cognitive decline
reduction in one or more cognitive abilities, such as memory, awareness, judgment, and mental acuity, across the adult lifespan. The presence and degree of decline varies with the cognitive ability being measured: Fluid abilities often show greater declines than crystallized abilities (see Cattell–Horn theory of intelligence). Cognitive decline is a part of normal healthy aging, but a severe decline is not normative and could be symptomatic of disease: It is the primary symptom of disease-induced dementias, such as Alzheimer’s disease.