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Glossary of Gerontology Definitions

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  • Synopsis: Glossary of definitions and terms for Gerontology the study of social psychological and biological aspects of aging - Published: 2009-01-11 (Rev. 2015-01-23). For further information pertaining to this article contact: Ian Langtree at Disabled World.

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"Gerontology examines the biological, economic, psychological, social and health/fitness aspects of the aging process."

Glossary of definitions and terms for Gerontology,the study of the social, psychological and biological aspects of aging. It is distinguished from geriatrics, which is the branch of medicine that studies the disease of the elderly.

What is Gerontology

Gerontology is the study of the social, psychological and biological aspects of aging. It is distinguished from geriatrics, which is the branch of medicine that studies the disease of the elderly. Gerontology examines the biological, economic, psychological, social and health/fitness aspects of the aging process.

Also see our How Long Will I Live - Life Span Expectancy Chart showing average number of years you will live for according to which country you live in.

Gerontology Definitions and Terms

Aging: The life-long process of growing older; not just a later life experience

Alzheimer's Disease: The most common form of dementia. A degenerative disease that attacks the brain and results in impaired memory, thinking, and behavior.

Arthritis: A general term referring to disease of the joints. Arthritis includes over 100 different diseases, often involving aches and pains in the joints and connective tissues throughout the body. Most forms of arthritis are chronic, but proper treatment can frequently reduce symptoms substantially.

Apoptosis: Programmed Cell Death (PCD). This process gets rid of unneeded cells and is particularly important for "sculpting" tissue and organ structure during development of the embryo (or larval metamorphosis in insects), but may occur at any time even in adult cells when a tissue needs to be remodeled.

Average Life Expectancy: The age at which 50 percent of the members of a population have died, when plotted on a standard survival curve. This statistic is normally calculated from birth, but may be recomputed in terms of expected years remaining at any age.

Bases - These are molecules with one or two nitrogen containing ring structures. The biologically important bases are the purines Adenine and Guanine and the pyrimidines Cytidine, Thymine, and Uracil. DNA and RNA are composed of linked sequences of nucleotides.

Biomarker: A measurable parameter of physiological age that is a more useful predictor of remaining life expectancy than chronological age. The ability to measure biomarkers is extremely important in evaluating the efficacy of any potential life-extending intervention.

Blastocyst - A pre-implantation embryo that contains a fluid-filled cavity called a blastocoel.

Caloric Restriction (CR) - A diet in which calorie intake is reduced, compared with ad libitum (eat as much as you like) diets, without any reduction in nutritional requirements (protein, water, vitamins, or minerals).

Cancer: A clonal growth (cells all descended from one ancestral cell) that undergo continuing mitotic divisions and are not inhibited in their growth when they come in contact with neighboring cells (contact inhibition).

Cataract: A cloudiness or opacity that develops in the lens of the eye and results in poorer vision. Previously one of the leading causes of blindness in persons over 60, cataracts can now be surgically removed.

Centenarian: A person who is 100 years or older. There were 2,300 centenarians identified in the 1980 U.S. census.

Chromosome: The structures in the nucleus of the cell, consisting of DNA bound to histones and other proteins. The genes are made of DNA (although the majority of the DNA sequence is not part of any gene). Genes are arranged along the chromosomes in a continuous sequence. Chromosome protein structure allows for selective activation (genes are transcribed into protein) or silencing (genes are not expressed), and thus for differential expression of the genome in different cell types and expression of genes in appropriate sequences during development of the organism or under various metabolic conditions.

Cleavage: The mitotic divisions of the early embryo that occur in the absence of growth to divide the embryo in to many smaller nucleated cells.

Cloning: The use of the chromosomes from an adult cell to create an identical twin (copy) of an organism by inserting the adult nucleus into an egg from which the nucleus has been removed, stimulating embryogenesis, and implanting the embryo into the uterus of a surrogate mother. Reproductive cloning of sheep, mice, goats, cows, pigs, and mules have been widely accomplished.

