Gerontology (from the Greek γέρων, geron , "old man" and -λογία, logy , "study of" ; coined by
Ilya Ilyich Mechnikov in 1903) is the study of the social, psychological and biological aspects of aging.
Gerontology is the study of the aging processes and individuals as they grow from middle age through later life.
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Gerontologists define aging as follows: a c ontinuous, u niversal, p rogressive, i ntrinsic, and d eleterious ( CUPID ) process that decreases a organism's ability to maintain homeostasis in the face of environmental stressors and therefore increases the organism's likelihood of dying .
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Gerontology encompasses the following:
1. Studying physical, mental, and social changes in people as they age
2. Investigating the aging(ageing), process itself ( biogerontology )
3. Investigating the interface of normal ageing and age-related disease
( geroscience )

4.Investigating the effects of an ageing population on society
5. Applying this knowledge to policies and programs, including the macroscopic (for example government planning) and microscopic (for example running a nursing home) perspectives.

It includes researchers and practitioners in the fields of biology;
1.medicine,
2. nursing,
3. dentistry,
4. social work,
5. physical and occupational therapy,
6.psychology & psychiatry,
7. sociology, economics, political science, architecture, pharmacy, public health, housing and anthropology.

Gerontologists view aging in terms of four distinct processes :
1. Chronological aging,
2. Biological aging,
3. Psychological aging, and
4. Social aging.

1. Chronological aging is the definition of aging based on a person's years lived from birth.
2. Biological aging refers to the physical changes that reduce the efficiency of organ systems.
3. Psychological aging includes the changes that occur in sensory and perceptual processes, cognitive abilities, adaptive capacity, and personality.
4. Social aging refers to an individual's changing roles and relationships with family, friends, and other informal supports, productive roles and within organizations.

It to refer specifically to the medical study of diseases and problems of the elderly. (the comprehensive health care of older persons and the well-being of their informal caregiver )
It has been identified as a physical therapy specialization in order to acknowledge the advanced-level skills of physical therapists who seek to address the unique medical functional problems of older persons.

Life expectancy : is how long, on average, an organism can be expected to Live.
Longevity is the period of time an organism is expected to live under ideal circumstances.
The maximum recorded lifespan for humans, reported in 2010, was 122.5 years for females and 116 years for males.
Lifespan : is the length of life for an organism.
For instance, if you live to age 99, that would be your lifespan.

The biological changes are slow-moving and can vary within one's own species, arbitrary dates are usually set to mark periods of life.
The human divisions given below are not valid in all cultures:
Juvenile [via infancy , childhood , preadolescence , adolescence (teenager)]: 0–19
Early adulthood : 20–39
Middle adulthood : 40–59
Late adulthood : 60+

Ages can also be divided into decades:
Term
Denarian
Vicenarian
Tricenarian
Quadragenarian
Quinquagenarian
Sexagenarian
Septuagenarian
Octogenarian
Nonagenarian
Centenarian
Supercentenarian
Age (years, inclusive)
10 to 19
20 to 29
30 to 39
40 to 49
50 to 59
60 to 69
70 to 79
80 to 89
90 to 99
100 to 109
110 and older

The term "aging" refers to the biological process of growing older in a deleterious sense, what some authors call "senescence" ( Williams,
1957 ; Comfort, 1964 ; Finch, 1990 ).
Ageing, in its broadest sense is the continuous and irreversible decline in the efficiency of various physiological processes once the reproductive phase of life is over.

Definition of normal Ageing
Ageing, the process of growing old, is defined as the gradual biological impairment of normal function, probably as a result of changes made to cells (mitotic cells, such as fibroblasts and post-mitotic cells, such as neurons) and structural components (such as bone and muscle).

These changes would consequently have a direct impact on
• the functional ability of organs (such as the heart, kidney and lungs),
• biological systems (such as the nervous, digestive and reproductive system) and
• ultimately the organism as a whole.

The following is a description setting out five criteria ’ s for ageing, as proposed by Strehler (1962).
Cumulative: Effects of ageing increase with time.
Universal: All members of a species display signs of ageing.
Progressive: Ageing is a series of gradual changes.
Intrinsic: Changes would take place even in a “ perfect ” environment.
Deleterious: Changes which occur compromise normal biological functions.

Most developed world countries have accepted the chronological age of 65 years as a definition of 'elderly' or older person.
The UN agreed cutoff is 60+ years to refer to the older population.
The age of 60 or 65, roughly equivalent to retirement ages in most developed countries, is said to be the beginning of old age.

How well we age depends on many factors
The functional capacity of an individual's biological system increases during the first years of life, reaches its peak in early adulthood and naturally declines thereafter.
The rate of decline is determined, at least in part, by our behaviours and exposures across the whole life course.

These include what we eat, how physically active we are and our exposure to health risks such as those caused by smoking, harmful consumption of alcohol, or exposure to toxic substances.

SPECIAL ATTRIBUTES OF THE
GERIATRIC PATIENT
Geriatric medicine is based in the principle that elderly persons are different from young and middle-aged adults. The following are some of the important clinical differences:
1. Physiologic reserve is diminished.
2. Homeostasis is more easily disrupted and more difficult to reestablish.

3. Disease in one organ system may present with symptoms in another, weaker organ system. For example, the stress of infection or anemia may present as heart failure if there is marginal cardiac compensation.
4. Disease may present in an altered form, either in an atypical fashion or with nonspecific symptoms
(e.g., delirium, falls, urinary incontinence, sleep disturbance, weight loss).

5. Polypharmacy (multiple drug use) may mask symptoms or produce new symptoms.
6. Drug effects are more pronounced due to changes in both pharmacokinetics (handling of drugs) and pharmacodynamics (action of drugs).
7. Biologic variability is greater than in younger patients.
8. Multiple medical, psychological, and social problems may coexist and interact.

patterns of health decline and increased disease with old age called morbidity.
For example, do health problems start around the same age in all people and expand over extra years of life for the long-lived, or are the problems delayed, occurring closer to the end of life among exceptional agers?

Demographic Measurements of Aging - Aging has been defined as the collection of changes that render human beings progressively more likely to die ( Medawar, 1952 ). Indeed, one hallmark of aging in humans and in many other species is an agerelated increase in mortality rates shortly after maturity

Death by underlying or multiple cause, expressed in rates per
100,000 people, as a function of age for the 2001 US population aged 85 and older. Source: National Center for Health
Statistics , Data Warehouse on Trends in Health and Aging .

Death by underlying or multiple cause, expressed in rates per 100,000 people or in percentage of the total deaths, for the 2001 US population in two age groups: 45-54 years and 85 years of age and older. Source: National Center for Health
Statistics , Data Warehouse on Trends in Health and Aging .
45-54 years
Cause of death
Diseases of the heart
Malignant neoplasm
Cerebrovascular diseases
Parkinson's disease
Alzheimer's disease
Pneumonia
Chronic lower respiratory diseases
Diabetes mellitus
Certain infectious and parasitic diseases
Atherosclerosis
Others
Over 85 years
Incidence
% of deaths
92.8
Incidence
21.66% 5607.5
% of deaths
37.48%
126.3 29.48% 1747 11.68%
15.1
0.1
0.2
4.6
3.52%
0.02%
0.05%
1.07%
1485.2
1312.8
703.2
676.5
9.93%
8.77%
4.70%
4.52%
8.5 1.98% 638.2 4.27%
13.6
22.9
0.5
143.8
3.17%
5.35%
318.6
243.8
0.12% 177.3
33.57% 2050.9
2.13%
1.63%
1.19%
13.71%