The Nun Study
Between 1991-2002, a study was conducted on 470 nuns from the School Sisters of Notre Dame (USA). All of the nuns were older than 75, with an average age of 84. Autopsies showed that while most of their brains had Alzheimer’s pathology, few of the nuns had demonstrated the behavioural changes associated with the physical progression of the disease. The conclusion extrapolated by the study was that the diverging clinical outcomes (pathology v’s behaviour) was consistent with the cognitive reserve hypothesis. More information can be found at ....
Video www.youtube.com/watch?v=nw2lafKIEio or search youtube for “nun study video”
Scientific Publication of the “Nun Study” http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2734290/
What is Cognitive Reserve ?
Medically, cognitive reserve can be defined as a hypothesis for investigating the difference in pathology (physical illness) v's symptoms (behaviour). Cognitive reserve is the ability of a person to tolerate physically advancing brain disease without demonstrating signs of dementia.
Two people who appear behaviourally similar can have widely different levels of underlying physical brain degeneration. Diagnosing either a normal ageing person or a dementia patient may be accompanied by a comparatively unrelated amount of physical brain illness. Measuring cognitive reserve therefore becomes an important component of diagnosing the onset of dementia. Once formally classified, this type of evaluation will be fundamental for diagnosis, measuring progression and assessing the effect of interventions.
It is well known that individuals vary considerably in the extent of their memory, cognitive skills, and symptoms of dementia as they age. It is believed that novelty and mental stimulation over the duration of one’s life builds up the capacity for cognitive reserve. It is thought that different types of mental effort builds cognitive reserves in different parts of our brain. This is because cognitive decline varies by individual and is not evenly distributed across all areas of brain functions. Understanding how cognitive reserve as it applies to the whole brain or parts of it is likely to play a big role in this aspect.
How Does Cognitive Reserve Work ?
There are a number of ideas that scientists are investigating as to how cognitive reserve might work :
· a greater number of neurons existed earlier in life
· a greater number of neuron connections (synapses) were created earlier in life
· the existing synapse pathways were thicker and stronger earlier in life
· the brain network or sub-networks have formed to operate more efficiently (i.e. less resources are needed to perform similar tasks)
· redundant or compensatory network pathways have been created
· networks are able to more flexibly adapt to the disruption caused by ageing and/or illness
· the brain naturally reorganises itself as we age and there may be more and less effective ways that this occurs
· that there may be some critical network threshold below which behavioural symptoms escalate dramatically
The most likely cause is some combination of all of the above factors. In addition, the brain may employ different strategies for various regions of the brain. For example, the brain networks that control conscious body movement, emotions and long term strategy planning might have different network structures for managing both function and reserve.
What are the Effects of Cognitive Reserve ?
There are also a number of hypothesis that scientists are exploring as to the effects of cognitive reserve :
· When dementia is diagnosed in individuals with more cognitive reserve, more pathology will exist but the symptoms of the disease should emerge much later. Therefore the overall prevalence of dementia should be much lower in individuals with higher cognitive reserve.
· When dementia is diagnosed in individuals with more cognitive reserve, the high incidence of pathology might cause a greater rate of decline at that time. However in this case quality of life should be greater for an extended period and where dementia is the cause of death we might reasonably expect that life duration could also be longer.
· The concept of cognitive reserve is applicable to a wide range of behavioural conditions and different brain functions that impact on people at varying ages. Individual differences exist in brain sub-networks and cognitive processes. These affect underlying task performance in a way that allows some people to cope better than others with normal cognitive decline or pathology. Therefore there will be individual differences in the amount of pathology required for the initial expression of different behavioural symptoms.
There is strong indication that a particular set of life activities are associated with a reduced risk of developing dementia and with a slower rate of memory decline in normal ageing. These include having a higher education, mentally stimulating occupations, strong social networks and having a variety of leisure interests. The amount of cognitive reserve appears to be plastic and influenced by aspects of experience in every stage of life. The scientific intent is that studies of cognitive reserve should point in the direction of successful interventions that will be preventative for the incidence of dementia and delay or maybe even reverse the behavioural effects of normal ageing. The goal is to identify and positively influence cognitive reserve factors.
How can we Build Cognitive Reserves ?
Unfortunately at this stage scientists cannot be definitive. We don’t know what is more beneficial - learning a new musical instrument, travelling in foreign countries, or changing careers in mid life. The benefits to our brains are likely to vary considerably between individuals. However, we are confident that pursuing new interests is better than continuing to do the same things all your life. And we assume that doing lots of different activities with ever challenging levels of complexity is better than doing just one or two. The more variety the better.
Novelty provides new challenges to the brain, causing brain networks to expand contributing to our mental wellbeing. The benefits of novelty should be actively pursued. We cannot just rely on the routine of everyday life. Different activities have independent but synergistic contributions, which means the more things you do and the earlier you start the better. And because our brains remain plastic throughout life you can always do something, it’s better late than never. Regardless of our age, the greater our level of involvement the more cumulative the effect.
In time, the cycle of clinical trials will give us greater understanding of the parameters of cognitive reserve. Right now, the most we can say is that the evidence of people having the least risk of developing dementia is pointing to those who have and continue to lead mentally stimulating lives, in their education, occupation and leisure activities.
What We Should Be Doing
Cognitive reserve acts as a savings account for the functionality of our brain if we invest in it. It builds up a resistance to both the normal mental decline we all experience as we age and potentially also protects us against degenerative brain illnesses such as Alzheimer’s disease. By actively engaging our brains in lots of novel activities and maintaining our social connections over our lifespan we preserve strong neural networks in our brain and help to protect against dementia. The amount of cognitive reserve we have is adaptable and is influenced by all the stimulating experiences we have in our lives. It’s never too late to start adding to this reserve capacity. It reinforces what doctors and researchers have been advising us for years - "use it or lose it". This is an investment we all need to make.
Much of the material on this webpage is derived from the published work of Yaakov Stern, PhD and his team of scientists at the Cognitive Neuroscience Division, Columbia University Medical Centre, USA who are leaders in cognitive reserve research. More information can be found at ....
Neuroscientist Yaakov Stern http://www.cumc.columbia.edu/dept/sergievsky/cnd/stern.html
Scientific Publication on Cognitive Reserve http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2739591/
A Savings Account for Your Brain
Cognitive reserve can be thought of as a savings account for the functionality of our brain. It is the ability to build up a resistance to mental decline and disease. The effect is similar to how physically fit people are more resilient against the common illnesses that unhealthy people generally seem to catch more often. The idea is that the stronger the neural networks in our brain the more reserve capacity there is to deal with the normal cognitive decline that we all experience with ageing and to help protect us against dementia. This reinforces what doctors and researchers have been advising us for years - "use it or lose it".
The concept of cognitive reserve has been around for more than 20 years, when it was first formally observed in a large number of autopsies. They revealed a significant amount of Alzheimer’s disease in the brains of some people who showed no signs of dementia behaviour when they died. More recently the evidence of behavioural mental tests compared to brain scan images supports the concept of cognitive reserve. It demonstrates that there are some circumstances where people can still actively participate in life seemingly unaffected by the death of large numbers of brain cells.
Cognitive reserve is the general term used to describe this capacity. However scientists don’t as yet know the exact mechanism that underlies it. They are still working to define both the parameters that affect it and the biological process itself. But they have established a number of concepts that are broadly agreed even if the underlying elements are still being debated and tested.