Cohort: A set of people born during a specific time period; also a set of people born during a historical era that creates different inter-cohort characteristics such as size, composition, experiences, and values.

Dementia: A syndrome characterized by a decline in intellectual functioning. May be caused by more than 70 diseases, the most common being Alzheimer's Disease.

Demography: The study of a population and those variables bringing about change in that population. Variables studied by demographers are age, sex, race, education, income, geographic trends, birth, and death.

Diploid Cell: A cell with pairs of homologous chromosomes.

DNA: An abbreviation for Desoxy Ribonucleic Acid. Double stranded DNA molecules consist of antiparallel (running in opposite directions) chains of nucleotides in which the sugar component is desoxyribose. The chains are arranged in a double helix with the two chains wrapped around each other and bound together so that each "A" is paired with a "T" (A:T pair) and each "G" is paired with a "C" (G:C pair). Thus, when the chains unwind and separate, new identical antiparallel sequences can be copied along their lengths. Thus, DNA is self-replicating.

Compression of Morbidity Hypothesis: Prof. James F. Fries, M.D., a rheumatologist at the Stanford University School of Medicine, established the "compression of morbidity" hypothesis in 1980. He suggested that if the onset of disability due to age-related diseases and conditions could be postponed to a greater degree than average life expectancy would increase, then total lifetime disability could be compressed into a shorter average period and the cumulative average lifetime disability would also be reduced.

Disposable Soma: From an evolutionary point of view, the Prime Directive of any organism is to transform available energy from the environment into the maximum number of progeny. Part of the energy is consumed in the maintenance of the organism's somatic (body) tissues (for growth and repair of injury) and part is used to propagate the germ-line tissues.

Egg: A female haploid germ cell.

Entropy: A measure of the level of disorder or randomness in a closed system. It can be thought of either in the sense of thermodynamic/metabolic processes or the increasing molecular disorder in a structure. It can be thought of as the same process by which erosion occurs when soil is exposed to rain and wind.

Evidence-Based Medicine: The practice of medicine with treatment recommendations that have their origin in objective tests of efficacy published in the scientific literature rather than anecdotal observations.

Fecundity: The ability to produce offspring. High fecundity means the ability to produce progeny rapidly and in large numbers. In the demography of human populations, fecundity is the physiological ability to reproduce, as opposed to fertility.

Fertility: Reproductive Potential. In demography, the number of births per year divided by the number of women of childbearing age, expressed as a rate.

Gene: a functional unit of heredity. It is a segment of DNA located at a specific site on a chromosome whose length is typically several thousand base pairs long. A gene directs the formation of an enzyme or other protein by means of processes of transcription and translation. More precisely, a gene is a sequence of DNA that can be activated and copied into messenger RNA (or mRNA) by the process known as transcription.

Generation: Though popularly used as a synonym for cohort, the term is also applied within the context of the family. Children form one generation, their parents another, their grandparents a third, and so on.

Geriatrics: The branch of medicine specializing in the health care and treatment of older persons. It is defined by the World Health Organization as the branch of medicine that is concerned with the health of older adults in all aspects: preventative, clinical, remedial, rehabilitative, and continuous surveillance.

Genotype: The genetic makeup of a cell, organism or group of organisms, with respect to a single trait or group of traits; the sum total of genes transmitted from parents to their offspring.

Genome: The complete collection of genes in the nucleus of each cell of our bodies. There are now known to be somewhat less than 25,000 genes in the human genome.

Geriatrics: A branch of Internal Medicine concerned with the care and treatment of older persons and the treatment and amelioration of diseases of old age and frailty.

Gerontology: The multidisciplinary study of all aspects of aging, including health, biological, sociological, economic, behavioral, and environmental.

Germ Cell - Either an egg or a sperm cell.

Gerontology: A branch of biology focusing on the common mechanisms of aging across all multicellular species. Gerontologists, for example, are keen to understand species that appear to exhibit very gradual or negligible senescence over a long time interval. In this context, gerontologists may study yeast, worms, fruit flies, mice, rock fish, tortoises, bats, parrots, humans, and other creatures exhibiting exceptional longevity.

