Information about Ageing

Ageing or aging is any change in an organism over time. Aging refers to a multidimensional process of physical, psychological, and social change (Hultsch and Deutsch). Some dimensions of aging grow and expand over time, while others decline. Reaction time, for example, may slow with age, while knowledge of world events and wisdom may expand (Schaie). Research shows that even late in life potential exists for physical, mental, and social growth and development. This article focuses on the social, cognitive, cultural, and economic effects of ageing. The biology of ageing is treated in detail in senescence. Ageing is an important part of all human societies reflecting the biological changes that occur, but also reflecting cultural and societal conventions. Age is usually measured in full years — and months for young children. A person's birthday is often an important event.

Population aging refers to the increase in the number and proportion of older people in society. Population aging has three possible causes: migration, longer life expectancy (decreased death rate), and decreased birth rate. The societal effects of age are great. Young people tend to commit most crimes, they are more likely to push for political and social change, to develop and adopt new technologies, and to need education. Older people have different requirements from society and government as opposed to young people, and frequently differing values as well. Older people are also far more likely to vote, and in many countries the young are forbidden from voting, and thus the aged have comparatively more political influence.

Senescence

Main article: Senescence

In biology, senescence is the state or process of ageing. Cellular senescence is a phenomenon where isolated cells demonstrate a limited ability to divide in culture (the "Hayflick Limit," discovered by Leonard Hayflick in 1965), while Organismal senescence is the ageing of organisms.



Ageing is believed to have evolved because of the increasingly smaller probability of an organism still being alive at older age, due to predation and accidents, both of which may be random and age-invariant. It is thought that strategies which result in a higher reproductive rate at a young age, but shorter overall lifespan, result in a higher lifetime reproductive success and are therefore favoured by natural selection. Essentially, ageing is therefore the result of investing resources in reproduction, rather than maintenance of the body (the "Disposable Soma" theory).

Organismal ageing is generally characterized by the declining ability to respond to stress, increasing homeostatic imbalance and increased risk of disease. Because of this, death is the ultimate consequence of ageing. Not all organisms age, presumably due to different selective pressures during evolution. Organisms that are suspected not to age include certain fish (e.g., Sturgeon), plants, and hydra.

Some researchers are treating ageing as a "disease" in gerontology (specifically biogerontologists). That is, as genes that have an effect on ageing are discovered, ageing is increasingly being regarded in a similar fashion to other genetic conditions; potentially "treatable." As an example of genes known to affect the ageing process, the sirtuin family of genes have been shown to have a significant effect on the lifespan of yeast and nematodes. Numerous other examples exist of genes that affect lifespan including RAS1 and RAS2 (yeast genes, although a human homologue exists). Over-expression of RAS2 increases lifespan in yeast substantially.

In addition to genetic ties to lifespan, diet has been shown to substantially affect lifespan in many animals. Specifically, caloric restriction (that is, restricting calories to 30-50% less than an ad libitum animal would consume, while still maintaining proper nutrient intake), has been shown to increase lifespan in mice up to 50%. Caloric restriction works on many other species beyond mice (including species as diverse as yeast and Drosophila), and appears (though the data is not conclusive) to increase lifespan in primates according to a study done on Rhesus monkeys at the National Institute of Health (US).



Drug companies are currently searching for ways to mimic the lifespan-extending effects of caloric restriction without having to severely reduce food consumption, and with respect to cellular senescence, it has been shown that individual cells can be immortalized by the introduction of an additional gene for telomerase.

Dividing the lifespan

A human life is often divided into various ages. Because biological changes are slow moving and vary from person to person, arbitrary dates are usually set to mark periods of human life. In some cultures the divisions given below are quite varied.

In the USA, adulthood legally begins at the age of eighteen or nineteen, while old age is considered to begin at the age of legal retirement (approximately 65).

• Pre-conception: Ovum, Spermatozoon, Pre-existence
• Conception: Fertilization
• Pre-birth: Conception to birth
• Infancy: Birth to 2
• Childhood: 2 to 12
• Adolescence: 13 to 20
• Early Adulthood: 21 to 34
• Middle Adulthood: 35 to 54
• Late Adulthood: 55+
• Death
• Post-Death: Decomposition, Cryonics, (Afterlife, Ghost)

Ages can also be divided by decade:

• Denarian: someone between 10 and 19 years of age
• Vicenarian: someone between 20 and 29 years of age
• Tricenarian: someone between 30 and 39 years of age
• Quadragenarian: someone between 40 and 49 years of age
• Quinquagenarian: someone between 50 and 59 years of age
• Sexagenarian: someone between 60 and 69 years of age
• Septuagenarian: someone between 70 and 79 years of age
• Octogenarian: someone between 80 and 89 years of age
• Nonagenarian: someone between 90 and 99 years of age
• Centenarian: someone between 100 and 109 years of age
• Supercentenarian: someone over 110 years of age

See also Seven ages of man for an older system of dividing the human life.

