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Cognitive Aging
Cognitive Aging and Dementia
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What happens to our thinking abilities as we age?

As part of aging, people often experience changes in thinking abilities, or cognitive functions. Cognitive aging is classified across 3 categories based on severity: normal cognitive aging, mild cognitive impairment (MCI), or dementia.

Sushi Science | Janelle Letzen | Aging
Normal Cognitive Aging
Unhealthy Cognitive Aging

Most adults experience normal cognitive aging without ever reaching MCI/dementia severity. Common changes are in speed of thinking, memory for new info, and language. For example, it might take someone longer to think of answers to questions, remember where he/she put his/her keys 30 minutes ago, or find the word that is right on the tip of his/her tongue. These changes are mild and do not get in the way of a person’s daily routine.


For those who develop MCI/dementia, brain changes start in the “preclinical” stage. E.g., someone who develops Alzheimer’s disease will start developing plaques/tangles. However, it might be years until the person actually experiences cognitive changes.


MCI is the stage between normal cognitive aging and dementia. This is when preclinical brain changes advance enough to produce cognitive impairments. These impairments, though, are still not bad enough to affect tasks like driving or cooking. Some people with MCI never progress to dementia severity and possibly improve. 


Although “dementia” and “Alzheimer’s disease” are often used interchangeably, “dementia” is actually an umbrella term for communicating how far cognitive changes have progressed. These patients’ symptoms are severe enough to question whether he/she can handle finances, cook, drive, etc., without someone’s help. Specific terms like “Lewy body dementia” and “Alzheimer’s disease” refer to the suspected cause of cognitive changes, like buildup of “alpha-synuclein” or plaques/tangles in the brain, respectively. Although these conditions have different pathophysiology and symptoms, both are considered “dementia” when symptoms are severe enough.


[1] Harada, C. N., Love, M. C. N., & Triebel, K. L. (2013). Normal cognitive aging. Clinics in geriatric medicine, 29(4), 737-752.

[2] Sperling, R. A., Aisen, P. S., Beckett, L. A., Bennett, D. A., Craft, S., Fagan, A. M., ... & Park, D. C. (2011). Toward defining the preclinical stages of Alzheimer’s disease: Recommendations from the National Institute on Aging-Alzheimer's Association workgroups on diagnostic guidelines for Alzheimer's disease. Alzheimer's & dementia, 7(3), 280-292.

[3] Roberts, R., & Knopman, D. S. (2013). Classification and epidemiology of MCI. Clinics in geriatric medicine, 29(4), 753-772.

[4] “What is Lewy Body Dementia?” National Institute on Aging

[5] “Alzheimer’s Disease Fact Sheet” National Institute on Aging

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