What is the aging of the body?
What is aging?
By 2050, one-third of the French population will be over 60. Medicine, science, and nutrition have evolved over the centuries, particularly in the last century, leading to a considerable increase in life expectancy at birth. An aging population leads to new problems, both individual and public health-related. What changes occur in an aging human body? Which functions are affected? Can these changes be prevented? What treatments are available for the different functions that decline?
In this thematic dossier and in the associated articles, we will attempt to answer these questions.
Definition of aging
The generally accepted definition of aging is as follows:
“Aging encompasses all the physiological and psychological processes that modify the structure and functions of the organism from middle age onwards. It is the result of the intertwined effects of genetic factors (intrinsic aging) and environmental factors to which the organism is subjected throughout its life. It is a natural and physiological process affecting all living beings and must be distinguished from the effects of diseases.”
Life expectancy, what are we talking about? A simple concept, but not so simple...
To put it simply: life expectancy is the amount of time remaining to live at a given moment...
We often talk about life expectancy at birth, but this is a concept that changes over time. Indeed, the longer you are alive, the greater your chances of staying alive... Life expectancy increases as time goes by. For example, in 2021, life expectancy at birth was 79.4 years for a man, but it was still 19.2 years for a 65-year-old man: 19 + 65 = 84 years, which is almost 5 years more than life expectancy at birth.
This is explained by the fact that by the age of 65, one has “managed to survive (or avoid)” all the events since birth that could have led to death…
So, the older you get, the more life expectancy increases 🤯: The life expectancy of a 90-year-old man is 4 years and 2 months. That's 94 years (94 > 84 > 79 years...).
Furthermore, life expectancy at birth is also changing. Currently, as the years go by, life expectancy at birth increases. INED (the French National Institute for Demographic Studies) allows us to see the evolution of life expectancy over time. In 1800, it was approximately 32 years for a man; by 1900, it had significantly increased to 45 years; 70 years in 1980; and 79 years today.
Life expectancy at birth is largely influenced by our lifestyle: advances in medicine, nutrition, and the end of major wars all condition this life expectancy.
For those interested, there are formulas that allow us to assess the contribution of each age group to life expectancy. One such formula is the Pressat index, which estimates the contribution of each age group to life expectancy over a two-year period.
What are the consequences of increased life expectancy?
They are relatively simple. The first consequence observed in France is demographic. There is an aging population with an age pyramid that is shifting in favor of older people.
The second consequence is the emergence of "new" pathologies linked to aging. Indeed, the more elderly individuals there are, the more likely we are to observe age-related pathologies. The older we get, the greater our risk of being affected by pathologies related to the decline in bodily functions.
What happens when we get old?
Aging is accompanied by, or leads to, a decline in the body's capabilities. This reduces its ability to adapt, particularly to stressful situations. The impact of aging varies from one organ to another, and also from one individual to another.
Aging and metabolism
Body composition changes with age. Simply put, lean mass decreases while fat mass increases, resulting in more fat and less muscle. Furthermore, not only does muscle mass decrease, but muscle composition also changes: the proportion of type II (fast-twitch) fibers decreases while type I (slow-twitch) fibers increase. This contributes to changes in carbohydrate metabolism and leads to a decreased tolerance to high carbohydrate intake.
Aging and the nervous system
The description of the nervous system and its alterations is far too vast and complex to be included in this article. However, it is important to know that the nervous system undergoes changes during aging. More specifically, there is a decrease in the number of neurons (particularly cortical neurons) accompanied by changes in the amount of neurotransmitters.
Motor and sensory abilities are little altered, but cognitive performance declines with age.
The decline in cognitive performance is accompanied, among other things, by a decrease in the quantity and quality of sleep (at least partly due to the reduction in the ability of the pineal gland to secrete melatonin), and a decrease in the perception of thirst (changes in the sensitivity of osmoreceptors and the arginine vasopressin system).
Aging and meaning
Aging affects the sense organs and impairs hearing, vision, but also taste and smell.
Aging and the cardiovascular and respiratory systems
Among the consequences of aging on the cardiovascular system are a decrease in maximum heart rate, an increase in heart mass, and a thickening of its walls, which reduces cardiac performance. Blood vessels also tend to stiffen, leading to an increase in blood pressure.
The respiratory system also loses performance. All of these changes lead to a decrease in adaptability to exertion.
Aging and the musculoskeletal system
An aging of the muscular system is observed (decrease in the proportion of type II fibers, decrease in muscle mass, decrease in contraction force) which is accompanied by an aging of the skeleton (decrease in bone mass → osteoporosis) and of the joints (decrease and wear of cartilage, decrease in flexion range of motion).
Aging of the urinary tract
The urinary system is affected by aging, leading to a decrease in the kidney's filtration capacity. However, it appears that urinary aging is not a constant process and does not affect all individuals.
Aging and the digestive system
In addition to the aging and wear of teeth, which must be preserved to maintain a good quality diet, the digestive system also loses efficiency with age.
