EPIDEMIOLOGICAL TRANSITION: PREMISES, MODELS, PHASES - MEDICINE - 2025

The epidemiological transition is a theory that focuses its interest on the complex changes produced in health patterns and diseases. It analyzes their interactions, their determinants and the demographic, sociological and economic consequences.

Etymologically, the term epidemiology means the study of groups of people. It deals with analyzing how a disease is distributed, the mortality it causes, its causes and consequences in large population groups.

The epidemiological transition runs parallel to the demographic transition, which has as its main premise that mortality together with fertility are two fundamental factors that occur in the population's life dynamics.

The demographic transition and the epidemiological transition are interpretations of social phenomena that are used to describe a set of changes in the epidemiological and demographic patterns of a society.

These changes occur when a society goes from a situation of underdevelopment or industrial backwardness to a higher stage of development.

What is the epidemiological transition?

Before delving into details about the epidemiological transition, it is necessary to explain the etymological origin of the term epidemiology.

This Latin word is composed of three roots: epi, which means "on"; demos, whose meaning is "people"; and logos, which means "study"; that is, the study of people.

Epidemiology studies the distribution of a disease and its causes, the mortality that it causes and the consequences of this phenomenon in large population groups.

The theory of epidemiological transition bases its scientific interest on the changes that occur in the patterns of health and diseases of a population.

Similarly, it studies the interactions that are generated between these patterns, their causes and consequences from the demographic, sociological and economic point of view.

Likewise, this concept indicates the dynamism of the factors that intervene in the process, especially those related to diseases and mortality.

For example, there was a time when infectious diseases predominated due to lack of nutrition or access to clean water, and then eventually changed to conditions related to genetic and mental degeneration.

It is generated in parallel with the demographic transition, which is the change that occurs in populations that go from having high birth and mortality rates to low rates of these social phenomena.

To refer to the epidemiological transition, the concepts of health transition and mortality transition are also often used.

Theoretical premises

The epidemiological transition establishes five fundamental premises:

First premise

Mortality and fertility are two fundamental factors that occur in the life dynamics of the population.

Second premise

During the transition process, a long-term change in mortality and disease patterns is generated.

Infection pandemics are progressively displaced by human-caused degenerative diseases, which become the main form of morbidity and cause of death.

Third premise

The most significant changes in health and disease patterns during the epidemiological transition occur among children and young women. Both groups become the most benefited.

Fourth premise

Characteristic changes in health and disease patterns are closely linked to demographic and socioeconomic transitions, which are part of the modernization process.

Fifth premise

The characteristic variations in the pattern, the determinants, the rhythm, and the consequences of demographic change establish three differentiated basic models of the epidemiological transition: classical model, accelerated model, and contemporary or delayed model.

Omran Approach

In the middle of the 20th century, the need arises to understand population processes and the decline in the mortality rate in Europe in the past 200 years. The objective was to try to find the causes and reasons for such a situation.

Due to this, it was Abdel Omran who, in 1971, raised the theory of epidemiological transition to give him a clearer and more forceful answer to this particular phenomenon.

In the article called Epidemiological Transition, an epidemiological theory of population change, Omran exposes a series of postulates that indicate that humanity has gone through a series of stages, where mortality has been high until it is considerably reduced to the point where degenerative diseases they are now the main causes of death.

The author emphasizes that these patterns are part of a complex process where mortality plays a vital role in the dynamics of population growth.

However, they also have to do with elements such as economic, political, social and even technological development, which will also affect said index.

For Omran, it is important to highlight that the epidemiological transition meets essential phases:

• The Age of Pestilence and Famine: characterized by high and fluctuating mortality due to epidemics and wars. This affected population growth and resulted in a life expectancy of between 20 and 40 years.
• The Pandemic Era: mortality declines despite the presence of pandemics. Thanks to this, population growth begins to establish itself and life expectancy is established between 30 to 50 years.
• The Age of Degenerative Diseases: Mortality rates continue to decline so life expectancy exceeds 50 years. Fertility is the crucial factor for population growth.
• The Era of the Decline of Cardiovascular Mortality: added more recently, this is characterized by the treatment of cardiovascular diseases.
• The Era of Expected Quality of Life: at this stage, important numbers of longevity are expected, especially in the middle of this century.