Cultural variations

In some cultures (for example Serbian and Russian) there are two ways to express age: by counting years with or without including current year. For example, it could be said about the same person that he is twenty years old or that he is in twenty-first year of his life.

Considerable numbers of cultures have less of a problem with age compared with what has been described above, and it is seen as an important status to reach stages in life, rather than defined numerical ages. Advanced age is given more respect and status.

Traditional Chinese culture use different ageing method, called Xusui (虛歲) with respect to common ageing which called Zhousui (周歲). In the Xusui method, people are born at age 1, not age 0. See also East Asian age reckoning for more information.

Society

Legal

There are variations in many countries as to what age a person legally becomes an adult.

Most legal systems define a specific age for when an individual is allowed or obliged to do something. These ages include voting age, drinking age, age of consent, age of majority, age of criminal responsibility, marriageable age, age where one can hold public office, and mandatory retirement age. Admission to a movie for instance, may depend on age according to a motion picture rating system. A bus fare might be discounted for the young or old.

Similarly in many countries in jurisprudence, the defence of infancy is a form of defence by which a defendant argues that, at the time a law was broken, they were not liable for their actions, and thus should not be held liable for a crime. Many courts recognize that defendants, which are considered to be juveniles, may avoid criminal prosecution on account of their age.

Economics and marketing

The economics of ageing are also of great import. Children and teenagers have little money of their own, but most of it is available for buying consumer goods. They also have considerable impact on how their parents spend money.

Young adults are an even more valuable cohort. They often have jobs with few responsibilities such as a mortgage or children. They do not yet have set buying habits and are more open to new products.

The young are thus the central target of marketers.^[1] Television is programmed to attract the 15 to 35 years olds. Movies are also built around appealing to the young.

Health care demand

Many societies in the rich world, i.e. Western Europe and Japan, have ageing populations. While the effects on society are complex, there is a concern about the impact on health care demand. Saltman et al. (2006) argue that the large number of suggestions in the literature for specific interventions to cope with the expected increase in demand for long-term care in ageing societies can be organized under four headings: improve system performance; redesign service delivery; support informal caregivers; and shift demographic parameters.

Cognitive effects

Steady decline in many cognitive processes are seen across the lifespan, starting in one's thirties. Research has focused in particular on memory and ageing, and has found decline in many types of memory with ageing, but not in semantic memory or general knowledge such as vocabulary definitions, which typically increases or remains steady.

Societal impact

Societal ageing refers to the demographic ageing of populations and societies.^[2] Cultural differences in attitudes to ageing have been studied.^[3]

Emotional improvement

Given the physical and cognitive declines seen in ageing, a surprising finding is that emotional experience improves with age. Older adults are better at regulating their emotions and experience negative affect less frequently than younger adults and show a positivity effect in their attention and memory. The emotional improvements show up in longitudinal studies as well as in cross-sectional studies, and so cannot be entirely due to only the happier individuals surviving.

Terminology

The concept of successful ageing can be traced back to the 1950s, and popularised in the 1980s. Previous research into ageing exaggerated the extent to which health disabilities, such as diabetes or osteoporosis, could be attributed exclusively to age, and research in gerontology exaggerated the homogeneity of samples of elderly people.^[4][5]

Successful ageing consists of three components:^[6]

1. Low probability of disease or disability;
2. High cognitive and physical function capacity;
3. Active engagement with life.

A greater number of people self-report successful ageing than those that strictly meet these criteria.^[4]

Healthy ageing has been proposed as a more appropriate term.^[4]

Optimal ageing better takes into account how many elderly people suffer some health detriments, the cultural diversity in approaches to death and how, in Western Europe and Northern America, people may approach death may differ from approaches taken in other cultures.^[7]

Theories

Modernization Theory: This is the view that the status of the elderly has declined since industrialization and the spread of technology.

Disengagement Theory: This is the idea that separation of older people from active roles in society is normal and appropriate, and benefits both society and older individuals.

Activity Theory: A view holding that the more active people are, the more likely they are to be satisfied with life.

Continuity Theory: The view that in aging people are inclined to maintain, as much as they can, the same habits, personalities, and styles of life that they have developed in earlier years.

Cognitive Theory: A view of aging that emphasizes individual subjective perception, rather than actual objective change itself, as the factor that determines behavior associated with advanced age.

Demographic Transition Theory: The idea that population aging can be explained by a decline in both birthrates and death rates following industrialization.

