This Alzheimer's and public health glossary describes terms and concepts related to dementia, brain health, and the public health response.

Alzheimer's Disease

An irreversible, progressive brain disorder that develops across a continuum and slowly destroys memory and thinking skills and, eventually, the ability to carry out the simplest tasks. Symptoms usually develop slowly and get worse over time, becoming severe enough to interfere with daily tasks.

Brain Health

A concept that involves making the most of the brain's capacity and helping to reduce some risks that occur with aging. Brain health refers to the ability to draw on the strengths of the brain to remember, learn, play, concentrate, and maintain a clear, active mind.


Spouses, partners, adult children, other relatives, and friends providing unpaid help to people living with dementia who may need help with everyday activities. Caregivers often assist with diverse activities of daily living such as:
  • Personal care.
  • Household management.
  • Medication and health care management.
  • Coordination of financial matters.
For more information on terms related to caregiving, please see the Caregiving Glossary.


The mental functions involved in attention, thinking, understanding, learning, remembering, solving problems and making decisions. Cognition is a fundamental aspect of an individual's ability to engage in activities, accomplish goals, and successfully negotiate the world. It can be viewed along a continuum — from optimal functioning to mild cognitive impairment to dementia.

Cognitive Impairment

Trouble with:
  • Remembering.
  • Learning new things.
  • Concentrating.
  • Making decisions that affect everyday life.


The loss of cognitive functioning — thinking, remembering, and reasoning — and behavioral abilities to such an extent that it interferes with a person's daily life and activities. These functions include memory, language skills, visual perception, problem solving, self-management, and the ability to focus and pay attention. Alzheimer's is the most common cause of dementia. Other types include vascular dementia, dementia with Lewy bodies and frontotemporal dementia.

Early Detection and Diagnosis 

Identifying cognitive issues as early as possible. The earlier dementia is diagnosed, the sooner people and their families can receive information, care and support. A formal diagnosis allows people to have access to available treatments and interventions, build a care team, participate in support services, and potentially enroll in clinical trials. 

Mild Cognitive Impairment (MCI)

A slight but measurable decline in cognitive abilities that includes memory and thinking. A person living with MCI is at increased risk of developing dementia.

Risk Reduction

Preventing or delaying the onset of cognitive decline or dementia. Growing evidence shows that modifying certain risk factors,  especially hypertension, and promoting healthy behaviors, particularly heart healthy behaviors, can reduce the risk of developing cognitive decline and may also reduce the risk of dementia. 

Subjective Cognitive Decline (SCD)

Self-reported difficulties with thinking or memory that happen more often or get worse. People experiencing SCD are at increased risk of later developing dementia.