Sociologically speaking, the phenomenon of population is extensively changing naturally, or by artificial means. World population has been changing from 500 million people in 1650. Through progress in science and technology, the speed of population change has ever increased. While the world population was 1 billion in 1800, it grew to 7.9 billion in 2000. Population increase was unexpected during the past two centuries, much due to improvement in quality of life with reference to medical services. Since the year 2000, growing of population slowed mainly to reach higher quality of life. In spite of slowing population growth in industrial world, many developing countries have continued their population growth since 1950 due to their access to medical facilities. Because of literacy increase and more educational development of the youth, especially the women, birth rate is slowing within the new generations through which the new families are exposed to higher quality of life. In other words, younger generations have come to know that their better quality of life is subject to families with fewer members. Currently, there is a sort of competition within the population to access higher/ better quality of life with special reference to the developed world.

Sociology as a social science looks at the affectability of societies under the factor of population change. Population change is currently taking place all over the world with fluctuations. Such a change is more observed in more developed world rather than the less developed ones. Factors such as education, women's employment, more rights for women, medical facilities towards women, counseling, and many more have caused population change to happen. Since 1900, many world countries have come to know that by declining population growth rate, they can have more access to development, and the cycle continues. In this way, per capita food, hygiene, income, and many more would increase. Currently, people in Asia are trying to change

their population any way possible. For example, it is widely observed among the younger generations in India, China, South Korea, etc. Recently, many developing nations have adopted policies by which to achieve population change. In general, declining birth rate ultimately leads to an increase in the elderly population in a given society. Such a phase of population change needs its own planning and arrangements. Sociologically speaking, demographic change leads to more needs, and such a change involves fluctuations in quality of life, etc. A developing country is a sovereign state with a less developed industrial base and a low Human Development Index (HDI) relative to other countries (O'Sullivan, 2003). There is also no apparent agreement on which countries fit this category (Composition of Macro, 2010); (Should We Continue to Use the Term "Developing World", 2015). About one-third of population in urban world living in slums, is widely problematic. According to UN-Habitat, around 33% of the urban population in the developing world in 2012, or about 863 million people used to live in slums (State of the World's Cities Report, 2012/ 2013). On the other hand, and in general, quality of life is the perceived quality of an individual's daily life. That is, an assessment of their well-being, or lack thereof. This includes all the emotional, social and physical aspects of the individual's life including health-related quality of life (CDC-Concept); (Bottomley, 2002).

Demographic change is inevitable today. While most societies have adopted policies to reduce their birth rates, we still see communities that are constantly experiencing an increase in births and consequently an increase in population. The first group or countries that have generally limited their populations have faced higher living standards and general satisfaction in various fields, while the second group or communities with more births; They generally have a lower standard of living. The result of such a process is a reduction in living standards and the incidence of diseases and challenges in these societies, even in the future. Therefore, in order to have a quality society as well as effective and quality women and men in the future, population planning must be done effectively in each society. To achieve this, appropriate social researchers and sociologists must always be empowered, and their capabilities must be used. In general, the declining birth rate ultimately leads to an increase in the elderly population in a given society. Therefore, the phenomenon of aging itself is due to the adoption of new demographic policies in recent decades in different societies. In this article, we will evaluate the population and its impact on quality of life.

Methodology used in the present article is of qualitative type. In that, various paradigms have been used to find out about the facts regarding pandemics during the history. Qualitative research usually studies people, events or areas in their natural settings. In finding facts for the research, the researcher engaged in careful data collection and thoughtful analysis of what was relevant. In the documentary research applied for the present research, printed and written materials were widely regarded. The research was performed as a qualitative library-type in which the researcher had to refer to the relevant and related sources. In the current research, various documents were thoroughly investigated, and the needful inferences were made. The data fed by the investigator in the present article is hopefully reliable. Though literature on pandemics is very limited, yet the author tried to investigate many different resources in order to elicit the necessary information to build up the text.

