are needed to check in.

What are some dementia risk factors?

Age is the biggest risk factor for dementia - occurring in 1 in 10 people aged 65 and over, and 3 in 10 people at age 85.
Modifiable risk factors -
Medical/cardiometrabolic risk factors - diabetes, high cholesterol, hypertension (complex relationship), obesity in middle age (weight tends to drop before diagnosis)
Unclear mechanisms between risk factor and other
Sensory - hearing loss and vision loss
Mechanisms - (1) common process which can generate both (2) loss leads to dementia (3) loss leads to social isolation which leads to dementia
Life sensory - physical inactivity, heavy alcohol consumption, smoking, social isolation, depression, traumatic brain injury, air pollution.

Does treatment of these risk factors decrease the risk of dementia ?

Not a lot of evidence for it. HOWEVER
Reducing alcohol consumption to light and moderate - J shaped curves. - reason unclear
Physical activity - doing some is better than none.
Mediterranean-like diets associated with greater dementia risk reduction.
Depression - some evidence to support
Social isolation - weak evidence.

Describe multidomain intervention?

note that many risk factors overlap between cardiovascular disease and dementia - so interventions targeting both physical activity and healthy diets is better - large RCT found small but moderate effect of multi-domain interventions on risk of dementia.

Note about education?

Education is a strong protective factors against dementia
Linked to cognitive stimulation and cognitive training - evidence says that this may help to decrease dementia risk
These may impact dementia risks via its contribution to cognitive reserves.

What is nun study/ katzmen ?

recruited 679 american roman catholic sisters, Underwent cognitive assessment and brains were donated after they died. - found that all combination of alzheimer's and cognitive performance can exist togher
Argues that there is a cognitive resilient.

What are some mechanisms of cognitive resilience?

Brain reserve - resilient individuals have big brain = less impact on dementia - passive - measured at one time point -
Brain maintenance - individual brain volumes and they aint this for their whole life - active - measured across the lifeline
You cannot test the difference using cross-sectional designs.

What is cognitive reserve?

argues that people with higher cognitive reserve that can resist decline up to a certain point - purely theoretical model
Differences in cognitive reserve = how dementia has different impacts
Mechanisms of cognitive reserve
Neural compensation - with higher reserve allows recruiting brain structure of networks not normally found in individual without pathology
Neural efficiency - higher cognitive reserve could be associated with more efficient networks
Neural capacity - higher cognitive reserve allows for more brain network to be activating to keep performing a task in the face of increasing demands.

What is the relationship between cognitive reserve and dementia

Solden et al 2017, tested 4 x theory
Found that
Cognitive reserve and neuropathology both predicted dementia
Cognitive reserve did moderate the effect of neuropathology
Cognitive reserve - does not affect the accumulation of pathology
Cognitive reserve did modify the effect of age on dementia risk.
Higher levels of cognitive reserve associated with a delayed onset
Suggests separate mechanisms between the two.
Suggest that higher cognitive reserve was associated with steppe decline after becoming symptomatic

What did nelson et al 2021 find?

Found that cognitive reserve delayed the effect of dementia, used statistics to compare performance with or without dementia, AND a proxy measurement of cognitive reserve to predict risk.
Found that there there was no difference in the way both approaches attempted to judge the effect of cognitive reserve on dementia
Limitations to both approaches however.

Why do some people experience cognitive decline and other don’t?

Resilience - being about to cope with pathology
Resistance - refers to avoiding pathology .