Old Age

OLD AGE, a stage in the development of an individual, accompanied by characteristic morphological changes in all systems of the organism and the suppression of all functions of the latter. Complex multicellular organisms undergo a series of significant changes during their life, both in anatomical and functional respects, and reflecting these changes, their habitus also changes with age. The skin of the face in old age is dry, wrinkled, for the most part pale, and thinned, as a result of which blood vessels and tendons show through it; the hair on the head is gray; the eyes lack luster; there is a lack of teeth in the mouth; the back is more or less hunched (kyphosis); old people walk slowly and with difficulty—these are some of the most striking external features of advanced old age. Vision and hearing in old age decline; complaints of feeling cold are frequent. Height and body weight decrease. According to numerous measurements, a man between 50 and 85 years of age decreases in height by more than 3 cm, and a woman by more than 4 cm, due to the reduction of the intervertebral discs (see Spine, anatomy). Sometimes the height of old people decreases by 6 or even 7 cm. Body weight, according to Quetelet, reaches its maximum value in men by age 40 and in women by age 50. From age 60, it begins to decrease, and by age 80, it falls on average by 5 kg. It is often thought that hair loss is characteristic of old age, however, this is not entirely true, since people most often begin to go bald at an earlier age; in old age, they only continue to lose hair, and those who did not begin to go bald in youth or middle age have a good chance of retaining their hair even in old age. Old age leaves its mark on the external appearance of an individual to a far from equal degree in different species of animals; in most mammals, it is sufficiently vivid and characteristic; in birds, and especially in reptiles, it is significantly less pronounced. Advanced old age is usually accompanied by so-called senile marasmus, which amounts to sharp phenomena of exhaustion and withering of the organism, depending on profound anatomical and functional changes, united by the concept of senile involution. Anatomical changes can be briefly characterized as senile atrophy with a simultaneous tendency toward sclerosis, while functional changes are characterized as the withering of all bodily functions on the basis of a disturbance in the balance of the processes of creation and destruction. A striking indicator of such a disturbance is anorexia, a sharp decrease in appetite, testifying to a decrease in the intensity of the vital energy of tissues and their need for food. Senile atrophy represents a complex of regressive changes consisting of a decrease in the volume, and partly in the number of cells, with the simultaneous presence of a number of physical and morphological changes in the cellular protoplasm (browning, hardening, drying, etc.), in the thinning of the skin, bones, and cartilage, the disappearance of adipose tissue, the emptying of a significant number of capillaries, and a decrease in the extensibility and elasticity of tissues. The organs of old people differ from the organs of young subjects by their darker color and smaller size, and at the same time, greater density (proliferation of connective tissue). However, atrophic processes during senile involution are distributed unevenly among organs, and each of them, as is customary to say, has its own mature and senile age. Thus, the thymus, as is known, begins to involute by the period of puberty, and in adults at the age of 25–30, it is not always possible to macroscopically detect even the remnants of this organ. The ovaries, after the cessation of menstruation, begin to decrease in size, and in old women, they have the appearance of small, dense, wrinkled bodies. With the extinction of the menstrual cycle, the uterus also decreases in size. The involution of the thymus gland and the uterus depends on special endocrine factors; generally speaking, the pace and sequence of senile involution of tissues and organs are determined mainly by the degree of their differentiation, i.e., tissues undergo greater regressive changes with age the more complex their differentiation and functional purpose. Therefore, epithelial tissue is the least subject to senile involution, muscular tissue is more so, and nervous tissue is the most. At the same time, senile atrophy of the brain by no means inevitably leads to the psychic disintegration of the personality. A clear mind and capacity for work can be