"The theory of epidemiologic transition focuses on the complex change in patterns of health and disease and on the interaction between these patterns and their demographic economic and sociologic determinants and consequences" Discuss

INTRODUCTION.
Etymologically epidemiology is a combination of three Greeks words epi- means upon, demos-means people and logos mean study. Epidemiology is the study of what comes upon’ a group of people. More specifically epidemiology is concern with the distribution of diseases and heath and with their determinants and consequences in population groups.

According to Darwin (2011: 98). Epidemiology refers to the study of incidence, distribution and control of an epidemic disease in a population. It is a field of study that concern with the heath and diseases in population.

Sukon & Marie, PhD(2008) defines Epidemiology as the study of the distribution and determinants of health, disease, or injury in human populations and the application of this study to the control of health problems.

Robert E. (1996:668). The epidemiologic transition describes changing patterns of population age distributions, mortality, fertility, life expectancy, and causes of death. A number of critiques of the theory have revealed limitations, including an insufficient account of the role of poverty in determining disease risk and mortality, a failure to distinguish adequately the risk of dying from a given cause or set of causes from the relative contributions of various causes of death to overall mortality, and oversimplification of the transition patterns, which do not fit neatly into either historical periods or geographic locations. Recent developments in epidemiologic methods reveal other limitations. A life course perspective prompts examination of changes in causal pathways across the life span when considering shifts in the age distribution of a population as described by the epidemiologic transition theory. The ecological model assumes multiple levels of determinants acting in complex and interrelated ways, with higher level determinants exhibiting emergent properties. Development, testing, and implementation of innovative approaches to reduce the risks associated with the sedentary lifestyle and hyper nutrition in developed countries should not overshadow the continuing threat from infectious diseases, especially resistant strains or newly encountered agents. Interventions must fit populations and the threats to health they experience, while anticipating changes that will emerge with success in some areas. This will require new ways of thinking that go beyond the epidemiologic transition theory.

Epidemiologic transition raises the question of transition from what to what? There are two major components of the transition such as changes in population growth trajectories and composition, especially in the age distribution from younger to older, and  changes in patterns of mortality, including increasing life expectancy and reordering of the relative importance of different causes of death.

Though the ideas of Omran is typically credited with formulating the theory of the epidemiologic transition in the form that came to be frequently cited. In his 1971 article1 he wrote: “Conceptually, the theory of epidemiologic transition focuses on the complex change in patterns of health and disease and on the interactions between these patterns and their demographic, economic and sociologic determinants and consequences.” Since the 1971 publication the theory has been adopted , revised and criticized, demonstrating both its influence and limitations. The theory is most relevant as a way of looking at and understanding the relation among disease, mortality patterns, and population dynamics rather than as a definitive explanation or prediction.

This theory describes changing patterns of population distributions in relation to changing patterns of mortality, fertility, life expectancy, and leading causes of death. The perspective has its origins in demography, but finds a compatible conceptual home in public health and epidemiology in particular. The concept, with historical and recent data is obtained from the United States and other countries to illustrate key ideas.

The theory of epidemiologic transition has been useful in laying out an overarching perspective on changing demographic patterns. The various criticisms of the theory suggest it is most relevant as a way of looking at and understanding the relation among disease, mortality patterns, and population rather than as a definitive explanation or prediction. Among the major critiques of the theory is that the overemphasis on mortality rather than disease causality and morbidity misses critical pieces of complex phenomena. The focus on mortality and life expectancy gives insufficient attention to disability and quality of life

The theory of epidemiological transition theory uses patterns of heath and disease as well as their forms of demographic, economical and sociological approach of population interaction of the causes and effects of population change as follows

Life expectancy ,this is the number of years that an average  person  born in a given area may expected to live or the average age at which people die, in the epidemiological transition theory,  the life expectancy increase  through the increase and improve of health service that help in cure by antibiotic of various infection disease that attack people in both  chronic and manmade disease as a result in treatment  of different disease that attack people in population hence increase in population through  good health service also in lack of health facilities service in  for example in rural area there is short life expectancy due to lack of skilled people concerning health service and medical care of disease  also lack of health  service such as  school and hospital as a result of short life expectancy.
Mortality this the factor for complex change in population, that is the occurrence of death in population that is cause complex change through disease where by  people death  for examples, there are diseases like Malaria and Typhoid, that are  infection diseases to people as a result for complex change in population also it generative diseases and led to increase complex change in population for example diseases such as  brain disease, heart disease , bone disease and macro disease that are manmade disease like AIDS  that will cause infection to the people as a result to the increase of death, area with low infection disease population is high , compare to area with high infection disease like Africa that cause high mortality.

Distribution, in population distribution refers to the way in which people are spread out across the earth surface; also it can be occurrence or non occurrence of people in a certain geographical area.  Distribution is uneven and changes over period of time , In epidemiological transition theory distribution occur due to availability of health and disease patterns for example in area which has good health care for example hospital for treatment of infection disease  and school for provision of education concerning life style and measures to escape  infection disease for example AIDS is high in a place due to the lack of knowledge concerning that disease as a result for high death, therefore area with good health service is high in number  due to good health service for example China is high in number of people due to good  social service compare to area where there is lack o social serve as a result for distribution of people in population.

Economical, this factor increase the variability of food as well as improve heath to the people through availability of food and surprise of good led to have good heath, hence their reproductive increase also in other hand there is lack of food due to the laziness of the people in economic activity or due to the climatic change that led to the occurrence of famine.

Sociological factor, this factor involve the interaction of that can led the eruption of diseases such as TB due to the high number of people for instance in urban, people are easy to be affected from this disease compared to rural area. This is due to the availability of interaction of the large number of people

Fertility and birth rate, this is the factor that influence population change which occur through improvement in health and medical services and percentage of women married at youngest age for example Sub Saharan, Asia then in Northern Africa hence increase in fertility rates also increase the rate of birth as a result for increase in of population through good social service for treatment of infection or disease.

CONCLUSION
In generally, according to the theory that explained by Omran, it is true that the theory of epidemiologic transition focuses on the complex change in pattern of heath and disease on the interaction between this pattern and demographic economic and sociological determinant and consequences, and also heath and disease influencing the change of pattern and demographic. In economic situation the increase of mortality rate will affect the development of a place. Therefore, the theory outlined the following thing in summary
⦁ Mortality and population dynamic.
⦁ Mortality and disease patterns.
⦁ Medical and public health determinants.
⦁ Interacting transition variables.
⦁ Mortality age and sex.










REFERENCES
Armelagos GJ, Brown PJ, Turner B. (2005). Evolutionary, historical and political economic
perspectives on health and disease. United states: oxford university.

Omran, A.R.(1971) "The Epidemiological Transition: A Theory of the Epidemiology of
Population Change." The Milbank Memorial Fund Quarterly.

Sukon,K & Marie,D PhD(2008). Biostatistics and Epidemiology within the Paradigm of Public
Health. Johns Hopkins University

Susser E, Robert E. (1996) The Epidemiological Transition: A Theory of the Epidemiology of
Population Change.United states: The Milbank Memorial Fund Quarterly.