- Decreased salivary flow
- Decrease in acid secretions
- Increased transit time
- Decreased pancreatic and liver function
These performance declines lead to slower digestion, a reduced ability of the body to adapt to nutrient loads (especially carbohydrate loads) and also result in lipid balance abnormalities.
Skin aging
The skin thins, loses elasticity, the number of melanocytes decreases, and wrinkles appear. The growth rate of nails and hair slows with age, and the decrease in melanocytes leads to hair depigmentation.
A decrease in the effectiveness of the sebaceous glands is observed, leading to dry skin.
Aging and the immune system
The immune system loses performance with age. Cell-mediated immune responses (particularly those involving T lymphocytes) decrease.
What are the mechanisms that cause aging?
Several factors contribute to the aging process. Aging is a normal and inevitable phenomenon. While we all experience aging, it does not affect everyone equally.
Research on the phenomena related to aging is very important, but we are already able to explain a good part of the phenomena that lead to the various losses of performance and function.
Aging is a complex, multifactorial phenomenon that inevitably affects all individuals.
Heredity, genetic factors
Living a long life is partly a family affair... It has been observed that an individual's genetic makeup influences their ability to live a long and healthy life. This phenomenon has been observed in twins, and it seems that certain genotypes predispose individuals to a longer lifespan; thus, it appears that life expectancy is partly hereditary.
Alongside hereditary factors, there are also acquired genetic factors. Throughout life, genetic material (DNA) is subjected to damage, resulting in lesions and alterations. The body is adapted to these damages and is capable of repairing DNA, up to a certain point. Over time, repair errors accumulate, leading to losses of efficiency, function, or even cancer.
For example, mitochondrial DNA* more easily accumulates errors in its DNA, leading to an alteration of mitochondrial function.
* The mitochondrion is an organelle, present in cells and responsible for “energy production”. The mitochondrion, whose probable origin is the inclusion of a bacterium in our cells (endosymbiosis theory), possesses its own genetic material.
Furthermore, it has been shown that cell renewal is limited (Hayflick's law) and at least partly determined by the length of our telomeres**.
** Telomeres are repetitive DNA sequences located at the ends of chromosomes. They do not contain genes and serve to protect the integrity of the genetic material. With each cell division, telomeres are shortened. Once telomeres are worn out, cells enter senescence.
Environmental factors influence aging
Environmental exposure to pollutants or mutagens (notably alcohol and tobacco) leads to alterations in DNA, fatty acids, and proteins, resulting in cellular dysfunction. These dysfunctions are numerous and can lead to both loss of function and cancer.
Free radicals, reactive oxygen species naturally produced by the body's normal functions, are capable of damaging DNA and various cellular components. The body is adapted and possesses defense systems such as:
- Glutathione
- Antioxidant vitamins (A, E, C)
- The Catalases
- Superoxide dismutase
But little by little the effectiveness of the control systems decreases and the production of free radicals increases, causing damage, leading to a loss of effectiveness and a vicious circle.
How to fight against aging or how to age better?
It is possible to limit or slow down the effects of aging. Most of the levers for action are lifestyle and dietary measures:
- Ensure you have a balanced diet rich in fruits and vegetables. Note that as we age, it's important to maintain adequate protein intake to preserve muscle mass. Amino acid and protein intake is subject to splanchnic segregation, which limits their bioavailability. Nutritional strategies exist to overcome this segregation, such as citrulline consumption. It's possible to adapt your diet to prioritize beneficial foods, for example, those that support normal vision .
- Combating oxidative stress requires ensuring an optimal intake of antioxidants. The best advice, once again, is to maintain a balanced diet. Supplements, particularly glutathione, can be used to supplement this intake. However, excessive antioxidants should be avoided as they can have negative effects. Excessive beta-carotene consumption should also be avoided by smokers.
- Engage in regular physical activity: the goal here is to have a suitable level of physical activity that will help maintain muscle mass, bone mass, and mobility. Remember that any unused function tends to decline... ;)
- Finally, there are other drug-based or experimental approaches that will not be discussed here.
Focus on eye aging
The eyes are responsible for vision, a sense that must be preserved to maintain independence and quality of life. In addition to the well-known eye strain , the eyes are subject to several age-related effects. There are vision problems such as myopia, hyperopia, and astigmatism that are inherent to the age of aging. As we age, the eye also suffers from presbyopia, a condition caused by a loss of elasticity in the lens. As the lens stiffens, it loses its ability to focus the image; at certain distances, vision becomes blurry, and corrective lenses become necessary.
While presbyopia is universal, other conditions affect the aging eye, such as:
Focus on osteoarticular aging
The skeleton and joints are subject to aging. Osteoarticular aging can have a significant impact on quality of life because it leads to skeletal fragility on the one hand, and pain and decreased joint mobility on the other.
We have dedicated a series of articles to aging:
- of the skeleton, and more specifically osteoporosis and its treatments
- joints and more specifically osteoarthritis and associated treatments .
Aging and Phytocea?
At Phytocea , we are committed to the optimal functioning of the body, maintaining quality of life, and preserving independence. We have developed several supplements designed to support the aging body. Among these, our flagship supplement is O.Retine , intended, among other things, to maintain optimal vision.
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O.Retina
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