Gerontome: The subset of the genome whose genes affect longevity, either significantly reducing or increasing the average lifespan of an organism.

Glaucoma: A disease in which pressure builds up within the eye and causes internal damage, gradually destroying vision. Often hereditary, glaucoma usually affects persons after 40. Symptoms may be blurred vision, difficulty in focusing, loss of peripheral vision, or slow adaptation to severe and irreversible loss of vision has occurred. While no method exists for preventing glaucoma, diagnosing the disease in its earliest stages can prevent further damage.

Gompertz Model: A class of statistical models first proposed by the nineteenth-century British actuary Benjamin Gompertz, in which the hazard rate for death rises exponentially with increasing age of the organism (at least after an initial period of high risk of mortality at birth and infancy and a much lower risk in late childhood and adolescence). Today, the Wibel Model is superior to the Gompertz Model, as it more accurately explains observed demographic data.

Grandparent: A role that an older person assumes when their children have children of their own.

Grand-parenting Hypothesis: This is the supposition that abruptly terminating reproduction at a particular age (menopause) and prolonged survival of human females after menopause may have been selected for because of better success in child-rearing (and hence survival of the gene pool) when older women focus their resources on the welfare of their grandchildren and thereby increase their likelihood of survival of the tribe, rather than investing energy in producing more and more children of their own, and potentially compromising the reproductive success of their more mature offspring.

Haploid Cell: A cell with half the normal compliment of chromosomes, typically a germ cell.

Hayflick Limit: The limit to the number of times a cell is can divide during serial cell culture. The value of this limit as a predictor of maximum lifespan of the organism is still unproven.

Homeostasis: The physiological capacity of an organism to regulate itself by rapidly restoring internal conditions following a sudden perturbation in the external environment.

Inner Cell Mass: Cells that give rise to the embryo proper and that arise from the inner cells of an early pre-implantation embryo.

Life History: The combination of age-specific survival probabilities and fertilities characteristic of a species; the time table of individual development and aging for a representative organism (e.g., in humans, from fertilization conception, to embryogenesis, implantation/placentation; organogenesis/fetogenesis, birth, infancy, adolescence, puberty, adulthood, menopause, loss of vitality, frailty/morbidity, and ultimately, death mortality.

Lifespan: The maximum lifespan of a species is the characteristic observed age of death for its very oldest individual(s) (e.g., for humans 122+ years). On the other hand, average lifespan is the age at which 50 percent of the members of a species or group has died. Over the last two centuries, average life expectancy has risen significantly, while maximum lifespan has hardly changed at all.

Life Cycle: (1) The entire course of a person's life, from infancy to old age. Health, social roles and expectations, and socioeconomic status tend to change as an individual develops. (2) The genetically prescribed course followed by all living organisms, including humans, from conception to death through stages of development and change.

Longevity: The condition or quality of being long lived.

Longevity Genes: Gerontic genes that extend or shorten the maximum lifespan of a species.

Meals-on-Wheels: A program that delivers meals to the homebound.

Medicare: A federal entitlement program of medical insurance for persons age 65 and over provided through the Social Security system. Covers mostly acute health care needs.

Menopause: The time of life when a woman ceases to menstruate and can no longer become pregnant, usually about age 45 to 50.

Multi-potent Cell: A stem cell that has limited capabilities for specialization, normally within a specific tissue type.

Mutation: Any change in DNA structure which alters the established order of the bases. This may cause a gene (or series of genes) to fail to be activated normally (either to be silenced or, conversely, to be expressed inappropriately) or may cause a gene to express a protein with abnormal structure (and hence abnormal function).

Necrosis: Cell death secondary to traumatic injury. Necrosis invariably induces a subsequent inflammatory reaction, as distinguished from apoptosis which does not.

Nucleotides: molecules which consist of a purine or pyrimidine base, a ribose or desoxyribose sugar, and a phosphate group.

