Before the development of more advanced neuroimaging techniques, a definitive diagnosis of dementia could only be made after the death of the patient, when an autopsy revealed characteristic changes in the brain.
These have revealed abnormalities in protein shapes that are characteristic of Alzheimer’s disease or other types of dementia. Surprisingly, as early as the 1960s, researchers noticed that some elderly people who showed no signs of cognitive decline during their lifetime had brain changes characteristic of dementia after death [1]. This prompted research into the importance of cognitive fitness for maintaining good mental abilities in old age, despite injury or disease.
How does our brain change over the years?
Like all organs in the body, the brain changes as we age. One of the main changes is a reduction in the volume of brain tissue, which includes a reduction in the number of synapses, or connections between nerve cells. In addition, the levels of chemical transmitters that influence mental and emotional processes decline and the vascular system becomes less functional, which can also reduce blood supply to the brain. These changes make the brain more vulnerable to disease processes.
The consequences of an ageing brain are reflected in its function: we process information more slowly, it is harder to maintain attention, working memory is reduced and it is sometimes harder to find the right words. These changes are a normal part of ageing that most people experience.
Research shows that the first disease processes associated with dementia start to develop 10 to 20 years before the first symptoms appear.
Normal ageing or dementia?
While the changes described above are a normal part of ageing, some individuals develop pathological changes that lead to severe cognitive decline or dementia. The most common cause of dementia is Alzheimer’s disease (AD), which is characterised by the accumulation of amyloid plaques, neurofibrillary tangles from the tau protein, and neurodegeneration of the brain. Research shows that the first disease processes start to develop 10 to 20 years before the first symptoms appear, often as early as middle age [2].
The secret of some of the "oldest old"
Surprisingly, some individuals retain good mental abilities well into old age, despite developing the disease processes characteristic of dementia. These individuals, often aged 90 years or more, show remarkable mental vitality, even though post-mortem examinations of their brains reveal signs of Alzheimer’s pathology, such as amyloid plaques and neurofibrillary tangles.
Although these changes should theoretically lead to dementia, these individuals never develop dementia. Their stories are the subject of long-term research that follows the individuals over decades. The first results of such studies reveal that cognitive preservation is not a matter of chance, but the result of a complex combination of factors, including genetics, lifestyle and mechanisms that experts explain by the concept of cognitive resilience.
Some people do not develop dementia, even though they have the brain changes characteristic of Alzheimer's disease. This is due to cognitive resilience, which helps the brain to adapt and compensate for the effects of the disease.
Cognitive resilience: the key to understanding
It is cognitive resilience that is the key to. cognitive resilience) offers a scientific explanation for the ability of individuals to maintain good mental abilities despite disease-related changes in the brain. This resilience is manifested by the brain using alternative neural pathways to adapt and compensate for the impact of the disease. Recent research shows that individuals with high cognitive resilience often have more newly formed neural outgrowths, which allow the formation of new neural connections and thus better brain plasticity [3].
How to increase cognitive resilience?
Although there is no cure for dementia, a healthy lifestyle can reduce the risk of cognitive decline by almost half.
Prevention is the key
Just as there is no cure for the common cold, there is currently no cure for dementia. However, a healthy lifestyle and preventive measures can reduce the risk of cognitive decline. Recent studies show that addressing modifiable risk factors could reduce the risk of dementia by almost half [4]. These include everything from controlling chronic health conditions and alcohol abuse to diet, sleep and addressing visual and hearing impairment.
Text by POMNI Institute
Citations:
[1] Blessed, G., Tomlinson, B. E., & Roth, M. (1968). The association between quantitative measures of dementia and of senile change in the cerebral grey matter of elderly subjects. The British journal of psychiatry : the journal of mental science, 114(512), 797-811. https://doi.org/10.1192/bjp.114.512.797
[2] Bateman, R. J., Xiong, C., Benzinger, T. L., Fagan, A. M., Goate, A., Fox, N. C., Marcus, D. S., Cairns, N. J., Xie, X., Blazey, T. M., Holtzman, D. M., Santacruz, A., Buckles, V., Oliver, A., Moulder, K., Aisen, P. S., Ghetti, B., Klunk, W. E., McDade, E., Martins, R. N., … Dominantly Inherited Alzheimer Network (2012). Clinical and biomarker changes in dominantly inherited Alzheimer’s disease. The New England journal of medicine, 367(9), 795-804. https://doi.org/10.1056/NEJMoa1202753
[3] Guptarak, J., Scaduto, P., Tumurbaatar, B., Zhang, W. R., Jupiter, D., Taglialatela, G., & Fracassi, A. (2024). Cognitive integrity in Non-Demented Individuals with Alzheimer’s Neuropathology is associated with preservation and remodeling of dendritic spines. Alzheimer’s & dementia : the journal of the Alzheimer’s Association, 20(7), 4677-4691. https://doi.org/10.1002/alz.13900
[4] Livingston, G., Huntley, J., Liu, K. Y., Costafreda, S. G., Selbæk, G., Alladi, S., … & Mukadam, N. (2024). Dementia prevention, intervention, and care: 2024 report of the Lancet standing Commission. The Lancet, 404(10452), 572-628.
