Immunologic theory of aging. It views aging as a consequence of an evolutionarily programmed process of "immunological decline" that occurs with age. The efficiency of immunity peaks during adolescence. The ability to resist infections, destroy harmful microbes, identify mutated cells, and respond to vaccines, decreases over the which makes the body vulnerable to the negative joint action of external and internal factors, leading to disease and death. One of the key aspects underlying immunologic aging is the immunosenescence[7] age-related changes in the thymus gland responsible for training immune cells[8].
AGING AS A RESULT OF DAMAGE (ERRORS) ACCUMULATION
While supporters of "programmed aging" theories view age-adverse changes as the result of an inevitable evolutionary program, followers of "damage theory" do not consider aging a "genetic doom." They believe that the body accumulates many "breakdowns" with age due to the influence of external factors, stress, etc. A gradual accumulation of such damages leads to the development of age-related diseases and, eventually, to death.
There are examples of damage accumulation theories.
DNA damage theory. During cell division and copying of DNA molecules, there is always a risk of genetic errors (mutations) that accumulate with age and result in age-related diseases, primarily malignant tumors. In addition, adverse mutations, accumulating with age, can occur under the influence of factors external to the cell: ultraviolet radiation, virus entry, inserting their genome into hereditary material, etc.[9].
Genetic instability theory. It is not about mutations associated with damage, but rather about various changes in the genome occurring in the chromosome division. For example, such things as aneuploidy, the presence of an abnormal number of chromosomes in a cell, are identified in the fetal brain at all stages of intrauterine development. After birth, the number of such neurons decreases significantly, but some of them remain and can cause brain cancer[10].
Free radical theory. Supporters of this theory affirm that free radicals (particles, containing oxygen with one missing electron) are the cause of cellular malfunction. They are needed for many biochemical processes and are constantly formed in the body during breathing. By leaving the place where they needed, they sort of "take" an electron from the body, and this is called an oxidative reaction. Free radicals are a serious threat to cell activity because they damage proteins and lipids[11].
Among the numerous theories of aging today, the following concepts are also emphasized.
Apoptosis theory. Body tissues are constantly updated: "worn-out" cells whose function is deteriorating, as well as cells damaged by infection, having genetic mutations, regularly commit "suicide." Programmed cellular self-destruction is called apoptosis. In Greek, ἀπόπτωσις means "leaf fall": old cells die, like autumn leaves, to make way for the younger generation. There is an apoptosis gene in the DNA of each cell that triggers cellular self-destruction in response to molecular signals. The problem is that over the years, the sensitivity of cells to signals, activating their "suicide," decreases, leading to an accumulation of damaged, low-functioning cells. The aging process is based on the decreased ability of tissues to remove aged cells[12].
Elevational (ontogenetic) theory of aging. In the mid-twentieth century, the Soviet gerontologist V. M. Dilman related aging and ontogeny[13] (individual development) of the homeostatic systems of the organism. The scientist named an elevation in the hypothalamus sensitivity threshold the "conductor" of an endocrine system to homeostatic signals as the key mechanism of aging. In a series of experiments, it was proved that this mechanism is based on the adverse changes in the reproductive, hypothalamic-pituitary-adrenal axis, which provides the necessary number of glucocorticoids in the blood (the so-called stress hormones) and increases their secretion under stress, which eventually leads to hyperadaptosis, i.e., a condition of excessive body adaptation to stress. The same mechanism in the metabolic homeostasis system causes the accumulation of body fat, a decrease in tissue sensitivity to insulin, and the development of atherosclerosis. Dilman found that age-related transformations occurred because of homeostatic ontogenesis, creating conditions for the formation of malignancies. Thus, the scientist concluded that aging is not programmed, but is a byproduct of the genetic developmental program. This led to the belief that aging can be slowed down if homeostasis is stabilized at the level achieved by the end of the organism's development.
Telomere theory of aging. The number of divisions of each cell in the body is limited. This is because the protective structures at the ends of chromosomes, called telomeres, shorten with each cell division[14]. Telomere shortening may be a molecular "clock" triggering aging. It was found that the enzyme telomerase, which protects telomeres from shortening, is actively produced in cancer cells, that can divide almost infinitely. Telomerase activity has been detected in more than 85 % of malignant tumors, whereas it is absent in cells of healthy tissues[15].
