Last updated Diagram showing sharp birth rate and death rate decreases between Time 1 and Time 4, the congruent increase in population caused by delayed birth rate decreases, and the subsequent re-leveling of population growth by Time 5.
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.[6] These phases are:
The Age of Pestilence and Famine: Mortality is high and fluctuating, precluding sustained population growth, with low and variable life expectancy vacillating between 20 and 40 years. It is characterized by an increase in infectious diseases, malnutrition and famine, common during the Neolithic age. Before the first transition, the hominid ancestors were hunter-gatherers and foragers, a lifestyle partly enabled by a small and dispersed population. However, unreliable and seasonal food sources put communities at risk for periods of malnutrition.
The Age of Receding Pandemics: 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. Mortality is increasingly related to degenerative diseases, cardiovascular disease (CVD), cancer, violence, accidents, and substance abuse, some of these due primarily to human behavior patterns. The average life expectancy at birth rises gradually until it exceeds 50 years. It is during this stage that fertility becomes the crucial factor in population growth.
In 1998 Barrett et al.[7] proposed two additional phases in which cardiovascular diseases diminish as a cause of mortality due to changes in culture, lifestyle and diet, and diseases associated with aging increase in prevalence. In the final phase, disease is largely controlled for those with access to education and health care, but inequalities persist.
The Age of Declining CVD Mortality, Aging and Emerging Diseases: Technological advances in medicine stabilize mortality and the birth rate levels off. Emerging diseases become increasingly lethal due to antibiotic resistance, new pathogens like Ebola or Zika, and mutations that allow old pathogens to overcome human immunity.
The Age of Aspired Quality of Life with Persistent Inequalities: The birth rate declines as lifespan is extended, leading to an age-balanced population. Socioeconomic, ethnic, and gender inequalities continue to manifest differences in mortality and fertility.
The epidemiological transition occurs when a country undergoes the process of transitioning from developing nation to developed nation status. The developments of modern healthcare and medicine, such as antibiotics, drastically reduce infant mortality rates and extend 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.
The theory of epidemiological transition uses patterns of health and disease as well as their forms of demographic, economical and sociological determinants and outcomes.[4]
History
Population pyramids of developed and developing nations, showing how increased lifespan and changes in fertility alter the population. Each bar represents an age category and its percent of the total population, with males to the left and females to the right.
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 developing countries remains relatively low, as in many Sub-Saharan African nations where it typically doesn't exceed 60 years of age.[8]
The second phase involves improved nutrition as a result of stable food production along with advances in medicine and the development of health care systems. Mortality in Western Europe and North America was halved during the 19th century due to closed sewage systems and clean water provided by public utilities, with a particular benefit for children of both sexes and to females in the adolescent and reproductive age periods, probably because the susceptibility of these groups to infectious and deficiency diseases is relatively high.[9][10] An overall reduction in malnutrition enabled populations to better resist infectious disease. Treatment breakthroughs of importance included the initiation of vaccination during the early nineteenth century, and the discovery of penicillin in the mid 20th century, which led respectively to a widespread and dramatic decline in death rates from previously serious diseases such as smallpox and sepsis. Population growth rates surged in the 1950s, 1960's and 1970's to 1.8% per year and higher, with the world gaining 2 billion people between 1950 and the 1980s.[citation needed] A decline in mortality without a corresponding decline in fertility leads to a population pyramid assuming the shape of a bullet or a barrel, as young and middle-age groups comprise equivalent percentages of the population.[citation needed]
Omran's third phase occurs when human birth rates drastically decline from highly positive replacement rates to stable replacement numbers. In several European nations replacement rates have even become negative.[11] This transition generally represents the net effect of individual choices on family size and the ability to implement those choices. Omran gives three possible factors tending to encourage reduced fertility rates:[4]
Bio-physiologic factors, associated with reduced infant mortality and the expectation of longer life in parents;
Socioeconomic factors, associated with childhood survival and the economic challenges of large family size; and
Psychological 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.
Impact on fertility
Improvements in female and childhood survival that occur with the shift in health and disease patterns discussed above have distinct and seemingly contradictory effects on fertility. While better health and greater longevity enjoyed by females of reproductive age tend to enhance fertility, the reduced risks to infants and young children that occurs in the later stages of the transition tends to have the opposite effect: prolonged breastfeeding associated with reduced mortality among infants and toddlers, together with parental recognition of improved childhood survival, tend to lengthen birth intervals and depress overall reproductive rates.[4]
Economic impact
The transition may also be associated with demographic movements to urban areas, and a shift from agriculture and labor-based production output to technological and service-sector-based economies. This shift in demographic and disease profiles is currently under way in most developing nations, however every country is unique and transition speed is based on numerous geographical and sociopolitical factors. Whether the transition is due to socioeconomic improvements (as in developed countries) or by modern public health programs (as has been the case in many developing countries), the lowering of mortality and of infectious disease tends to increase economic productivity through better functioning of adult members of the labor force and through an increase in the proportion of children who survive and mature into productive members of society.[4]
Models of transition
Demographic change in Germany, Sweden, Chile, Mauritius, China from 1820 to 2010. Pink line: crude death rate (CDR), green line: (crude) birth rate (CBR), yellow line: population.