Population aging
There is a fact that as the birth rate decreases, we see more people living; Therefore, following the declining population trend, a longer life expectancy can be expected from the remaining population. The United Nations has designated 1999 as the International Year of the Elderly (IYOP), a phenomenon facing the industrial and non-industrial world. The International Year of the Elderly itself reflects a new roadmap in the study of aging (Chappel: 1999). Population aging is one of the main issues in demographic change today. On the other hand, following a reduction in births, more potential material opportunities are provided, and in the form of it, the quality of life improves. The result of such a movement is greater population survival, or in other words, an increase in the elderly population in a given society. Iran is facing this phenomenon today, and it itself needs more monitoring, more investment and more population.

This means that the elderly population should be supported by the working age population, which is generally called the dependency burden. Today, in many societies where the number and proportion of older people has increased, they are generally supported and cared for by lower age groups; Otherwise, public or private organizations should provide the necessary support to this population. On the other hand, the burden of dependence of the elderly population in various ways, as well as their maintenance, promotion and quality of life must always be provided by families, lower age groups or governments. Hence, demographic change itself leads to more needs. Because less developed countries have recently encountered the phenomenon of aging, they do not have much experience in this regard; The elderly in such societies are faced with many cases of various deficiencies and inadequacies, which themselves need more revision and support.

These demographic interactions involve changes and fluctuations in quality of life. Decreased birth rates, ultimately by changing demographic indicators and modifying such indicators, itself leads to an increase in the elderly population in a given society. Also, the emergence of such changes improves the quality of life. On the other hand, demographic policy makers generally make changes in demographic indicators in order to achieve greater welfare, higher quality of life and more security in various sectors. Such a movement began during the twentieth century in developed societies; In a way, this has led to the reform of many economic, social and welfare indicators in those societies. It is noteworthy that the adoption of such policies in developing societies has generally begun since the 1950s. It is noteworthy that less developed societies still have a long way to go to achieve a relatively desirable or ideal quality of life.

While countries such as the United Kingdom have seen population change for the first time; In 1916 it will have 12% of the population aged 65 and over, in 1997 it will have 19% of the population aged 65 and over, and in 2020 it is projected to have 19% of the population aged 65 and over. Not only the United Kingdom, but other industrial societies in general are in a similar situation. Such societies throughout the twentieth century have always pursued appropriate policies and advocates for different segments of the population; Today, various population groups, including youth, middle-aged and elderly, enjoy welfare, employment, social security, and a satisfactory life; That is, a set of conditions that have implicitly brought them a higher quality of life. Hence, the establishment of more industrialized countries can itself encourage less developed societies to achieve a higher quality of life. Thus, social, cultural, and communicative communication of this kind can itself help less developed countries in various ways; In such a way that by adopting appropriate social, economic and health policies and plans, such societies will reform their structure in different dimensions, and eventually will achieve better quality age groups. Such interactions are mainly based on demographic indicators and reforms.

This trend of aging is common throughout Europe, and perhaps it is a boon for countries with young populations. The aging of the population in various ways in industrial societies has caused such countries to face a shortage of manpower and a young population; That is why immigration, especially the acceptance of the young population by such aging societies, has always occurred in recent years. Thus, the aging of the population in its industrialized countries to a large extent provides employment opportunities for the young population of less developed countries. Today, this trend has largely solved employment problems in both categories of countries (developed and developing countries); This move has greatly affected the quality of manpower of developing societies. Young people and immigrants accepted in industrialized countries also help their families financially and economically, and this in itself has a significant impact on their quality of life.

This theory itself is also proposed and defended; This means that today's seniors, who have contributed to the existing prosperity and well-being, have the right to a high pension. Many sociologists are advocating for the elderly because the advances of the present age are the result of their past efforts. Therefore, the provision of a decent life, pensions and adequate rights as their inalienable right is approved by many sociologists, geriatricians and the like. Industrialized countries, which are already more familiar with the phenomenon of aging than other societies, have provided more services and amenities for their elderly, and thus have maintained their quality of life to a considerable extent. However, less developed countries, which have recently encountered the phenomenon of aging, have not been able to provide satisfactory welfare and social security services for their elderly, thereby significantly improving their quality of life in old age. 

