AGING

Aging is the accumulation of changes in an organism or object over time. Aging in humans refers to a multidimensional process of physical, psychological, and social change. 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. Research shows that even late in life potential exists for physical, mental, and social growth and development. Aging 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. Roughly 100,000 people worldwide die each day of age-related causes.

The term “aging” is somewhat ambiguous. Distinctions may be made between “universal aging” (age changes that all people share) and “probabilistic aging” (age changes that may happen to some, but not all people as they grow older, such as the onset of type two diabetes). Chronological aging, referring to how old a person is, is arguably the most straightforward definition of aging and may be distinguished from “social aging” (society’s expectations of how people should act as they grow older) and “biological aging” (an organism’s physical state as it ages). There is also a distinction between “proximal aging” (age-based effects that come about because of factors in the recent past) and “distal aging” (age-based differences that can be traced back to a cause early in person’s life, such as childhood poliomyelitis).

Differences are sometimes made between populations of elderly people. Divisions are sometimes made between the young old (65–74), the middle old (75–84) and the oldest old (85+). However, problematic in this is that chronological age does not correlate perfectly with functional age, i.e. two people may be of the same age, but differ in their mental and physical capacities. Each nation, government and non-government organization has different ways of classifying age.

Population aging is 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. Aging has a significant impact on society. 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. Thus, the aged have comparatively more political influence.

SUCCESSFUL AGING

The concept of successful aging can be traced back to the 1950s, and popularized in the 1980s. Previous research into aging 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.

Successful aging consists of three components:

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 aging than those that strictly meet these criteria.

Successful aging may be viewed an interdisciplinary concept, spanning both psychology and sociology, where it is seen as the transaction between society and individuals across the life span with specific focus on the later years of life. The terms “healthy aging” “optimal aging” have been proposed as alternatives to successful aging.

Six suggested dimensions of successful aging include:

1. No physical disability over the age of 75 as rated by a physician;
2. Good subjective health assessment (i.e. good self-ratings of one’s health);
3. Length of un-disabled life;
4. Good mental health;
5. Objective social support;
6. Self-rated life satisfaction in eight domains, namely marriage, income-related work, children, friendship and social contacts, hobbies, community service activities, religion and recreation/sports.

PREVENTION AND REVERSAL OF AGING

Several drugs and food supplements have been shown to retard or reverse the biological effects of ageing in animal models; none has yet been proved in humans.

Resveratrol, a chemical found in red grapes, has been shown to extend the lifespan of yeast by 60%, worms and flies by 30% and one species of fish by almost 60%. Small doses of heavy water increase fruit-fly lifespan by 30%, but large doses are toxic to complex organisms.

In 2002 a team led by Professor Bruce Ames at UC Berkeley discovered that feeding aged rats a combination of acetyl-L-carnitine and alpha-lipoic acid (both substances are already approved for human use and sold in health food stores) produced a rejuvenating effect. Ames said, “With these two supplements together, these old rats got up and did the macarena. The brain looks better, they are full of energy – everything we looked at looks like a young animal.” UC Berkeley has patented the use of these supplements in combination and a company, Juvenon, has been established to market the treatment.

In 2007 researchers at the Salk Institute for Biological Studies, identified a critical gene in nematode worms that specifically links eating fewer calories with living longer. Professor Andrew Dillin and colleagues showed that the gene pha-4 regulates the longevity response to calorie restriction. In the same year Dr Howard Chang of the Stanford University School of Medicine was able to rejuvenate the skin of two-year-old mice to resemble that of newborns by blocking the activity of the gene NF-kappa-B.

In 2008, a team at the Spanish National Cancer Research Center genetically engineered mice to produce ten times the normal level of the enzyme telomerase. The mice lived 26% longer than normal. The same year a team led by Professor Michael O Thorner at the University of Virginia discovered that the drug MK-677 restored 20% of muscle mass lost due to ageing in humans aged 60 to 81. The subjects’ growth hormone and insulin-like growth factor 1 (IGF-1) levels increased to that typical of healthy young adults.

In 2009 a drug called rapamycin, discovered in the 1970s in the soil of Easter Island in the South Pacific, was found to extend the life expectancy of 20-month-old mice by up to 38%. Rapamycin is generally used to suppress the immune system and prevent the rejection of transplanted organs. Dr Arian Richardson of the Barshop Institute said, “I never thought we would find an anti-ageing pill in my lifetime; however, rapamycin shows a great deal of promise to do just that.” Professor Randy Strong of the University of Texas Health Science Center at San Antonio said, “We believe this is the first convincing evidence that the ageing process can be slowed and lifespan can be extended by a drug therapy starting at an advanced age.”

Also in 2009 the British Journal of Nutrition reported a study at Tufts University in Boston which showed that brain function and motor skills in aged rats could be improved by adding walnuts to their diet. The human equivalent would be to eat seven to nine walnuts per day.

In September the same year researchers at UC Berkeley discovered they could restore youthful repair capability to muscle tissue taken from men aged 68 to 74 by in vitro treatment with mitogen-activated protein kinase. This protein was found to be essential for the production of the stem cells necessary to repair muscle after exercise and is present at reduced levels in aged individuals.