Inflammatory theory of aging. This concept intersects with the immunologic theory of aging, but the priority here is given to the overblown immune response to various factors, including autoimmune responses "aggression" directed at one's tissues and not on the loss of the ability to fight off infections and recognize mutations. Under this theory, which is considered one of the most relevant today, aging is a general inflammatory process affecting all organs. It is inflammation that underlies the development of such age-related diseases as atherosclerosis, Alzheimer's disease, cardiovascular disease, diabetes mellitus type II[16].
We told only some theories of aging there are many more. This large number of views on the causes and nature of age-related changes demonstrates the lack of a unified understanding of the process. It also suggests that aging is based not on a single mechanism, affecting which could indefinitely prolong youth, but on a complex set of causes operating at the genetic, molecular, and evolutionary levels. The multifactorial nature of aging helps us to understand that prevention of aging shall also be comprehensive and diversified.
HEALTHY LIFESTYLE HELPS TO SLOW DOWN AGING
A healthy lifestyle has many definitions, but all scientists agree on one trend: it is a way of living aimed to maintain and improve health, both physical and mental. And firstly, people themselves are responsible for their well-being: they must have the knowledge and skills, as well as be active in achieving the goal of being healthy.
A healthy lifestyle is a combination of many healthy habits (and rejection of bad ones, such as smoking, drinking abuse, etc.). The effectiveness of some aspects of a healthy lifestyle to prevent aging has been confirmed by many studies.
1. PHYSICAL ACTIVITY. Exercise is seen as a beneficial stress for the body, positively affecting various aspects of physiology. It is proved that moderate stress caused by physical activity slows down the skeletal muscles aging[17], activates the antioxidant systems of the body[18], normalizes metabolic processes[19], stimulates the formation of somatotropic hormone (growth hormone), which significantly accelerates regeneration processes in the body[20], helps normalize blood pressure levels and reduces the risk of hypertonia[21].
FUN FACT
TO REDUCE THE RISK OF PREMATURE DEATH, IT IS ENOUGH TO JUST STAND MORE DURING THE DAY.
A study conducted by scientists from UCLA School of Medicine found that older people who spent more time standing had a 37 % lower risk of death compared to those who sat more often during the day. The longest "standing" time among the subjects was about 90 minutes a day, but it turned out that even half an hour spent in an upright stance allow achieving the desired effect.
2. BREATHING EXERCISES. Breathing is essential to the functions of the body. But do we breathe right? If we do not pay enough attention to this important process, and breathe frequently and intermittently, as it happens unknowingly, it causes dysfunction of the internal organs, and major health problems from insomnia to atherosclerosis. To avoid this, it is essential to be able to do breathing exercises. Read more in Chapter 13.
3. CALORIE RESTRICTION. The idea that a caloric deficit can prolong life comes from theories connecting longevity and metabolic rate. The authors and defenders of these theories believe that living beings are given a limited number of resources, including energy, which can be expended during life. Restricting caloric intake, leading to a slowing down of metabolic processes, helps to save "life force": figuratively speaking, a fire will burn longer if we toss small portions of fuel into it. There is evidence for the accuracy of such a view.
4. SLEEP CULTURE. According to the National Sleep Foundation, adults need 7 to 9 hours of sleep per night[22]. Young children need more hours to grow and develop (the younger the child, the more). People over the age of 65 need 7 to 8 hours of sleep.
Getting enough hours of sleep and monitoring its quality are two important aspects for those who want to achieve longevity and maintain their health. Sleep gives energy for mental and physical activity, contributes to the recovery processes, and strengthens almost all systems of the body.
Experts recommend always following a sleep regime, even on weekends, performing relaxing treatments before going to bed (for example, meditating, reading, taking a hot bath), avoiding caffeine or alcohol several hours before bedtime, choosing a comfortable quality mattress and pillow, maintain an optimal temperature and pleasant aroma in the bedroom, turn off lights and electronic devices (TV, computer, smartphone, etc.) an hour before bedtime.
Find out if you suffer from apnea (pauses in breathing during sleep), one of the most common causes of poor sleep. It increases the risk of high blood pressure and heart disease.
