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Public health focuses on health issues in populations. Carrying out the mission of public health and achieving its goals, therefore, depend on the factors that change the size and characteristics of the population whose health is at stake.

The relationship between health and population dynamics, through the study of demography, guides the need for changes in public health practice. Changes in health influence vital events, including births, deaths, and divorce, in turn leading to population changes. Migration, the movement of people from place to place, is another demographic force that leads to new health issues and problems.

Four such issues illustrate the relationship between public health and population:

  1. Teenage pregnancy: Teenage pregnancy is a serious public health issue. It creates preventable health problems for both infant and mother. Teenage pregnancies are often unintended. In addition, they may interfere with education, personal development, and socioeconomic advancement for the young mother and father, and therefore the infant. In addition, teenage pregnancies have an important demographic impact on future generations.

  2. Aging: As the death rate declines in most parts of the world, life expectancy increases, and the number and ages of older people increase. Moreover, when low or declining fertility accompanies the decline in mortality, the proportion of older persons also increases and the median age of the population increases. The result for public health is that the spectrum of health problems and health-care needs become drastically different.

  3. Urbanization: In 1950, fewer than 30% of the world's population lived in cities. After the year 2000, more than 40% are residing in an urban area.1 Urbanization creates health problems related to the need for housing and sanitation, improved food supply, better urban transportation, and the redistribution of preventive and other health services.

  4. Refugees and other migrants: An estimated 19 million refugees, persons “of concern” to the United Nations High Commissioner for Refugees, are dispersed throughout the world.2 Refugees and other migrants may bring with them serious public health problems such as severe malnutrition and infections. In addition, their encampments may have unexpected levels of violence.

This chapter should enable a public health practitioner to carry out the following tasks:

  1. Identify useful sources of information about population and vital statistics

  2. Calculate basic measures of population change

  3. Identify determinants of population change

  4. Understand four contemporary critical issues related to population change


Data Sources

Population data are essential to defining and measuring public health problems and the groups of people in which they occur. Nonetheless, public health practitioners often find that, while the need for information of this kind is great, their knowledge of existing data sources prevents them from calculating the measurements required to evaluate public health problems. Census, regular national surveys, and vital registration statistics are the most fundamental ...

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