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Cognitive decline refers to a measurable reduction in one or more cognitive abilities — such as memory, attention, executive function, language, learning, judgment, and processing speed — from an individual’s previous level of functioning. Some degree of decline, particularly in processing speed and fluid abilities, is a normal feature of healthy aging and is referred to as age-related cognitive decline. When decline exceeds what is expected for a person’s age and education but does not interfere with independent daily functioning, it is classified as mild cognitive impairment (MCI) or, in DSM-5 terminology, mild neurocognitive disorder; when it is severe enough to interfere with independence in everyday activities, it is classified as major neurocognitive disorder (dementia). Cognitive decline can arise from a wide range of causes, including neurodegenerative disease, vascular and metabolic conditions, medication effects, and modifiable lifestyle and dietary factors.
Author and reviewer
Editorial responsibilityReferences and further reading
- Dominguez LJ, et al. Prevention of cognitive decline and dementia: Current evidence on lifestyle factors and dietary patterns. 2026. PMID: 42376437. View source
- Townsend RF, et al. Whole Dietary Patterns, Cognitive Decline and Cognitive Disorders: A Systematic Review of Prospective and Intervention Studies. Nutrients. 2023;15(2):333. DOI: 10.3390/nu15020333. PMID: 36678204. View source
How to cite this entry
Encyclopedia of Nutritional Psychology. (2026). Cognitive Decline. The Center for Nutritional Psychology.
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