Can you live to be 120

  All living things have a certain lifespan. We sometimes wonder why the human body can be used for decades or hundreds of years, which is longer than the life of cars and ships long?
  This is because the materials that make up the human body are constantly renewed over the course of life. The basic unit of human material is cells, and cells are alive. It is constantly metabolized, so that it is constantly replenished, repaired, and kept alive. In addition, the cells themselves are periodically renewed, producing new cells in the form of cell division to replace the old ones.
  Different cells have different cell division cycles, and they divide and update every few years on average. In the sense of cellular composition, no matter who you are, the “you of the present” and the “you of the past” are not the same person. Continuous metabolism, continuous renewal, and continuous acquisition of new vitality are the essence of the difference between living organisms and non-living organisms, and also the reason why our bodies can be used for decades or hundreds of years.
  So, don’t we live forever? Not also. Based on the current level of understanding, there are at least the following reasons that humans cannot achieve immortality.
  First of all, human life must be adapted to the external environment, and our living environment is not the most ideal, and some harmful factors often have adverse effects on the metabolism and renewal of cells; we must also deal with thousands of other organisms , especially microorganisms. Our bodies orchestrate a “symbiotic” relationship with these microbes, as many of our physiological functions require their help. If this symbiosis is out of balance, we get sick, not to mention that there are microbes we must keep out of, which are themselves disease-causing microbes.
  Second, despite our constant metabolism and periodic renewal, our cells still inevitably age gradually. On the one hand, the above-mentioned environmental factors may have toxic effects on cells, causing damage to their function and structure, and weakening their vitality; on the other hand, due to various internal and external factors, cells often make mistakes in the process of metabolism, division and renewal. Although the body has a powerful monitoring system, which is known as the immune system, it is still difficult to completely correct mistakes, and the result is the lesions of tissues and organs, or the occurrence of tumors. With the passage of time and the vicissitudes of life, the cells and tissues of the human body will gradually age, and the physiological functions will gradually decline, which we call aging. Aging is a gradual process that eventually leads to the end of life.
  Third, the number of cell renewals in a person’s lifetime is limited. Cells in some parts can be renewed frequently, such as intestinal mucosal epithelial cells, which are in direct contact with food, and will be renewed every few days; cells in some parts are not renewed for a lifetime, such as nerve cells in the brain, which cannot be renewed, only Maintain your own function and vitality through metabolism. Once the nerve cells in the brain are damaged, they cannot be repaired, and one less will die. With age, the number of cells decreases, the vitality decreases, and the decline of brain function is inevitable.
  Some scientists estimate the natural lifespan of human beings by calculating the cycle and number of cell divisions. In a person’s lifetime, the average number of cell divisions is about 50, and the average cycle of cell renewal is about 2.4 years. Therefore, the natural life expectancy of human beings is about 50×2.4=120 years old.
  The world has reported many longevity people who are close to 120 years old, which suggests that perhaps human natural life expectancy is longer than 120 years old. Since no one can live a lifetime in “ideal conditions”, we have no way of proving that a longevity record holder has achieved a natural lifespan. There is no such thing as a “death without a problem”. Human deaths can be attributed to disease, accidental injury, or premature aging.
  The so-called natural lifespan, also known as the “human lifespan upper limit”, was proposed as early as the 19th century. Its meaning is that if a person has an ideal living environment and behavior in his life, and excludes the interference of all unfavorable factors, how many years can he live at most? Since the beginning of the 21st century, with the progress of genetic medicine, more and more evidences suggest that the natural lifespan of human beings is determined by genetics. This means that when a person is born, his genetics dictates the maximum age he can live.
  The influence of genetics on lifespan was mainly studied by epidemiological survey methods in the past. For example, in some families, there are many long-lived elderly people in the grandparents and grandchildren. It is possible that the so-called “longevity gene” exists in the genetic code of this family. With such a gene type, it has strong resistance to cardiovascular and cerebrovascular diseases, malignant tumors and other diseases, and it is not easy to “age early”; in some families, generations of grandparents have premature coronary heart disease, cerebral infarction, In cases such as malignant tumors, there may be a lack of “longevity genes” in the genetic code of the family, or there are genes that promote the above diseases, and there is a strong susceptibility to these diseases that cause premature aging.