preserved until deep old age. The weight of the brain progressively falls (see Brain, weight of the brain). More specifically, by organ, senile atrophy is expressed in the following changes. In accordance with the decrease in brain weight, the cerebral convolutions in old age are noticeably atrophied, the sulci of the brain are widened, the cerebral cortex is thinned, the ventricles of the brain are somewhat widened, and the amount of cerebrospinal fluid is increased. In nerve cells, there is pigmentary-fatty degeneration and atrophic changes. In the circulatory system, there is a picture of athero- and arteriosclerosis, and on the part of the heart, myofibrosis, consisting of atrophy of the heart muscle fibers, with their replacement by connective tissue. The work of the heart is hindered due to changes in the vessels, and the functional capacity of the heart is lowered (a tendency toward hyposystole and some bradycardia). These changes cause insufficient blood supply and nutrition of organs with corresponding clinical symptoms: weakening of memory, dizziness, weakness of the arms and legs (this weakness is determined, however, not only by the deterioration of blood supply, but also by changes in the muscle tissue itself), and progressive cooling of the body surface, giving a sensation of feeling cold (the latter, however, also depends on a decrease in heat production, manifesting in a certain lowering of the general body temperature). Vascular changes, in turn, create a predisposition to thrombosis and apoplexy. Deviations on the part of the vascular system have long been attributed the most serious significance in illuminating the symptomatology and even the pathogenesis of old age (Casalis's aphorism: "Our age is the age of our arteries"), and in particular, Demange's theory was ready to reduce all senile changes to the aforementioned changes in the arteries. Such a point of view, however, suffers from some exaggeration, because, on the one hand, there are cases when, despite advanced age, the vessels turn out to be in a relatively satisfactory condition, and on the other hand, early atherosclerosis is usually not accompanied by the typical picture of old age. Finally, it should generally be kept in mind that the problem of vascular atherosclerosis and the problem of old age do not necessarily coincide in time. One can only speak of the prevalence of atherosclerotic processes in old age. In striated musculature, a picture of brown atrophy is observed with thinning of muscle fibers, deposition of brown pigment, and atrophic proliferation of nuclei. Muscle fibers long retain their striated structure, but eventually, it disappears and is replaced by a shapeless mass among a large number of proliferated nuclei. The amount of adipose tissue between muscle bundles decreases or disappears entirely. These changes in the muscular system make the muscle weakness and rapid muscle fatigue of old people understandable. In parenchymal organs, along with the atrophy of parenchymal elements, there is a proliferation of connective tissue, leading to their sclerosis and, in turn, reinforcing the former. Some authors speak in this regard of a "true excitation" of connective tissue. This process most often leads to a decrease in the volume of organs, but in some cases, such as in the prostate gland, the volume of the organ may increase due to powerful proliferation of connective tissue. In contrast to the state of parenchymal organs in old age, there are senile changes in the skeletal system: by analogy with the hardening of parenchymal organs, individual elements of the skeletal system also show a tendency toward consolidation (fusion of bones, e.g., vertebrae, depending on the ossification of the parts separating them; ossification of most cartilage); however, despite this, the bone skeleton itself becomes lighter due to a decrease in the amount of mineral salts in it. The aforementioned changes in the skeletal system also explain the kyphotic curvature of the spine in old people; as for the atrophy of the lower jaw, it is linked to the loss of teeth (atrophy from disuse; lack of pressure from the teeth). Senile emphysema of the lungs is caused to a significant degree by regressive changes in the elastic fibers located in the walls of the alveoli. These fibers appear significantly thickened and tortuous. The same factor, i.e., regressive changes in elastic fibers, gives a peculiar character to senile skin (see). General atrophy of the body makes the aforementioned fact of the decrease in total body weight and height in old age understandable.

