What is Cognitive Reserve, Actually?

Post by Anastasia Sares

The takeaway

Cognitive function tends to decline as we age normally or when we are faced with diseases like Alzheimer’s. Cognitive reserve is a form of resilience that allows people to maintain good cognitive functioning—or at least to slow cognitive decline—even as aging and illness progress.

The idea of cognitive reserve

Studies of aging have noted large individual differences in rates of cognitive decline, whether it be in healthy aging or dementias like Alzheimer’s. Cognitive reserve is a concept scientists have proposed to account for this variability. Things like education and occupational complexity may contribute to cognitive reserve, with one study finding that high cognitive reserve reduced the risk of dementia by around 50%. However, to move the research forward, researchers need to first agree on how to define cognitive reserve. Over the past several years there has been an effort to do just that. In this article, we will present the definitions of Stern and colleagues, who are leaders in this field.

Three necessary elements

To show evidence of cognitive reserve at work, you need three elements. First, you need some kind of outcome measure: for example, the presence or absence of an Alzheimer’s diagnosis, or a score on a cognitive test. Second, you need some kind of risk factor. Often, this is brain-related, like the number of accumulated protein plaques or the integrity of white matter in the brain. But the risk factor doesn’t have to be from the brain: for example, a person’s age is, by itself, a risk factor for Alzheimer’s. These first two elements (the outcome and the risk factor) are assumed to have a causal relationship. For example, more plaques in the brain should lead to a greater likelihood of an Alzheimer’s diagnosis.

The third element is where it gets interesting. This is a protective factor that we think might moderate the relationship between the first two elements. For example, perhaps people who have more education can maintain their cognitive functioning for longer and delay their Alzheimer’s diagnosis compared to people with the same number of plaques in their brain but less education. Or perhaps people who are more socially active score higher on cognitive tests for their age than people who are less socially active.

Related concepts

There are a couple of concepts related to cognitive reserve, but slightly different. To differentiate these terms, a hardware/software analogy is sometimes used. Cognitive reserve is the “software” that allows for maintained function despite deteriorating “hardware,” while brain reserve is the pre-existing advantages in the biological “hardware” itself. For example, in a study looking at white matter integrity changes with age, you might find that some individuals just have better white matter integrity, to begin with, before any aging or disease. This means it will take more damage to the white matter to start affecting cognition. The hardware/software analogy is imperfect, and the line between cognitive reserve and brain reserve is fuzzy. After all, cognitive processes are also based in biology.

Brain maintenance, on the other hand, involves stalling the damage to the brain’s “hardware” so that the decline is not so sharp. For example, some people may accumulate white matter damage at a slower rate than others.

All of these elements are most informative when measured longitudinally (using multiple measurements over time), so long-term changes can be tracked. This would allow researchers to pick apart differences between cognitive reserve, brain reserve, and brain maintenance, where a single snapshot might not.

What’s the impact?

Cognitive resilience in the face of aging is increasingly important as populations all over the world grow older on average. Having a consensus on the definition of cognitive reserve allows scientists to move forward studying it, potentially identifying ways to build it up and increase quality of life in old age.

References +

Cabeza, R., Albert, M., Belleville, S., Craik, F. I. M., Duarte, A., Grady, C. L., Lindenberger, U., Nyberg, L., Park, D. C., Reuter-Lorenz, P. A., Rugg, M. D., Steffener, J., & Rajah, M. N. (2018). Maintenance, reserve and compensation: The cognitive neuroscience of healthy ageing. Nature Reviews Neuroscience, 19(11), 701–710. https://doi.org/10.1038/s41583-018-0068-2

Stern, Y., Albert, M., Barnes, C. A., Cabeza, R., Pascual-Leone, A., & Rapp, P. R. (2023). A framework for concepts of reserve and resilience in aging. Neurobiology of Aging, 124, 100–103. https://doi.org/10.1016/j.neurobiolaging.2022.10.015

Stern, Y., Arenaza‐Urquijo, E. M., Bartrés‐Faz, D., Belleville, S., Cantilon, M., Chetelat, G., Ewers, M., Franzmeier, N., Kempermann, G., Kremen, W. S., Okonkwo, O., Scarmeas, N., Soldan, A., Udeh‐Momoh, C., Valenzuela, M., Vemuri, P., Vuoksimaa, E., & and the Reserve, Resilience and Protective Factors PIA Empirical Definitions and Conceptual Frameworks Workgroup. (2020). Whitepaper: Defining and investigating cognitive reserve, brain reserve, and brain maintenance. Alzheimer’s & Dementia, 16(9), 1305–1311. https://doi.org/10.1016/j.jalz.2018.07.219

Nelson, M. E., Jester, D. J., Petkus, A. J., & Andel, R. (2021). Cognitive Reserve, Alzheimer’s Neuropathology, and Risk of Dementia: A Systematic Review and Meta-Analysis. Neuropsychology Review, 31(2), 233–250. https://doi.org/10.1007/s11065-021-09478-4