Demographic Transition

Demographic transition is a term coined by F. W. Notestien in 1945 to describe the changes that occur in a population as it moves from a premodern to a modern society, or from a developing to an industrialized economy. Developing countries are characterized by a population in which there are high birth rates and high death rates. The age structure of the population is pyramidal and there are far more children than elderly. In the first stage of the demographic transition, as per capita income rises, death rates fall due to factors that may include improved hygiene, nutrition, and healthcare. Birth rates (fertility rates) remain high and there is rapid population growth. After some time, birth rates begin to decline as families decrease the number of children they wish to have. They invest more resources into fewer children and realize that most children will survive to adulthood. A new stable population state is eventually reached in which both birth and death rates are relatively low, and the age structure of the population is rectangular.

The epidemiologic transition that generally accompanies and contributes to the demographic transition involves a change in the patterns of health and disease in a population. Developing countries generally have high infant, child, and maternal mortality rates. In these countries, acute and infectious diseases such [Page 485]as pneumonia, tuberculosis, and meningitis are common causes of death. In industrial countries, infant, child, and maternal mortality tend to be relatively low, and cancer, heart disease, and stroke are the most common causes of death. These insidious and chronic diseases are often related to risk factors such as diet, smoking, and sedentary lifestyle. Cancers are a common cause of death in pre- and posttransition populations; however, the types of cancer vary. In developing countries, cancers are primarily those caused by mi-croorganisms—liver, cervical, stomach, and nasopharyngeal neoplasms. However, cancers of the developed world—lung, colon, and breast—may be related to the risk factors previously mentioned. Deaths from motor vehicle accidents generally increase during the early transition period as there are more motorized vehicles in operation, and decrease in the posttransition period as laws and technology improve the safety of vehicle operation.

There is a great deal of variability in how each country and/or population experiences the demographic and epidemiologic transitions based on political and social structure, and resources. There is also great debate as to whether economic growth or other social or external factors are primarily responsible for these changes. Emerging diseases, social upheaval, and other dramatic events can interrupt or reverse the transition processes. For example, the HIV epidemic and wars have stalled reductions in mortality in sub-Saharan Africa. Similarly, massive social and healthcare system disruption have moved countries of the former Soviet Union back into a state in which vaccine-preventable and infectious diseases are a significant cause of morbidity and mortality. The concepts of demographic and epidemiologic transition are critical to understanding the health needs and the determinants of health of a population. They are also useful in designing health interventions and for health infrastructure, human resource, and social infrastructure planning.

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