  The “Human Genome Project” made significant progress in the early 21st century, drawing and completing a standardized sequence of bases shared by humans, which is the “Human Gene Map”. At this point, we have been able to sequence and analyze the whole genome of each individual, so as to study the relationship between genes and diseases, and the relationship between genes and lifespan.
  Let us assume that human beings have never reached their natural life span, and that the causes of death throughout the ages can be attributed to disease, accidental injury, or premature aging. How much do genetic and environmental factors play a role in these causes of death? ? In response to this question, we can divide the causes of “premature” death into three categories.
  The first category, diseases that are completely determined by genes, are called single-factor genetic diseases, such as hemophilia, Down syndrome, and thalassemia.
  The second category is the cause of disease or death dominated by environmental factors, such as accidental injury, war, famine, plague, etc. These causes of death are largely determined by environmental factors, not genetically or only indirectly.
  The third category is diseases caused by the combined action of genetic factors and environmental factors, such as cancer, diabetes, cardiovascular and cerebrovascular diseases, chronic obstructive pulmonary disease, etc. It is now believed that the vast majority of diseases we know belong to this category, but in different diseases, the two play different roles.
  Among all causes of human death, diseases that are completely determined by genes account for about 1%; diseases or causes of death dominated by environmental factors once accounted for the largest proportion in human history, and currently account for about 18%; the remaining 81% of diseases Or the cause of death is caused by a combination of genetic and environmental factors.
  Today, the biggest problem facing medicine is how to deal with diseases caused by a combination of genetic factors and environmental factors, which we call chronic diseases. Chronic diseases have become the main reason for advancing human aging and restricting human beings to reach their natural lifespan.
  Once suffering from chronic diseases, such as high blood pressure, coronary heart disease, diabetes, stroke, malignant tumor, etc., even if a “clinical cure” is achieved, one has to take medicines and injections for life, and regular review is required, and the medical expenses are not low.
  Why are these diseases so incurable? Because their etiology is unclear, they cannot be explained by biological factors alone. The occurrence of these diseases is the result of a combination of biological, psychological, social and environmental factors. With the transformation of society, such diseases have shown an epidemic trend. In the 1950s, for every 10 people who died, only 2 died of these chronic diseases; now, 8 of every 10 people died of these diseases.
  In recent decades, the prevalence of chronic diseases in my country has risen sharply and has gradually become an epidemic. Taking the prevalence of hypertension among adults in my country as an example, it was about 5% in 1959, 13% in 1991, 18.8% in 2002, and 23.2% in 2018. According to the data released by the “China Cardiovascular Disease Report (2017)”, the number of patients with cardiovascular and cerebrovascular diseases in my country has reached 290 million.
  Another reason for the increased proportion of chronic diseases is the aging population. The occurrence of chronic diseases is not only related to genetic factors and lifestyle, but also has a great relationship with increasing age. In the early days of the founding of the People’s Republic of China, the average life expectancy of the people was only 38 years, and many people died of chronic diseases “before it was too late”. Today, “life is rare in the past seventy years” has long been a thing of the past. The proportion of the elderly population is increasing, and chronic diseases are also increasing.
  The problem now is that the entire healthcare system operates around disease, not prevention. When we mention “prevention”, we immediately think of the prevention of infectious diseases, because we have made brilliant achievements in the field of infectious disease prevention. In fact, most chronic diseases are preventable. The occurrence of chronic diseases is the result of the combined effect of genetic factors and environmental factors. While there is currently no way to control for genetic factors, we can control for environmental factors. If we work hard to create a good living environment for ourselves and develop healthy lifestyle and behavior habits from childhood, we can greatly reduce the chance of suffering from chronic diseases.
  The word “anti-aging” is very popular. In fact, preventing chronic diseases and correctly treating chronic diseases are the biggest issues of “anti-aging”. Starting from children, starting from me, everyone should prevent high blood pressure, diabetes, cardiovascular and cerebrovascular diseases, prevent cancer, and prevent chronic obstructive pulmonary disease. This is the correct way to fight aging.

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