Omran developed three models to explain the epidemiological transition.[4]
Classical/Western model: (England, Wales, and Sweden) Countries in Western Europe typically experienced a transition that began in the late eighteenth century and lasted over 150 years to the post-World War II era. The lengthy transition allowed fertility to decline at virtually the same rate that mortality also declined. Germany might be considered another example of this model.
Accelerated model: (Japan) Japan experienced a rapid transition as a result of a few decades of intensive war-driven industrialization followed by postwar occupation. The accelerated transition follows a pattern similar to the Classical/Western Model except that it occurs within a much shorter time span. China might be considered another example of this model.
Contemporary/Delayed model: (Chile, Ceylon) Due to slow economic development, Chile and Ceylon (Sri Lanka) experienced delayed transitions that have lasted into the 21st century. Medical and public health improvements have reduced mortality, while the birth rate remains high. Cultural traditions combined with political and economic instability and food insecurity mean that mortality for women and children fluctuates more than for men. Mauritius might be considered another example of this model.
Determinants of disease
Ecobiological: changing patterns of immunity, vectors (such as the black rat partially responsible for spreading bubonic plague in Europe), and the movement of pathogenic organisms. These alter the frequency of epidemic infectious diseases as well as chronic infections and other illnesses that affect fertility and infant mortality.
Socioeconomic: political and cultural determinants, including standards of living, health habits, hygiene and nutrition. Hygiene and nutrition are included here, rather than under medical determinants, because their improvement in western countries was largely a byproduct of social change rather than a result of medical design.
Medical/Public health: specific preventive and curative measures used to combat disease, including improved public sanitation, immunization and the development of decisive therapies. Medical and public health factors came into play late in the western transition, but have an influence early in certain accelerated and contemporary transitions.[4]
Other perspectives
Leading causes of DALYs and percentage change between 1990 and 2013, Chile
McMichael, Preston, and Murray offer a more nuanced view of the epidemiological transition, highlighting macro trends and emphasizing that there is a change from infectious to non-communicable disease, but arguing that it happens differently in different contexts.[citation needed]
One of the first to refine the idea of the epidemiological transition was Preston, who in 1976 proposed the first comprehensive statistical model relating mortality and cause-specific mortality. Preston used life tables from 43 national populations, including both developed countries such as United States and England and developing countries such as Chile, Colombia, Costa Rica, Guatemala, México, Panama, Taiwan, Trinidad and Tobago, and Venezuela. He used multiple linear regression to analyze the cause-specific-age-standardized death rates by sex. The estimated slopes represented the proportional contribution of each cause to a unit change in the total mortality rate. With the exception of neoplasms in both sexes and cardiovascular disease in males, all of the estimated slopes were positive and statistically significant. This demonstrated that the mortality rates from each specific cause were expected to decline as total mortality declined. The major causes accounting for the decline were all infectious and parasitic diseases.[12]
McMichael et al. argue (2004) that the epidemiological transition has not taken place homogeneously in all countries. Countries have varied in the speed with which they go through the transition as well as what stage of the transition they are in. The global burden of disease website provides visual comparisons of the disease burdens of countries and the changes over time.[citation needed] The epidemiological transition correlates with changes in life expectancy. Worldwide, mortality rates have decreased as both technological and medical advancements have led to a tremendous decrease in infectious diseases. With fewer people dying from infectious diseases, there is a rising prevalence of chronic and/or degenerative diseases in the older surviving population.[citation needed]
McMichael et al. describe life expectancy trends as grouped into three categories, as suggested by Casselli et al.:
Rapid gains among countries such as Chile, Mexico and Tunisia that have strong economic and technical relationships with developed countries
Slower plateauing gains mostly among developed countries with slower increases in life expectancy (for example, France)
Frank reversals occurring mostly in developing countries where the HIV epidemic led to a significant decline in life expectancy, and countries in the former Soviet Union, afflicted by social upheavals, heavy alcohol consumption and institutional inadequacy (for example, Zimbabwe and Botswana)[13]
Leading causes of DALYs and percentage change between 1990 and 2013, FranceLeading causes of DALYs and percentage change between 1990 and 2013, Zimbabwe
Murray and Lopez (1996) offered one of the most important cause-of-death models as part of the 1990 Global Burden of Disease Study. Their "cause of death" patterns sought to describe the fraction of deaths attributed to a set of mutually exclusive and collectively exhaustive causes. They divided diseases into three cause groups and made several important observations:
Group 1 - communicable, maternal, perinatal, and nutritional: These causes of death decline much faster than overall mortality and comprise a small fraction of deaths in wealthier countries.
