primary aging: The universal and irreversible physical changes that occur in all living creatures as they grow older. Primary aging is inevitable, programmed for each species.

compression of morbidity: A shortening of the time a person spends ill or infirm before dying, accomplished by postponing illness.

ageism: A prejudice whereby people are categorized and judged by their chronological age.

maximum life span: The oldest possible age that members of a species can live under ideal circumstances. For humans, that age seems to be 122 years.

genetic clock: A mechanism in the DNA of cells that regulates the aging process by triggering hormonal changes and cellular death and repair.

average life expectancy: The number of years the average person in a particular population group is likely to live.

secondary aging: The specific physical illnesses or conditions that become more common with aging but are caused by health habits and other influences that vary from person to person.

telomeres: The area of the tips of each chromosome that is reduced a tiny amount as time passes. By the end of life, the telomeres are very short.

wear and tear: A view of aging as a process by which the human body wears out because of the passage of time and exposure to environmental stressors.

calorie restriction: The practice of limiting dietary energy intake (while consuming sufficient quantities of vitamins, minerals, and other important nutrients) in hopes of slowing down the aging process.

universal design: The creation of settings and equipment that can be used by everyone, whether or not they are able-bodied and sensory-acute.

demographic shift: A shift in the proportions of the populations of various ages.

Hayflick limit: The number of times a human cell is capable of dividing. The limit for most human cells is approximately 50 divisions, an indication that the life span is limited by our genetic program.

elderspeak: A condescending way of speaking to older adults that resembles baby talk, with simple and short sentences, exaggerated emphasis, repetition, and a slower rate and a higher pitch than used in normal speech.

cellular aging: The ways in which molecules and cells are affected by age. Many theories aim to explain how and why aging causes cells to deteriorate.

life review: An examination of one’s own role in the history of human life, engaged in by many elderly people. This can be written or oral.

neurocognitive disorder (NCD): Any of a number of brain diseases that affects a person’s ability to remember, analyze, plan, or interact with other people.

tangles: Twisted masses of threads made of a protein called tau within the neurons of the brain.

osteoporosis: Fragile bones that result from primary aging, which makes bones more porous, especially if a person is at genetic risk.

Lewy body disease: A form of major NCD characterized by an increase in particular abnormal cells in the brain. Symptoms include visual hallucinations, momentary loss of attention, falling, and fainting.

vascular disease: Formerly called vascular or multi-infarct dementia, vascular disease is characterized by progressive loss of intellectual functioning caused by repeated infarcts (strokes), or temporary obstructions of blood vessels.

frontotemporal NCDs: Brain disorders that occur with serious impairment of the frontal lobes. (Also called frontotemporal lobar degeneration.)

self-actualization: The final stage in Maslow’s hierarchy of needs, characterized by aesthetic, creative, philosophical, and spiritual understanding.

Alzheimer’s disease (AD): The most common cause of major NCD, characterized by gradual deterioration of memory and personality and marked by the formation of plaques of beta-amyloid protein and tangles of tau in the brain.

Parkinson’s disease: A chronic, progressive disease that is characterized by muscle tremor and rigidity and sometimes major NCD; caused by reduced dopamine production in the brain.

ecological validity: The idea that cognition should be measured in natural settings and schedules.

control processes: The part of the information-processing system that regulates the analysis and flow of information. Memory and retrieval strategies, selective attention, and rules or strategies for problem solving are all control processes.

polypharmacy: Refers to a situation in which people take many medications. The various side effects and interactions of those medications can result in NCD symptoms.

major neurocognitive disorder (major NCD): Irreversible loss of intellectual functioning caused by organic brain damage or disease. Formerly called dementia, major NCD becomes more common with age, but it is abnormal and pathological even in the very old.

plaques: Clumps of a protein called beta-amyloid, found in brain tissues surrounding the neurons.