Dependency load
The growth of the dependent population leads to higher taxes for employed people; That in itself leads to higher wage demand; That is, a situation that somehow leads to economic inflation, leads to a lack of competition, leads to unemployment and eventually leads to a cycle of poverty of this kind, the combination of these conditions leads to a decline in quality of life. Modernization theory introduces developed industrial societies as a model for less developed countries, and suggests that less developed countries should adopt the same policies used in industrial societies (Neysmith and Edwardh: 1983). Today, the growth of the dependent population, especially the elderly population, has led to many problems and contradictions; In such a way that the increasing livelihood burden of this population is generally borne by the active population; A situation that itself does not have positive and satisfactory economic consequences. Therefore, planning systems in different societies must operate in such a way that the economic burden of the growing elderly population is less borne by the family; As a result, the quality of life for both ordinary families and the elderly will be strengthened.

Industrial societies have largely provided these conditions for the elderly during the twentieth century. This is while developing societies still have a long way to go in this regard. The burden of aging dependence due to the increase in the elderly population, especially in developed countries, has led to the establishment of a pension system for men and women 65 and older. This advantage is an achievement of the nineteenth and early twentieth centuries in industrialized countries. The establishment of a continuous system within industrial societies has led to the elderly enjoying greater prosperity and security in retirement and disability. This has given them a longer lifespan. This trend has gradually spread to many newly industrialized countries as well. It should also be noted that experiences related to the pensions of countries and industrial societies should always be reviewed and analyzed by less developed societies. Likewise, the electronic revolution has led to more goods being produced by the people or manpower today. Thus, the problem that arises; This is how many people can easily meet their needs; That is, the machine has taken the place of manpower to an advanced degree. This trend or phenomenon needs a lot of in-depth study, part of which is related to sociology and population planning; Otherwise, the crisis of unemployment and inability to provide for oneself will become more widespread in the coming years.

Although the financial problem of the elderly, especially in industrial societies, has been largely resolved, the aging of the population itself has led to related issues such as the isolation of the elderly, generally following the disappearance of extended families. In such situations, the elderly have to either live independently or live in nursing homes with their peers. This stage of life has affected their quality of life in various dimensions. Because in the past the family was different from the present; That is, many seniors live naturally in extended families; That is, families in which several different generations lived together and next to each other, in such circumstances, there was no such thing as aging as it is felt today. Today, however, following the economic, social, and cultural development of societies, families have generally become smaller and more nuclear; In such a way that only one generation lives with or without their child (s). Such conditions have made the situation of the elderly very difficult; That is, they have to live alone and independently, or in centers with similar groups. This set of conditions has affected their quality of life. It is also worth noting that today the elderly need to be more supervised and planned in order to maintain a very satisfactory quality of life.

Loneliness and feelings of worthlessness combined with relative poverty reduce the quality of life of many older people. This phenomenon can be seen today in all societies, both developed and developing. What is certain is that the planning and social service systems should provide such conditions for this population so that the feeling of worthlessness does not spread among the elderly, and as a result their quality of life can be maintained at a satisfactory level with comprehensive economic support, care and the like. . Because the elderly are generally active before entering this course, and use their abilities in various ways, by entering this course, they feel marginalized by looking for physical and mental loss. If this situation is not addressed, the elderly will more or less have mental problems. Therefore, the planning system, while paying special attention to this population, must also make sufficient investments to support them.

Over the years, extensive efforts have been made to delegate tasks such as the great role of parents to the elderly; In such a way that they take care of their grandchildren. Unfortunately, in societies where young people are increasingly in control, the elderly are considered insignificant. As the proportion of the elderly population has increased in many societies in recent decades, governments and planning agencies have been constantly trying to delegate new tasks to grandparents; That is, caring for grandchildren within the family and the like. This is the case in many industrialized countries today, and efforts are being made to make young people pay more attention to their grandparents; In such a way that they do not feel less dependent in their old age, and thus do not feel like a burden on their families or younger age groups. This will increase the quality of life and happiness of the elderly.

Population and urbanization changes
Over the past two centuries, following demographic change, urbanization has also taken an increasing trend; In a way, today many citizens depend on the city for shopping, education, entertainment and leisure. The increase in population without proper investment in the economic and industrial sectors in recent years has led to an increase in urbanization, especially in developing countries. Immigrants to such cities generally migrate for higher incomes, greater prosperity, and access to more services; That is, a situation in which they can improve their quality of life. In general, the process of living in a city and its dependence is called urbanization itself. Thus, urbanization can be controlled and controlled in a situation where balanced development takes place, and many amenities and services within large cities reach smaller locations. Similarly, by balancing quality of life indicators, the spread of urbanization can be prevented. Demographic change itself indicates a larger share of the population in urban areas. This movement initially reduced mortality, improved public health, improved nutrition, control of communicable diseases, etc. in Europe (Braudel: 1981).