5. HEALTHY MIND. A healthy lifestyle is not just about exercising or dieting. It is also a concern for mental well-being and the development of cognitive skills. Such components of a healthy lifestyle as a positive attitude to life, stress management, and intellectual discipline (reading, language learning, and logic games), play a key role in maintaining mental health and increasing life expectancy.
One of the most effective methods to "free the mind" is meditation. It helps to shift attention from worrying about the future or fixing the past to the present moment and thus helps to interrupt the endless flow of negative thoughts and anxiety. You do not need to play appropriate music or light incense (this is optional) to start meditating, just find a quiet place and take a comfortable position. You can learn the meditation process yourself. For example, with the help of dedicated apps.
6. FEELING YOUNGER. Although health deterioration in the aging process is universal, people perceive and experience it in different ways. Scientists from Seoul National University, together with colleagues from Yonsei University (South Korea), concluded that feeling younger than you are is a major component of good health in mature years[23]. But the subjective feeling of being older, as MRI has shown, on the contrary, reflects a more rapid brain aging. This has also been confirmed by French and American scientists[24]. The study involved 17,000 retirement-age people who were followed for 20 years. It turned out that subjects who felt 8-13 years older had an increased risk of early death (by 1825 %).
7. GREATER SOCIAL TIES. It is almost impossible to keep track of long life without diseases alone, without the motivating force of family, friends, and loved ones. You can only do it with people supporting you. A person has a great opportunity to generate more resources, energy, and experience together with other people, which will necessarily affect not only the general quality of life but also the internal physiological and mental condition.
8. GOAL SETTING. People who know why they live have the best chance to live longer. Many studies confirm this hypothesis. Having a purpose in life is characteristic of the inhabitants of the so-called "longevity regions" places where people on average live longer than the population of the Earth. Dan Buettner, an American writer, and traveler, calls such places "blue zones." In a series of books on features of life in these amazing areas, Buettner points out that almost all blue zone inhabitants have special mindfulness practices allowing them to find meaning in life.
The inhabitants of the Japanese island of Okinawa have a practice called ikigai. This is translated as "something or someone that gives a person a sense of purpose or a reason for living." It is a person's main interest, the main aspiration in life. It answers the questions like "What am I doing here?" "Why am I living?" "How can I be useful to the world?" etc. Ikigai is a comprehensive notion running through life and helping to find yourself, your path, meaning, and purpose.
The inhabitants of another blue zone, the Nicoya Peninsula in Costa Rica, believe that a plan de vida is essential for a long, happy life. This term means a constant search for a reason to wake up in the morning, to enjoy every single day.
CONCLUSION
It is everyone's dream to live in a young body as long as possible. There is no universal recipe, practice, or panacea that can solve the problem of aging and premature death once and for all. The way to this dream is through the formation of many habits: sufficient physical activity, adequate nutrition, healthy sleep, as well as mindfulness practices allowing to boost optimism and define life goals.
And it does not matter which view of aging dominates now the "program" written in the genes, or the random accumulation of "breakdowns." Indeed, these theories allow us to understand some patterns and build a safety net in dangerous moments. At the same time, research shows that the main levers for managing life and youth prolongation are in our hands. That is why each of us can now take responsibility for our own lives and begin to create our own "blue zone."
BIOMARKERS OF AGING
CHAPTER 2
GENETICS
GENETICS IS EVOLVING MORE RAPIDLY: EACH YEAR OF DNA RESEARCH BRINGS MORE DISCOVERIES THAN THE PREVIOUS ONE. THIS SCIENCE HAS SPREAD TO MEDICINE, PSYCHOLOGY, ANTHROPOLOGY, ECOLOGY, AND OTHER FIELDS. IT HAS BECOME THE BASE FOR UNDERSTANDING THE HUMAN NATURE. GENETICS STUDIES THE BASIC MECHANISMS OF HEREDITY AND VARIABILITY, PROPERTIES THAT ARE COMMON TO ALL ORGANISMS. IT HOLDS GREAT PROMISE FOR PROLONGING A HEALTHY AND ACTIVE LIFE.
DEVELOPMENT OF GENETICS
Even though genetics as a science was formed only in the XX century, our remote ancestors had some understanding of heredity. Even thousands of years ago, people knew that certain traits could be passed from one generation to the next. Considering this, they crossed and bred animals and plants, improving their properties and functions.