Physico-chemical changes in the aging organism, partly already mentioned above, boil down to the following: 1) a lower water content in the tissues (the total water content in the body tissues decreases as aging progresses, consequently in Old Age a shift towards dryness is noted); 2) a decrease in the ability of tissues to swell; 3) a decrease in elasticity with a simultaneous increase in the hardness of connective tissue formations (sclerosis); 4) a decrease in resistance to fracture and rupture; this applies primarily and mainly to bones and at first glance could entirely be attributed to a decrease in the inorganic components in the skeletal system, however, according to Mason's data, fluctuations in the amount of ash in bones are not to such a degree in a regular relationship with age as the physical strength of the colloidal framework of the bones themselves, while the ability of muscle tissue to stretch in youth, middle, and old age relates to one another as 7:3:2 (Landois-Rosemann); 5) a decrease in the transparency of some tissues (senile clouding of the refractive media of the eye); 6) a decrease in the diffusion permeability of tissue barriers; 7) a decrease in the dispersion of colloids and colloidal protection against the formation of precipitates and in particular against the precipitation of calcium. The latter is always found in tissue fluids in a supersaturated state, however, only in Old Age, with the decrease in the dispersion of colloids, does it physiologically acquire a tendency towards the formation of precipitates, and one can speak of a real displacement of Ca in old age (extraction from bones and deposition in the walls of arteries, cartilages, etc.). The decrease in the dispersion of tissue colloids and the permeability of cell membranes, in turn, must lead to a decrease in oxidative processes. In general, the nature of the changes in tissue colloids in Old Age can be briefly designated as a transition from sol-like formations to gel-like ones. Among the functional deviations characteristic of old age and briefly characterized by signs of hypotonia and hyposthenia (cardiovascular, muscular, nervous, etc.), one phenomenon deserves special mention, standing somewhat apart: this is the low need of old people for sleep, in particular for night sleep, with noticeable drowsiness during the day. And if the latter can be considered without further deepening as an expression of general weakness, the former does not lend itself so easily to explanation (see Sleep). Old age is characterized by a predisposition to a number of diseases and, conversely, other types of diseases less often affect this period of life or proceed in a milder form. Atherosclerosis with all its consequences, cancer and cataract, hypertrophy of the prostate can serve as examples of the first kind, tuberculosis of the second kind of diseases. The reasons for such a difference should be sought in the peculiarities of both the age-related changes of the organism and the etiology and pathogenesis of the disease forms (summation of harmful effects on the vascular wall, and perhaps also shifts in cholesterol metabolism for atherosclerosis; a tendency towards fibrous processes, and perhaps also a weakening of the secretion of the sex glands for tuberculosis, etc.). Tuberculosis in the elderly does not always proceed mildly; the opposite is also observed; sometimes the infection takes on an exudative and, moreover, generalized character, reminiscent of similar manifestations of childhood, in particular the so-called organ tuberculosis. In Old Age, there is also observed a certain decrease in the brightness of symptoms in acute infections in the sense of, for example, temperature reaction, skin rashes, enlargement of the spleen, lymph glands, etc. The onset of Old Age with the entire complex of changes characteristic of it is usually preceded by a period of precursors, a kind of praesenium, characterized either by the appearance of one or another sign of Old Age, only in a less bright form and, moreover, not exclusively associated with the latter (graying of hair, progressive increase in fatigue; a fall in libido, etc.), or by such phenomena specific to this period of life as certain changes in vision [presbyopia (see)] and the reproductive system (climax). The causes of senile withering with all the consequences flowing from it have not yet been fully clarified. Weismann, Minot, and Bühler were ready to reduce it to a weakening, and then to a loss by cells of the ability to reproduce, as a result of which, in the opinion of these authors, the organism must in the end lose the ability to replace lost substance. Minot even thought to find an anatomical substrate for such degeneration of cells in the disruption of the supposedly normal ratio between the nucleus and protoplasm, of which the former supposedly gradually decreases in Old Age, and the latter, on the contrary, increases. However, such an opinion can hardly be accepted unconditionally, and if one cannot call convincing Metchnikoff's reference to the fact of the preservation of the ability to grow even in deep Old Age by such appendages of the body of epidermal origin as hair and nails, which are in no way capable of influencing the longevity of the