Osteoporosis: A decrease in density of the bones causing structural weakness throughout the skeleton. Fractures can result from even a minor injury or fall. Some bone loss occurs normally in older adults, but osteoporosis develops most often in white women after menopause.

Parthenogenesis - The development of an individual from an egg without fertilization.

Phenotype: The external manifestations of gene expression whether at the level of the cell (e.g., muscle cells are long and thin and contain contractile fibrils; nerve cells have excitable membranes and communicating processes) or the organism (e.g., the giraffe has a long neck; a leopard, spots, and elephants, trunks).

Pluripotent Cell: A cell capable of giving rise to most tissues of an organism.

Progeria: A human disease or syndrome in which some characteristics of senescence are accelerated so that relatively young individuals appear prematurely aged. Examples include Hutchinson Guilford Syndrome (HGS is a rare autosomal-dominant disorder with a classic withered presentation leading to an early death in the teenage years.

Protein: A linear sequence of Amino Acids whose three-dimensional shape determines a particular function in the body.

Proteome: The collection of all proteins in the body of an organism. For humans, it is estimated that there are 250,000 - 300,000 proteins, of which fewer than half have been cataloged thus far.

Retirement: Period or life stage following termination of and withdrawal from a regular job and from income from employment. Difficult to delimit because some older persons retire from one job and take another full or part-time job.

Reproductive Cloning: The creation of an embryo using SCNT with the aim of creating a new (identical twin) individual of that species.

Reprogenic: Techniques at the intersection of reproductive medicine and genetics for manipulating gametes and embryos.

RNA: Ribonucleic acid. RNA is a sequential chain of the nucleotides Adenosine, Guanosine, Thymidine, and Uridine. In RNA, the sugar molecules are ribose. RNA is typically single stranded. The sequence of most RNA molecules is copied from specific DNA sequences by enzymes in a process called transcription.

Senescence: That portion of aging that begins at older ages, after one passes the point of minimum mortality, around age 12 for humans. More specifically, senescence is not a single disease. It is characterized as a generic, increased susceptibility to a myriad of age-related chronic diseases and a reduced ability to repair damage.

Social Security: A national insurance program that provides income to workers when they retire or are disabled and to dependent survivors when a worker dies. Retirement payments are based on workers' earnings during employment.

Somatic Cell: A diploid cell of the body; a cell other than a germ cell (an egg or a sperm).

Somatic Cell Nuclear Transfer (SCNT): The transfer of a cell nucleus from a somatic cell into an enucleated egg (one from which the nucleus has been removed).

Sperm: A male haploid germ cell.

Stem Cell: An undifferentiated cell that possesses the ability to divide for indefinite periods in culture and may give rise to highly specialized cells of each tissue type. There are embryonic stem cells found in the blastocyst that are known to be totipotent, while adult stem cells found in bone marrow, for example, may only be pluripotent (not able to produce an entire new organism but are able to produce all three tissue types).

Survival Function: The probability that an individual will remain alive at a particular age. The percentage of an experimental cohort that remains alive over the course of the experiment.

Telomere/Telomerase: Repetitive DNA sequences at the four ends of the chromosome, which can be lengthened by an RNA-containing enzyme called telomerase.

Therapeutic Cloning: The creation of a several day-old embryo using SCNT with the aim of harvesting the cells for subsequent tissue-culture amplification and injection into a host for therapeutic purposes (presumably without fear of GVH [Graft vs. Host] Disease or immunological rejection).

Totipotent Cell: A cell having an unlimited capability to create a new organism. A totipotent cell has the capacity to specialize into an embryo, extra-embryonic membranes and tissues, and all post-embryonic tissues and organs.

Translational Research: Clinical investigation with human subjects (patients or normal volunteers) in which knowledge obtained from basic research with genes, cells, or animals is translated into diagnostic or therapeutic interventions that can be applied to the treatment or prevention of disease or frailty.

Trophobastic Cells: Cells that contribute to the placenta but not to the embryo itself and which are required for an embryo to implant into the uterine wall.


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