The expansion of urbanization has also left many elderly people in the cities; That is, a population with a different quality of life. As urban areas have generally had higher amenities and services in recent decades, this has led to more people in these areas having a better chance of aging than in other areas. On the other hand, large cities, which generally attract specialized manpower, the parents of this skilled manpower often migrate to larger cities in search of their children. The sum of these conditions has increased the aging ratio in large cities; That is, places that have a higher quality of life. While the phenomenon of urbanization and aging first began in industrial societies, it has gradually spread to developing societies as well. Therefore, demographic change should always be on the agenda of social planners and policy makers, urban planners and other relevant institutions.

Social issues
The growth of urban areas or a set of urban areas has led to many issues related to health, pollution, road congestion, non-standard housing (standard) and the like, which itself affects the lives of all classes, especially the elderly and their quality of life. Therefore, their social problems are largely due to environmental issues, high urban population density, irregular migration within cities, suburbanization and the like. This set of cases in some cases leads to abuse of the elderly. Researchers support the need for interventions and strategies to help abused and problematic older people (Lithwick et al. 1999; Nahmiash and Reis: 2000).

Today, many cities in developing countries, due to their population growth in recent years, have faced many problems caused by population, which has led to many social problems and the resulting damage. For example, the high population density in the big cities of developing countries, among many other issues, has also led to environmental pollution; That is, a phenomenon that has a great impact on different age groups, especially the elderly. This process generally adversely affects the quality of life. Therefore, keeping the population in proportion, especially within cities, and forecasting it for years to come, can itself serve as a guarantee of a high quality of life.

Such urban areas raise more or less immeasurable problems; In a way, alienation within cities in some cases even leads to an increase in suicide among citizens (Sainsbury: 1955). Large cities generally face different citizens; That is, spaces in which there is less equality and compatibility between citizens. On the contrary, in the conditions of heterogeneity of population within such geographical spaces, a kind of alienation and in other words individualism appears within such societies; In such a way that in some cases the mentioned social and demographic structure itself becomes a kind of crisis and social problem. Therefore, keeping urban areas coordinated in terms of quantity and quality of population can greatly increase and lead to the social and mental health of citizens. The mentioned situation (quantitative and qualitative coordination of the population) leads to the improvement of quality of life and social health.

Such urban areas generally lose the strong network of kinship, and are replaced by the network of friendship (Young and Wilmot: 1960). In any case, following the emergence of a new urban landscape in which the kinship network has been weakened in various ways. The replacement of the friendship network should be strengthened and encouraged as much as possible, in order to prevent crises and potential dangers of alienation. In such cases, the application of social planning should be done as accurately and with sufficient skill; That is, a set of conditions that help to improve the quality of life of citizens.

At the same time, all kinds of crimes, vandalism, etc. are more visible in such urban areas than in smaller ones, and that endangers the security of citizens, including the elderly. The expansion of urban areas generally has different consequences and effects; There are a variety of crimes, large and small, overt and covert, including vandalism in various forms, within immigrant cities. In addition to the above conditions, the urban environment in large cities within large cities in recent years has been exposed to a variety of hazards; That is, a phenomenon that causes various harms to different age groups; Such as environmental pollution. The phenomenon of vandalism is also evident within large and predominantly immigrant cities. Vandalism means the destruction of the environment and its various facilities, intentionally such as cutting down trees, destroying green space, destroying property such as public telephones, destroying vehicles such as buses, etc.

Internal migration
Another result of demographic research is internal migration, which is followed by economic pressures. In the face of limited job opportunities in smaller geographical areas, many jobseekers are migrating internally to meet their current needs. This is the case today in many developing countries in Asia, Africa and Latin America; That is, a stream that itself carries with it both overt and covert harms, and potentially many; And with the motivation they migrate in order to achieve a higher quality of life. Compared to other demographic factors, migration has less effect on population aging (Moore et al. 1997), in contrast to reduced fertility rather than migration, it causes more population aging (Denton et al. 1998).