organism, then, on the other hand, one cannot ignore the somewhat unexpected fact that the heart, as it turns out, continues to grow until deep Old Age. In general, in Old Age, the processes of destruction nevertheless begin to outweigh the processes of creation: the intimate side of this phenomenon, however, is not revealed by the indicated point of view. Metchnikoff saw the essence of Old Age in the disruption of tissue equilibrium, in the struggle of the "noble" elements of the organism with macrophages—a struggle that intensifies with age and leads to the gradual destruction of the former by the latter. He saw the cause of the weakening of the resistance of the "noble" elements of the organism, and in particular nerve cells, in Old Age in various kinds of intoxications, but primarily and mainly in intestinal self-poisoning. However, the very fact of the struggle with macrophages, as Metchnikoff depicts it, is still subject to doubt. In particular, in the brains of old individuals, one does indeed have to observe pictures that give reason to speak of neuronophagia, but what is the primary moment here—whether the aggressive activity of macrophages or the independent loss to a certain extent of their vital activity by nerve cells—is difficult to decide in a number of cases; it is more correct to incline towards recognizing the second possibility in view of the very discrepancy between the degree of degradation of the nerve cell and the severity of phagocytosis (clearly expressed atrophy with insignificant accumulation of macrophages around it), so that neuronophagia in such cases would be more correctly considered not so much as an expression of active aggression on the part of macrophage elements, but as a more passive process of substitution of one tissue by another. There exists an endocrinological explanation of the problem of Old Age, with some putting the role of the thyroid gland in the first place in this regard (Lorand), while others (Steinach, Voronoff) put the sex glands. Some attention is also paid to the adrenal glands. However, no matter how indisputable the enormous role of the sex glands in the life manifestations of the organism and in particular in the change of age-related changes is, and no matter how interesting the results obtained in this direction are, the following two facts should still dictate somewhat greater restraint in assessing this factor. Firstly, in childhood, sex secretion is still very insignificant, and yet this very age is a period of maximum liveliness, mobility, and indefatigability; on the other hand, examples of the preservation of mental freshness and physical vigor in deep Old Age with almost complete withering of sexual functions are not so rare. Finally, castration, widely practiced in animal husbandry, does not lead to the phenomena of Old Age, just as eunuchs in many respects are not yet old men. Since the animal organism is nothing more than a complex of colloids, in essence, the problem of Old Age boils down to the problem of the "aging" of colloids. It is known that colloidal solutions harbor a tendency towards flocculation, and the sol gradually passes into a gel. Incidentally, along with cells, the intercellular substance must also change in the indicated direction with age and thereby hinder both the supply of nutritive material to the latter and the outflow of metabolic products from them, which in turn must lead to autointoxication. True, there is still a difference between living and non-living colloids in that in the former, metabolism is constantly occurring and new particles come into play to replace the worn-out ones. It is possible that the dominant role in the process of senile degradation falls, as some authors think (Marinesco, Milman), on brain cells, which, in Milman's expression, stand in relation to the whole organism in a similar way as the nucleus to the protoplasm in a cell. The cited considerations, however, do not entirely solve the problem of Old Age. The animal organism does not represent a mechanical aggregate of cells and tissues, but unity and integrity are characteristic of it. After all, individual tissues and organs, as experiments with tissue cultures and on isolated organs show, according to Kravkov, can under certain conditions continue their existence even after the death of the organism as a whole. It is precisely in this plane, i.e., in the aspect of studying the laws of the development of the organism as a certain unity, that an approach to solving the mentioned problem is just as necessary.

Meanwhile, very little is known in this direction to this day. Some scientists have made attempts to establish, for example, a law of life expectancy based on the animal's growth period (according to Buffon, this coefficient is 6 or 7; according to Flourens, it is 5), but it is quite obvious that such attempts, while not uninteresting in themselves, do not go beyond the empirical observation of the existence of a certain regularity of the phenomenon, without, however, clarifying in the least the inner meaning of the relationship. The latter, however, relates not so much to the question of individual aging and the difference in individual longevity, as it does in particular to the question of species longevity.