Exchange Theory: The idea that interaction in social groups is based on the reciprocal balancing of rewards depending on actions performed

Political Economy Theory: A societal perspective on the aging process that explains that the status and resources of the elderly, as well as how people age, are shaped by each person's place in the social structure and the economic and political forces that impact their sociopolitical location.

Biological theories

Reproductive-Cell Cycle Theory: The idea that aging is regulated by reproductive hormones that act in an antagonistic pleiotrophic manner via cell cycle signaling, promoting growth and development early in life in order to achieve reproduction, but later in life, in a futile attempt to maintain reproduction, become dysregulated and drive senescence (dyosis).

Wear-and-Tear theory: The idea that changes associated with aging are the result of chance damage that accumulates over time.

Somatic Mutation Theory: This is the biological theory that aging results from damage to the genetic integrity of the body’s cells.

Error Accumulation Theory: This is the idea that aging results from chance events that gradually damage the genetic code.

Accumulative-Waste Theory: The biological theory of aging that points to a buildup of cells of waste products that presumably interferes with metabolism.

Autoimmune Theory: This is the idea that aging results from gradual decline in the body’s immune system.

Aging-Clock Theory: The idea that aging results from a preprogrammed sequence, as in a clock, built into the operation of the nervous or endocrine system of the body.

Cross-Linkage Theory: This is the idea that aging results from accumulation of cross-linked compounds that interfere with normal cell function.

Free-Radical Theory: The idea that free radicals (unstable and highly reactive organic molecules) create damage that gives rise to symptoms we recognize as aging.

Cellular Theory: This is the view that aging can be explained largely by changes in structure and function taking place in the cells of an organism.

Measure of age

The normal point of time from where to measure the age of a human being is from birth. However, this is not how gynaecologists measure age in prenatal development. Rather, age for people not yet born is normally measured in gestational age, taking the last menstruation of the woman as a point of beginning. Alternatively, fertilization age, beginning from fertilization can be taken.

See also

• Adultism
• Aging brain
• Aging Research Centre
• Biodemography
• Biological immortality
• Life expectancy
• List of life extension-related topics
• Longevity
• Maturity (psychological)
• Memory and aging
• Orthomolecular medicine
• Population ageing
• Retirement
• Senescence
• The Grim Reaper Gene
• Youth bulge

Notes

References

• Aldwin, C.M. & Gilmer, D.F. (2004). Health, Illness and Optimal Ageing. London: Sage. ISBN 0-7619-2259-8
• Bass, S.A. (2006). Gerontological Theory: The Search for the Holy Grail. The Gerontologist, 46, 139-144.
• Charles, S.T., Reynolds, C.A., & Gatz, M. (2001). Age-related differences and change in positive and negative affect over 23 years. Journal of Personality and Social Psychology, 80, 136-151.
• Mather, M., & Carstensen, L. L. (2005). Aging and motivated cognition: The positivity effect in attention and memory. Trends in Cognitive Sciences 9, 496-502. PDF
• Masoro E.J. & Austad S.N.. (eds.): Handbook of the Biology of Aging, Sixth Edition. Academic Press. San Diego, CA, USA, 2006. ISBN 0-12-088387-2
• Rowe, J.D. & Kahn, R.L. (1987). Human ageing: Usual and successful. Science, 237, 143-149
• Rowe, J.D. & Kahn, R.L.(1997). Successful ageing. The Gerontologist, 37 (4) 433-40
• Strawbridge, W.J., Wallhagen, M.I. & Cohen, R.D. (2002). Successful ageing and well-being: Self-rated compared with Rowe and Kahn. The Gerontologist, 42, (6)
• Zacks, R.T., Hasher, L., & Li, K.Z.H. (2000). Human memory. In F.I.M. Craik & T.A. Salthouse (Eds.), The Handbook of Aging and Cognition (pp. 293-357). Mahwah, NJ: Erlbaum.
• Saltman, R.B., Dubois, H.F.W. and Chawla, M. (2006) The impact of aging on long-term care in Europe and some potential policy responses, International Journal of Health Services, 36(4): 719-746.
• Thesaurus of Aging Terminology (5,1MB, 272p), 8th edition (2005), AARP

Moody, Harry R. Aging: Concepts and Controversies. 5th ed. California: Pine Forge Press, 2006.

External links

• The arrow of time - a photo-essay of a family ageing, with yearly portraits over 30 years
• Brain Health Roadmap by CDC and Alzheimer's Association - an article on their joint initiative

•  • [ e] Human development: biological - psychological
Stages	Infancy • Childhood • Adolescence • Adulthood - Early adulthood • Middle adulthood • Late adulthood
Development	Child development • Youth development • Ageing & Senescence
Theorists-theories	John Bowlby-attachment • Jean Piaget-cognitive • Lawrence Kohlberg-moral • Sigmund Freud-psychosexual • Erik Erikson-psychosocial