Group 2 - non-communicable diseases: These causes of death are a major challenge for countries that have completed or nearly completed the epidemiological transition.
Group 3 - injuries: This cause of death is most variable within and across different countries and is less predictive of all-cause mortality.
The regression approach underlying the Global Burden of Disease received some critique in light of real-world violations of the model's "mutually exclusive and collectively exhaustive" cause attribution.[14]
Building on the existing body of evidence, Salomon and Murray (2002), further add nuances to the traditional theory of epidemiological transition by disintegrating it based on disease categories and different age-sex groups, positing that the epidemiological transition entails a real transition in the cause composition of age-specific mortality, as opposed to just a transition in the age structure. Using Global Burden of Disease data from 1990, they disintegrate the transition across three cause groups: communicable diseases, non-communicable diseases and injuries, seeking to explain the variation in all-cause mortality as a function of cause-specific mortality in 58 countries from 1950 to 1998. This analysis validates the underlying premise of the classic epidemiological transition theory: as total mortality declines and income rises, communicable diseases cause less and less mortality compared to non-communicable diseases and injuries. Decomposing this overall impact by age-sex groups, they find that for males, when overall mortality decreases, the importance of non-communicable diseases (NCDs) increases relative to the other causes with an age-specific impact on the role of injuries, whereas for women, both NCDs and injuries gain a more significant share with mortality decreases. For children over one year, they find that there is a gradual transition from communicable to non-communicable diseases, with injuries remaining significant in males. For young adults, the epidemiological transition is particularly different: for males, there is a shift from injuries to NCDs in lower income settings, and the opposite in higher-income settings; for females, rising income also signifies a shift from NCDs to injuries, but the role of injuries becomes more significant over time compared to males. Finally, for both males and females over 50, there is no epidemiological transition impact on the cause composition of mortality.[14]
Current evidence
The majority of the literature on the epidemiological transition that was published since these seminal papers confirms the context-specific nature of the epidemiological transition: while there is an overall all-cause mortality decline, the nature of cause-specific mortality declines differs across contexts. Increasing obesity rates in high-income countries are further confirming the epidemiological transition theory as the epidemic leads to an increase in NCDs. The picture is more nuanced in low- and middle-income countries, where there are signs of a protracted transition with the double burden of communicable and noncommunicable disease. A recent review of cause-specific mortality rates from 12 low- and middle-income countries in Asia and sub-Saharan Africa by Santosa and Byass (2016) shows that broadly, low- and middle-income countries are rapidly transitioning to lower total mortality and lower infectious disease mortality.[14] A more macro-level analysis from the Global Burden of Disease data conducted by Murray and others (2015) finds that while there is a global trend towards decreasing mortality and increasing NCD prevalence, this global trend is being driven by country-specific effects as opposed to a broader transition; further, there are varying patterns within and between countries, which makes it difficult to have a single unified theory of epidemiological transition.[15]
A theory of epidemiological transition aimed at explaining not just describing changes in population disease and mortality profiles would need to encompass the role in different morbid conditions of infectious diseases contracted over the life course. The concept of linear transition from infectious diseases to other conditions referred to as degenerative or non-communicable, was based on a false dichotomy as common microorganisms have now been confirmed as causal agents in several conditions recorded as the underlying cause of many deaths. A revised transition model might focus more on disease aetiology and the determinants of cause-specific mortality change, while encompassing the possibility that infectious causation may be established for other morbid conditions through the vast amount of ongoing research into associations with infectious diseases.[16][17]
↑ Mauck, Aaron Pascal. "Managing Care: History of Diabetes in the Twentieth Century". UMI Dissertations. ProQuest612814971.{{cite web}}: Missing or empty |url= (help)
↑ Porta, Miquel (2014). A dictionary of epidemiology (Sixthed.). Oxford University Press. ISBN9780199976737.
↑ Corruccini, Robert S. & Kaul, Samvit S (1983), "The epidemiological transition and the anthropology of minor chronic non-infectious diseases", Medical Anthropology, 7 (3): 36–50, doi:10.1080/01459740.1983.9987039
↑ Barrett, Ronald; Kuzawa, Christopher W; McDade, Thomas; Armelagos, George J (1998), "EMERGING AND RE-EMERGING INFECTIOUS DISEASES: The Third Epidemiologic Transition", Annual Review of Anthropology, 27: 247–271, doi:10.1146/annurev.anthro.27.1.247, S2CID2792275
Fetter, Bruce; Coelho, Phillip R. P.; Rogers, John; Nelson, Marie C. (1997), "Forum: The Epidemiological Transition"(PDF), Forum: The Health Transition Review, 7, hdl:1885/40188, archived from the original(PDF) on 2009-10-14, retrieved 2010-06-03. Contains three articles by four authors.