During such migrations, young age groups turn to areas of economic prosperity, both industrial and service. This allows active and generally skilled age groups to move from smaller geographies to larger cities. Such a situation affects the balance between different cities and different parts of a country in terms of population, health, social health and the like. Therefore, such policies should be adopted, so that young people can gain more jobs in their hometowns. It is noteworthy that the creation of such conditions requires macro-development programs at the national level; Otherwise, developing countries will have to expect massive migration in the coming years.

This (internal migration) disrupts the demographic, social, cultural, etc. balance, in which the elderly largely lose their security. In order to advance development goals in the general sense, the balance of the population, both men and women, in different age groups in different parts of a country must be established; In a way that human and non-human capacities and skills can be used to the desired extent. Under such circumstances, the general quality of life also improves.

Balance between the sexes
Various factors have been mentioned as to why women live longer than men. They are:

1) In addition to biological (biological) factors that make women live longer, many other social factors are effective in women's longer life expectancy. Social factors such as social capital, higher literacy and education, increasing the age of marriage and subsequent decline in fertility among women, and such factors, each in its place along with biological factors, have caused women to compare with men from Have a higher life expectancy; It is a process that itself requires the necessary measures to maintain and improve the quality of life of women, especially in the age of 60 years and above.

2) Because women today and in the urban-industrial world accept almost masculine roles, the resulting tensions and pressures cause many cases of burnout and depreciation between them, and ultimately affect their life expectancy index. While this situation is prevalent in most societies of the world today, the industrialized countries themselves have adopted superior and pro-women policies to ensure their health as much as possible. Reduction of women's working hours, their retirement at a younger age compared to men, provision of health, medical, education, etc. facilities; These are among the factors that have made it possible for working women to maintain their higher life expectancy compared to men in urban-industrial societies.

3) Because men are more prone to accidents, they use more tobacco and also put more work pressure on them; The combination of these factors has made women more vulnerable to disease and mortality compared to women. In the past, this closer balance was simply due to the fact that women were more likely to have frequent births. It itself placed women in a relatively shorter lifespan than men, despite biological criteria for longer life expectancy. At the same time, as more boys are born at birth than girls are born, the balance shifts in late adulthood, and more older women are observed in different societies; That is, a phenomenon that itself needs more support, care and supervision, in order to keep their quality of life at a satisfactory level following demographic change (growth).

Consequences of population aging
Today, compared to the early twentieth century, the world's elderly population, especially in industrialized countries, has almost quadrupled; For example, in 2012 the UK population aged 65 and over was estimated at more than 10 million, or 17% of the total population, while in 1901 the population was about 1.8 million or 4.7%. The total population is estimated. As far as Iran is concerned, the population / population ratio of 80 years and older between the 2006 and 2011 censuses has increased by about 42% (WPDS: 2012). Therefore, due to this aging process, the necessary policies and measures must always be adopted, so that their quality of life can be maintained at a satisfactory level. The results of population aging can be expressed as follows:

- Pensions and other additional benefits.

- More hospital care.

- More nursing homes.

- More in-house medical care and.

At the same time, as a result of such situations, families become more involved, families become more anxious, and ultimately more isolation and loneliness of the elderly leads to feelings of worthlessness in the elderly. Therefore, due to the ongoing demographic changes, the planning system should pay special attention to different population groups, especially the aging population.

Population change and quality of life mutually affect each other. People and policy-makers in developing world are doing their best to create the best of quality of life according to their standards in order to bring about better health and thereby longer life expectancy. Since 1950, many developing nations have tried to put plans into action to establish higher quality of life. In this way, they could raise many life standards, and more health, hygiene, education, more productivity, etc. However, the current densely populated world today, needs ever improving quality of life to compete with the increasing needs on the one hand, and declining natural resources on the other hand. Similarly, international interactions need comparative quality of life. The present era needs reformed quality of life to be able to interact and compete with higher quality of life nations. It is worth noting that developing nations with shortage of resources need to plan their population growth rate accordingly.