If two people were to suffer from a stroke of the same extent and in the same location, it would seem logical that the impact would be of a similar severity. However, this is not always the case so, what does the impact depend on?
The explanation for why some people who are the same age and have similar neuronal damage do not show the same symptoms of cognitive damage has to do with cognitive reserve. This is defined as:
The ability to trigger alternative neuronal networks if there is a need to offset the severity of symptoms of illnesses or processes such as age deterioration or illnesses’ like Alzheimer’s.
Cognitive reserve has a biological substrate based on innate brain characteristics such as size, neuronal count and density or the quality and quantity of synapses and an acquired substrate that depends on a person’s environment and abilities that they have developed throughout their life. This helps to distinguish two types of cognitive reserve: active and passive.
Or brain reserve: this can be defined as the physical size of the brain (the number of neurons in the brain). Studies have shown that people with bigger brains (having more neurons or more synapses) are more resistant to damage because a large portion of the brain continues to function properly after the initial damage. The term passive is used because we do not have control over the size of our brains.
Or simply cognitive reserve: this refers to the brain’s ability to compensate for the changes in the brain structure related to age or a certain pathology. Active reserve avoids the depletion of the brain’s ability to function and the people of an older age or with brain damage show better cognitive functioning than expected because their neuronal networks are able to start processes for compensation.
So, can cognitive reserve prevent neurodegenerative diseases such as Alzheimer or Senile Dementia?
Although there are currently no conclusive studies that show that cognitive reserve prevents the appearance of neurodegenerative diseases but what has been shown is that cognitive reserve seems to be associated with delay in symptoms. Meaning, high cognitive reserve does not stop neurodegenerative processes but it prevents the appearance of symptoms.
Therefore, a brain that has a large cognitive reserve is capable of slowing down the appearance of symptoms related to dementia, but not eliminating them as it is not related to the disease itself but rather the symptoms. Although when the first symptoms do appear, they are more intense because the brain seems to reach a point where it is no longer capable of compensating for the damage.
Studies have also shown which factors are related to a larger cognitive reserve, highlighting that people with a higher educational level, active working life and more participation in stimulating and leisure activities show a higher cognitive reserve. These factors are directly related to socio-economic level and it is difficult to differentiate the influence of each one.