Epidemiological transition
In demography and medical geography, epidemiological transition is a phase of development witnessed by a sudden and stark increase in population growth rates brought about by medical innovation in disease or sickness therapy and treatment, followed by a re-leveling of population growth from subsequent declines in fertility rates. This theory was originally posited by Abdel R Omran in 1971.[1]
Theory
Omran divided the epidemiological transition of mortality into three phases, in the last of which chronic diseases replace infection as the primary cause of death.[2] These phases are:
- The Age of Pestilence and Famine: Where mortality is high and fluctuating, precluding sustained population growth, with low and variable life expectancy, vacillating between 20 and 40 years.
- The Age of Receding Pandemics: Where mortality progressively declines, with the rate of decline accelerating as epidemic peaks decrease in frequency. Average life expectancy increases steadily from about 30 to 50 years. Population growth is sustained and begins to be exponential.
- The Age of Degenerative and Man-Made Diseases: Mortality continues to decline and eventually approaches stability at a relatively low level. Life expectancy rises and exceeds 50 years, with fertility becoming the crucial factor in population growth.[1]
The epidemiological transition occurs as a country undergoes the process of modernization from developing nation to developed nation status. The developments of modern healthcare, and medicine like antibiotics, drastically reduces infant mortality rates and extends average life expectancy which, coupled with subsequent declines in fertility rates, reflects a transition to chronic and degenerative diseases as more important causes of death.
History
In general human history, Omran's first phase occurs when human population sustains cyclic, low-growth, and mostly linear, up-and-down patterns associated with wars, famine, epidemic outbreaks, as well as small golden ages, and localized periods of "prosperity". In early pre-agricultural history, infant mortality rates were high and average life expectancy low. Today, life expectancy in third world countries remains relatively low, as in many Sub-Saharan African nations where it typically doesn't exceed 60 years of age[3].
The second phase involves advancements in medicine and the devopment of a healthcare system. One treatment breakthrough of note was the discovery of penicillin in the mid 20th century which led to widespread and dramatic declines in death rates from previously serious diseases such as syphilis. Population growth rates surged in the 1950s, 1960s and 1970s, to 1.8% per year and higher, with the world gaining 2 billion people between 1950 and the 1980s alone.
Omran's third phase occurs when human birth rates drastically decline from highly positive replacement numbers to stable replacement rates. In several European nations replacement rates have even become negative.[4] As this transition generally represents the net effect of individual choices on family size (and the ability to implement those choices), it is more complicated. Omran gives three possible factors tending to encourage reduced fertility rates[1]:
- Biophysiologic factors, associated with reduced infant mortaliity and the expectation of longer life in parents,
- Socioeconomic factors, associated with childhood survival and the economic perceptions of large family size, and
- Psychologic or emotional factors, where society as a whole changes its rationale and opinion on family size and parental energies are redirected to qualitative aspects of child-raising.
This transition may also be associated with the sociological adaptations associated with demographic movements to urban areas, and a shift from agriculture and labor based production output to technological and service-sector-based economies.
Regardless, Chronic and degenerative diseases, and accidents and injuries, became more important causes of death. This shift in demographic and disease profiles is currently under way in most developing nations, however every country is unique in its transition speed based on a myriad of geographical and socio-political factors.
Further reading
- Casselli, Graziella; Mesle, France; & Vallin, Jacques (2002), "Epidemiologic transition theory exceptions", Genus: Journal of Population Sciences 9: 9–51, http://www.demogr.mpg.de/Papers/workshops/020619_paper40.pdf, retrieved 3 June 2010
- Fetter, Bruce; Coelho, Phillip R. P.; Rogers, John; Nelson, Marie C. (1997), "Forum: The Epidemiological Transition", Forum: The Health Transition Review (Health Transition Centre, National Centre for Epidemiology and Population Health, The Australian National University) 7, archived from the original on 2004, http://hdl.handle.net/1885/40188, retrieved 3 June 2010 . Contains three articles by four authors.
- Gribble, James N., & Preston, Samuel H (editors) (1993), The Epidemiological transition: policy and planning implications for developing countries, Washington, DC: National Academy Press, ISBN 0-309-04830-7, http://books.google.com.au/books?id=_EQrAAAAYAAJ&printsec=frontcover&dq=%22epidemiological+transition%22&lr=&as_drrb_is=q&as_minm_is=0&as_miny_is=&as_maxm_is=0&as_maxy_is=&as_brr=3&cd=1#v=onepage&q&f=false, retrieved 3 June 2010
- Xiaoyan Lei, Nina Yin, & Yaohui Zhao (April 2010), SES Health Gradients during the Epidemiological Transition: The Case of China, Discussion paper No. 4914, http://ftp.iza.org/dp4914.pdf, retrieved 3 June 2010
- C. G. N. Mascie-Taylor, Jean Peters, Stephen T. McGarvey (editors) (2004), The changing face of disease: implications for society, Florida: CRC Press, ISBN 0-415-32280-4, http://books.google.com.au/books?id=Xhk9cSQMxI0C&dq=%22changing+face+of+disease%22&printsec=frontcover&source=bn&hl=en&ei=vwQHTKDzLsbXcaqElZUO&sa=X&oi=book_result&ct=result&resnum=4&ved=0CDAQ6AEwAw#v=onepage&q&f=false, retrieved 3 June 2010
- McMichael, Anthony J; McKee, Martin; Shkolnikov, Vladimir; & Valkonen, Tapani (2004), "Mortality trends and setbacks: Global convergence or divergence?", Lancet 363: 1155–59, http://www.sage.wisc.edu/courses/400Patz/Mcmichaeletal.pdf, retrieved 3 June 2010
- Salomon, Joshua A., & Murray, Christopher J.L (2000), The Epidemiological Transition Revisited: New Compositional Models for Causes of Death by Age and Sex, The Global Burden of Disease 2000 in Aging Populations, Research paper No.01.17, http://www.hsph.harvard.edu/burdenofdisease/publications/papers/Epidemiological%20Transition%20Revisited.pdf, retrieved 3 June 2010
- Sanders, John W; Fuhrer, Greg S; Johnson, Mark D; & Riddle, Mark S (5 May 2008), "The epidemiological transition: the current status of infectious diseases in the developed world versus the developing world", Science Progress 91: 1–37, PMID 18453281, http://findarticles.com/p/articles/mi_go2834/is_1_91/ai_n29429522/?tag=content;col1, retrieved 3 June 2010
- Wahdan, M.H (1996), "The epidemiological transition", Eastern Mediterranean Health Journal 2 (1): 8–20, http://www.emro.who.int/publications/emhj/0201/02.htm, retrieved 3 June 2010
Notes
- ^ a b c Omran, A.R (2005. First published 1971), "The epidemiological transition: A theory of the epidemiology of population change", The Milbank Quarterly 83 (4): 731–57, http://www.milbank.org/quarterly/830418omran.pdf . Reprinted from The Milbank Memorial Fund Quarterly 49 (No.4, Pt.1), 1971, pp.509–538
- ^ Corruccini, Robert S., & Kaul, Samvit S (1983), "The epidemiological transition and the anthropology of minor chronic non-infectious diseases", Medical Anthropology 7: 36–50
- ^ CIA - The World Factbook -- Rank Order - Life expectancy at birth
- ^ Negative Population Growth About.com
See also