Terminology Related to Neurodegenerative Disorders & Cognitive Decline:

Age-related cognitive decline (ARCD): Deterioration in cognitive performance that can be a normal part of aging. It is also sometimes referred to as cognitive aging.

Mild cognitive impairment (MCI): Cognitive impairment that has reached a level of deterioration from normal cognitive function identifiable by individuals, family members, or clinicians, but without significant functional impairment in daily activities (i.e., individuals may have mild functional impairments but can adapt to them).

Clinical Alzheimer’s-type dementia (CATD): Cognitive impairment severe enough that an individual can no longer function independently. This impairment may be due to Alzheimer’s disease (i.e., the abnormal build-up of amyloid and tau proteins in the brain) or to “mixed” causes of dementia, such as Alzheimer’s disease combined with alpha-synuclein or TDP-43 proteins or with vascular disease in the brain. This term is not widely used in the field; the committee uses it here to reflect the increasing recognition of mixed dementia, which may be difficult to differentiate in a clinical setting.

Clinical Alzheimer’s-type dementia (CATD) is common and costly, affecting approximately 4 to 5 million adults in the United States at an annual estimated cost of more than $200 billion. An even greater number of older Americans have mild cognitive impairment (MCI) without dementia. Public health experts warn that the burden associated with Alzheimer’s disease could nearly triple by 2050 as the number of adults over age 65 grows, increasing annual costs to more than $1 trillion in the United States. Globally in 2015, 46.8 million people were living with dementia, costing an estimated $818 billion that year. In addition to CATD and MCI, cognitive changes in older adults, or age-related cognitive decline (ARCD), often occur as a typical part of aging.