General Considerations
- See also the broader discussion of Aging and Cognition
- Many aspects of memory deteriorate w/ age
- Decline affects recent memory more than immediate or remote
- Ability to encode, store, and recall info is typically reduced in older adults; that is, memory processes become less effective, although the content of memory (knowledge) can continue to increase
- Four different levels of memory functioning can be identified during life span
- Peak performance reached at some point during adulthood; may be maintained by rare individuals who are said to enjoy superior aging
- Age-appropriate decline; scores remain w/in range that is average for age
- terms used here include age-associated memory impairment, benign senescent forgetfulness, and age-associated cognitive decline
- Mild Cognitive Impairment: significantly below age-adjusted norm on standardized test, but without ADL impairment
- Dementia: deterioration reaches level where interferes w/ ADLs
Normal Aging
- Vast majority of neurons grow to be as old as owner
- thus, each neuron exposed to cumulative effect of bio wear and tear throughout life
- Aging depends on interaction of 3 variables:
- time
- genetic background
- stochastic encounters w/ diverse events such as stress, hypertension, oxidation, trauma, etc.
- Age-related changes are not necessarily intrinsic to aging – ie, aging may not cause the events but may increase the probability of encountering them; differentiating inevitable consequences of aging and cumulative (BUT preventable) impact of stochastic events embedded w/in time is very complex
- Normal aging characterized by increased interindividual variability
- Biological Components
- Healthy aging ass’d w/ small loss of brain volume, but rate doesn’t accelerate w/ advancing age
- Traditional view that aging is ass’d w/ massive loss of neurons is wrong
- Cortical myelination seen to increase into 7th decade!
- Aging brain retains considerable potential for structural plasticity
- In sum, on AVERAGE
- advancing age increases risk for losing neurons, synapses, transmitters, and cognitive acuity
- but, many “age-related” changes might reflect preventable stochastic events
- nonetheless, greatly enhanced vulnerability for dementing diseases
Mild Cognitive Impairment
Definition
- Refers to transitional state between normal cognitive aging and mild dementia
- It includes subjective memory complaint, corroborated by objective memory impairment on standardized test, but adequate general cognitive ability and ADLs ok
- Since other forms of MCI exist, MCI emphasizing memory loss is termed Amnesic MCI
Heterogeneity
- Individuals who present w/ MCI will not necessarily have same outcome since have different causes (could be DLB, FTD, etc.)
Progression
- Individuals w/ MCI evolve to dementia at rate of 10-15% per year (normal is 1-2% per year)
- variables that predict more rapid decline include apolipoprotein E4, atrophic hippocampi on MRI
Treatment
- No effective treatment currently known, but cholinesterase inhibitors, anti-inflammatory agents, and anti-oxidants (eg, vitamin E) all theoretically make sense