Models of the epidemiological transition

It is important to mention a series of models that highlight the importance of the intervention of economic and social development in a society:

• Classic or Western model: it corresponds mainly to European societies where mortality and fertility rates have been reduced, thanks to an advanced socioeconomic system.
• Accelerated model: characteristic of the countries of Eastern Europe and Japan where they passed the Era of Pestilence and Famine quickly due to widespread sanitary improvements.
• Delayed Model: it occurs in the rest of the countries of the world where the decrease in mortality occurred after the Second World War. Although mortality decreases, fertility increases and the country, in addition, also has to deal with the problems of previous years.

Nutritional epidemiological transition

Among the fundamental elements for the decrease in mortality rates, is nutrition, which allows the survival of the inhabitants of a certain area.

In this way, eating habits and lifestyle will affect population growth and development, in what would be a complex demographic process.

Nutritional situations will vary by area. In Latin America, for example, there is a heterogeneous panorama where there are nations that show progress on the issue, but others have significant delays due to malnutrition problems presented in the past.

The same could be said of certain countries in Asia, where there has been an increase in the consumption of fats and sugars followed by a decrease in the consumption of cereals and fruits. Which also translates into a population with high levels of nutritional diseases and prone to degenerative diseases.

In more advanced societies –Europe and North America-, although there is progress in the health and fertility processes, they also present similar situations as the one mentioned in the Asian countries. That is, due to a diet with a high caloric profile, there is a greater presence of diseases related to obesity and overweight.

The intention of the nutritional epidemiological transition is to generate the appropriate policies to raise awareness in the population and encourage the consumption of a balanced diet in order to obtain a better quality of life.

Epidemiological transition in Mexico

In Latin America, the Epidemiological Transition was delayed compared to developed countries. It began after World War II, where these same nations also presented an advance towards the modern world.

Vaccines and actions aimed at health improvements stopped the advance of parasitic and infectious diseases in the mid-20th century.

In the case of Mexico, the main causes of death were due to illnesses such as influenza, pneumonia, whooping cough, smallpox and tuberculosis. It is even estimated that in the first two decades of the 20th century, these diseases caused 35% of deaths in the country.

After 1980, Mexico managed to improve the health system in addition to making other improvements in terms of access to food and medicine, as well as drinking water, which led to a 20% decrease in said index at the time.

Despite the previously mentioned advances, problems still persist where the most affected are the indigenous communities, which are unable to have access to the aforementioned.

The low presence of health and care units means that some rural Mexican areas present delays in the epidemiological transition at the national level.

It should be noted that, despite this panorama, the life expectancies currently registered have increased to yield an average of 75 years (for both men and women), which represents a significant improvement in terms of what was registered in the former decades of the last century.

Birth and death rates

The Mexican case contradicts the arguments that high birth rates are an obstacle to the economic or social development of a country. Also that economic and social development automatically produce a reduction in fertility.

As the Mexican case illustrates, the link between social change and declining birth rates is much more complex.

It is worth saying that progress is not necessarily accompanied by low birth rates or infant mortality.

The case of Mexico continues to be an enigma and a huge challenge for those who venture to present a simplistic vision between the epidemiological and demographic transition.

The decline in birth rates in Mexico since 1980 was less than expected and implied a growth in the population.

For this reason, it is recommended to study the real impact that economic growth has on education, health and work of the population.

It is also necessary to study the demographic and epidemiological impact on per capita income, productivity, educational services, and health.

Difference between epidemiological and demographic transition

The demographic transition tries to explain the reason for the growth of the world population in the last two centuries, and the link that exists between backwardness and fertility or development and lower birth rates.

Through this theory, the transformation process from pre-industrial or underdeveloped society with high birth and mortality rates to an industrial or developed society with low birth and mortality rates is described.

For its part, the epidemiological transition analyzes the processes of change in a dynamic and long-term way that occur in society, in terms of magnitude, frequency and distribution of mortality and morbidity in a specific population.

At the same time, the epidemiological transition seeks to explain the links between these changes and the economic, social and demographic transformations. It is not a single or isolated process.

References

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