HC12: Prevention
What we have learned during the last topics about dementia, is that for none of them is a
cure or an intervention that can stop the progress of deterioration/decline. Therefore, there is
an increasing interest in new interventions to try and prevent becoming ill.
There are some issues:
There are individual differences in vulnerability: some people have no dementia
symptoms despite an extensive brain pathology.
Modifiable risk factors for dementia: diet, exercise, leisure activities. Can these
factors reduce the risk and for some people prevent dementia?
There seem to be some people who have extensive brain pathology, the kind of pathology
which is associated with AD or with VAD or DLB, but they don’t seem to have any symptoms
or cognitive impairments (left pie chart).
>50% cognitively normal persons had dementia pathology
What it illustrates is that there is no one to one relationship between brain function
(cognition) and brain structure (pathology/atrophy). There must be characteristic of a person
than protect against brain changes which can help to prevent dementia. Not that you can
prevent the brain disease, but it may help to understand the symptoms, because it is not
necessarily the brain pathology that makes you so sick and disables, but the symptoms do!
A well-known explanation that has been put forward is the idea of the cognitive reserve
(CR) theoretical model that explains the discrepancy between dementia pathology in the
brain and absence in symptoms
Brain attempts to cope with brain damage: there is damage, but still somehow the
brain attempts to cope with that and still manages to function good enough.
o Using preexisting cognitive processing or compensatory approaches
o High CR – better able to copy with same amount of brain damage than low
CR
o Someone with a higher CR will show fewer symptoms while having the same
amount of damage.
CR is not a specific skill and can’t be tested in one single test. Because the idea of CR would
affect all cognitive functions and not just memory, but also speed, language, flexibility etc.
That is important to remember!
, CR is an effect of brain function, although it is unclear how it works precisely. It would be in
contrast with the brain reserve model.
Brain reserve model reserve effect of brain size, number of neurons. A bigger brain
protects longer against progressing pathology.
There is more you can do to manipulate CR than you can manipulate brain reserve.
CR is not the same as adjusting for education, although it is related to education:
At baseline, before onset of pathology:
o 70-year-old with 8 years of education will recall fewer words than a 70-year-
old with 19 years of education. Therefore, the baselines are different
After onset of pathology:
o 19 years of education needs to sustain more pathology than 8 years of
education to reach impaired range (to drop below the cut off score for
cognitive impairment)
CR = why would a person with 19 years of education remain at baseline level longer than a
person with 8 years of education? What contributes to CR?
Evidence for education, occupation, leisure activities
o Higher education and higher occupation both contribute to the CR
Study of Stern et al., 1994:
Education: high > 8 years, low < 8 years
Low occupation: unskilled, skilled trade, clerical
High occupation managerial, professional
They simply counted the incidence of people within that group who developed dementia.
The relative risk factor
was: the persons with
low occupation or low
education were twice as
likely to be diagnosed
with dementia than those
with high occupation or
education. This clearly
illustrates the risk!
Reversely this means that those in the high groups somehow seem to be protected.
We also saw this in MCI, those with more years of education have a lower prevalence for
MCI (both for men and women). There were fewer symptoms in the group with more years of
education.
It is not just education, but also activities outside of work:
Community sample, followed up over 7 years
More leisure activities, reduced risk of dementia
Most strongly associated with reduced risk were:
o Intellectual activities (e.g., reading, playing cards)
o Physical activities (e.g., walking, exercise)
