Types of aging (primary, secondary and tertiary)
Aging has been defined as the biological process by which the body changes throughout development, especially as adulthood advances. In general, aging is related to a structural degradation which in turn implies losses in capacities functional, with special emphasis on adaptation and self-care.
Currently there is no consensus in the scientific community about the specific nature and definition of aging. However, we can distinguish three types of aging: primary, secondary and tertiary or . Each of these types encompasses different changes and is determined by specific causes.
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Types of aging
The main types of aging are the following.
1. Primary aging
When we talk about primary aging, we are referring to a series of progressive and unavoidable changes that occur in all people as the years go by. Like the other types of aging, it implies a deterioration in the general functioning and in the ability to adapt to the environment.
All non-pathological processes that occur as a result of age are classified as primary aging; for this reason it is also called "normative aging". It occurs throughout the adult life, although its effects are much more noticeable in advanced ages, especially in people who do not enjoy good health.
Among the changes that make up this type of aging are menopause, hair thinning and graying, the decline in the speed of cognitive processing, the loss of strength, the progressive appearance of sensory deficits or the deterioration of the sexual response.
The biological processes involved in primary aging alter physical functioning, but are also associated with psychological and social changes. The latter are influenced to a greater extent by the context, although when talking about interindividual variability this type of aging overlaps with the secondary one.
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Causes of primary aging
The main theories about primary aging conceptualize it as a preprogrammed process at the genetic level . Factors such as the limited capacity of cell regeneration and the progressive deterioration of the immune system play a key role in this type of aging.
The theory of genetic programming states that with maturity genes that trigger aging are activated, and the pacemaker proposes that these changes are due to the hormonal imbalance produced by the "disconnection" of the biological clock of the hypothalamus. According to the immunological theory, in advanced ages the immune system happens to attack the body.
Other perspectives argue that primary aging is a consequence of the accumulation of damage in the body, and not of unmodifiable genetic factors. These hypotheses, which in general have less acceptance than genetic ones, are known as "non-genetic cell theories" or "random damage theories".
The theory of the free radical, the most popular in this group, states that the liberation of free electrons that results from the normal activity of the organism causes cumulative damage to cell membranes and chromosomes .
Other nearby hypotheses attribute the deterioration to the spontaneous construction of harmful molecules, to the inability of the body to protect itself indefinitely from harmful environmental influences, to the accumulation of errors in the synthesis of proteins (which would alter genetic transcription) or to the normal effects of metabolism.
2. Secondary aging
This type of aging consists of changes caused by behavioral and environmental factors , alien to natural biological processes. It is often said that secondary aging is one that can be prevented, avoided or reversed, but this is not always the case; the key feature is the non-universality of the processes that comprise it.
The main factors that determine the intensity of secondary aging are the state of health, the lifestyle and environmental influences. Thus, suffering from diseases such as cardiovascular disorders, eating an unhealthy diet, being sedentary, consuming tobacco, exposing oneself directly to the sun or breathing polluted air enhance this type of change.
Many physical and psychological deficits typical of old age can be considered a consequence of secondary aging even though they tend to be seen as manifestations of the primary; For example, pathological cognitive deterioration and cancer become much more frequent as age advances, but they do not occur in all people.
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3. Tertiary aging
The concept of tertiary aging refers to the rapid losses that occur shortly before death . Although it affects the organism at all levels, this type of aging is especially notable in the cognitive and psychological field; For example, in the last months or years of life the personality tends to destabilize.
In 1962 Kleemeier proposed the hypothesis of the "terminal fall", which in English is called "terminal drop". This author and some longitudinal investigations have suggested that, as death approaches, cognitive abilities and adaptive capacity deteriorate in a very marked way, which causes an increase in vulnerability.
The cascade aging model of Birren and Cunningham proposes that the three types of aging interact with each other, so that their effects are mutually reinforcing. Thus, secondary aging causes an intensification of the effects of natural biological deterioration, and these changes are even more marked at the end of life.