In the process of reproduction of the population, or, in other words during the course of generations, mortality, along with fertility plays a major role. The death of each individual, taken by itself, there is a biological phenomenon, even though it was socially determined. Mortality - a massive process consisting of sets of individual deaths occurring at different ages and determine the order in its entirety extinction of real or hypothetical generation.
The statistical description based on establishing a connection between the quantitative characteristics of death and the age of people, give life tables. The calculation of mortality tables, along with other indicators receive life expectancy.
The value of life expectancy is calculated for all ages, but the most important is the life expectancy for a newborn. For complex features a lifetime this value is used in conjunction with the figures calculated for the different ages. Life expectancy is adequate general characteristic of the current level of mortality.
The most common measure of the intensity of mortality is the crude death rate, the simplicity and unity of the methods of calculation which (the ratio of the number of deaths to the average population per 1,000 people) allows for comparison of mortality rates in different regions of the world, one country in the dynamics for different periods of time. When people talk about high or low mortality, mean these figures. However, the overall death rate depends on the age structure of the population and therefore is not an accurate reflection of the level of mortality. But for each defined population at a given moment, this figure - an important feature, which are generalized expression of the actual demographic changes occurring in the population and influencing the growth of its population. Mortality and life expectancy are the main criteria that characterize the level of public health and thereby - the level and quality of life.
The process of extinction depends on the generation of a large number of biological and social factors of mortality (genetic, climatic, economic, cultural, political, national, etc.). From the point of view of demographic analysis of mortality, the most important division into two major groups: endogenous (generated by the internal development of the human body) and exogenous (associated with the action of the environment). Death is always the result of the interactions between these two groups, but the role of each of them can be fundamentally different.
Endogenous factors include biological components such person as gender and age. Itself belong to one or other sex determines the viability of the organism, which, as is known in women than in men. Age also reflects a certain degree of resistance of the organism, its resilience, wear and tear. Basically all of these indicators are biological. However, the decisive factor in biological components have certain social conditions that ultimately determine the level of age-specific mortality. But this level necessarily divided into two periods: the first - with the age when there is a continuous decrease in the risk of death (up to about 12 - 14 years), and the second - when it is a continuous increase.
Among the biological components include the nature and heredity, that is, the human genetic code. If it is due to the influence of the set of circumstances were favorable, it would mean that from a genetic point of view, the body has the prerequisites for long life. However, social conditions, among which that person will live or negate the favorable inclinations, reducing the natural vitality of the body, reducing the degree of resistance to harmful influences, or allow them to implement.
Action due to endogenous factors mainly aging organism. Therefore, endogenous processes arranged in a certain sense, their action is distributed throughout the life of each person is not random, not uniformly, but is concentrated in the older age groups. A number of degenerative related deaths hereditary diseases, birth defects and the like, there comes a young, often in early childhood. Although the rate of natural aging - the evolutionary characteristics of species, it is not the same for all people, have individual characteristics, so the age to which the viability decreases so that death is imminent, fluctuates within a certain range around the value called biological (species), duration of life. However, if we consider all the hypothetical curve of degenerative mortality rate of any population as a function of age, in general, the element of chance is negligible, and the probability of death from age - very big.
The impact of exogenous factors on the development of the mortality of the individual organism are usually disordered, random. Likely to be subject to such influences, as well as the likelihood that their power exceeds the protective ability of the body and result in death, are less dependent on age. Naturally, in any case more likely to die at the age at which a relatively steady stream of random external influences facing a less viable organism (in children and the elderly). At the same time, the effect of some exogenous mortality is only slightly dependent on age (for example, natural disasters, epidemics), and even lead to increased mortality in the most viable ages (wars, civil and industrial injuries, etc.). Therefore, when the value of exogenous mortality generally high, high, and the probability of accidental death in anyone, including in a mature, age. Enhancing the role of the endogenous factors of mortality is equivalent to limiting the role of chance in the process of extinction of generations and increase in life expectancy.
Speaking of endogenous and exogenous factors, it should be noted the inseparable connection of the organism, the development of its internal functions to external influences, with the habitat of man. In this context it is possible to allocate "predominantly endogenous" and "predominantly exogenous" factors not absolutizing external or internal component of the pathogenesis of each of them. It is clear that, for example, a severe infection or injury are exogenous nature, but with the same severity of a young healthy person is less likely to die than old or sick. Thus, endogenous factors alter the probability of death from exogenous causes and, on the contrary, the strong negative impact of external sphere hastens death from endogenous factors.
During the radical reconstruction of the human environment created new cumulative impact of exogenous factors (eg, due to pollution). Mental and emotional overload have become a fixture of city life, causing an increased incidence of psychosomatic.
People for life is constantly exposed to a variety of external factors, which enhance endogenous development of the aging process and reduce the viability of the organism. Gradually accumulated, endogenous factors cause death, usually in the older age groups. The idea gained, the cumulative effect of exogenous factors falls E.M.Andreevu, and they also introduced into scientific concept kvaziendogennoy deaths occurring as a result, and under the cumulative impact of environmental and social factors.
By combining different among themselves, mortality factors are responsible for the direct cause of death, that is, a particular disease, trauma caused by the disease process, which led to death.
A characteristic feature of the modern cause-and-effect relationships that form the life expectancy of the population in developed countries is rapidly dominating influence of endogenous and kvaziendogennyh factors which are closely related to mortality from chronic diseases. Typically, in most countries, with a decrease in overall mortality rate of mortality from these increases in middle and older ages.
Among the endogenous and kvaziendogennyh causes include diseases of the circulatory system, neoplasms, gastric and duodenal ulcers, liver cirrhosis, diabetes, nephritis, and the like. Mainly exogenous causes of death - is infectious and parasitic diseases, diseases of the respiratory, digestive, accidents, poisoning and injuries. Understanding the specific factors of mortality - an important step in the study of its laws and the possibilities of increasing life expectancy.