In demography, demographic transition is a phenomenon and theory which refers to the historical shift from high birth rates and high death rates in societies with minimal technology, education and economic development, to low birth rates and low death rates in societies with advanced technology, education and economic development, as well as the stages between these two scenarios. In economic growth, the demographic transition has swept the world over the past two centuries, and the unprecedented population growth of the post-Malthusian period was reversed, reducing birth rates and population growth significantly in all regions of the world, and enabling economies to translate more of the gains of factor accumulation and technological progress into per capita income growth. The demographic transition strengthens economic growth process by three changes: (i) reduced dilution of capital and land stock, (ii) increased investment in human capital, and (iii) increased size of the labor force relative to the total population and changed age population distribution. Although this shift has occurred in many industrialized countries, the theory and model are frequently imprecise when applied to individual countries due to specific social, political and economic factors affecting particular populations.
India's population in 2021 as per World Bank is 1.39 billion. Being the world's second-most-populous country and one of its fastest-growing economies, India experiences both challenges and opportunities in context of public health. India is a hub for pharmaceutical and biotechnology industries; world-class scientists, clinical trials and hospitals yet country faces daunting public health challenges like child undernutrition, high rates of neonatal and maternal mortality, growth in noncommunicable diseases, high rates of road traffic accidents and other health related issues.
The Global Burden of Disease Study (GBD) is a comprehensive regional and global research program of disease burden that assesses mortality and disability from major diseases, injuries, and risk factors. GBD is a collaboration of over 3600 researchers from 145 countries. Under principal investigator Christopher J.L. Murray, GBD is based in the Institute for Health Metrics and Evaluation (IHME) at the University of Washington and funded by the Bill and Melinda Gates Foundation.
A non-communicable disease (NCD) is a disease that is not transmissible directly from one person to another. NCDs include Parkinson's disease, autoimmune diseases, strokes, most heart diseases, most cancers, diabetes, chronic kidney disease, osteoarthritis, osteoporosis, Alzheimer's disease, cataracts, and others. NCDs may be chronic or acute. Most are non-infectious, although there are some non-communicable infectious diseases, such as parasitic diseases in which the parasite's life cycle does not include direct host-to-host transmission.
Malaysia is classified by The World Bank as upper middle income country and is attempting to achieve high-income status by 2020 and to move further up the value-added production chain by attracting investments in high technology, knowledge-based industries and services. Malaysia's HDI value for 2015 was recorded at 0.789 and HDI rank no 59 out of 188 countries and territories on the United Nations Development Programme's Human Development Index. In 2016, the population of Malaysia is 31 million; Total expenditure on health per capita is 1040; Total expenditure on health as % of GDP (2014) was 4.2 Gross national income (GNI) per capita was recorded at 24,620
Nutrition transition is the shift in dietary consumption and energy expenditure that coincides with economic, demographic, and epidemiological changes. Specifically the term is used for the transition of developing countries from traditional diets high in cereal and fiber to more Western-pattern diets high in sugars, fat, and animal-source food.
Health in Ethiopia has improved markedly since the early 2000s, with government leadership playing a key role in mobilizing resources and ensuring that they are used effectively. A central feature of the sector is the priority given to the Health Extension Programme, which delivers cost-effective basic services that enhance equity and provide care to millions of women, men and children. The development and delivery of the Health Extension Program, and its lasting success, is an example of how a low-income country can still improve access to health services with creativity and dedication.
The Tajikistan health system is influenced by the former Soviet legacy. It is ranked as the poorest country within the WHO European region, including the lowest total health expenditure per capita. Tajikistan is ranked 129th as Human Development Index of 188 countries, with an Index of 0.627 in 2016. In 2016, the SDG Index value was 56. In Tajikistan health indicators such as infant and maternal mortality rates are among the highest of the former Soviet republics. In the post-Soviet era, life expectancy has decreased because of poor nutrition, polluted water supplies, and increased incidence of cholera, malaria, tuberculosis, and typhoid. Because the health care system has deteriorated badly and receives insufficient funding and because sanitation and water supply systems are in declining condition, Tajikistan has a high risk of epidemic disease.
Niger is a landlocked country located in West Africa and has Libya, Chad, Nigeria, Benin, Mali, Burkina Faso, and Algeria as its neighboring countries. Niger was French territory that got its independence in 1960 and its official language is French. Niger has an area of 1.267 million square kilometres, nevertheless, 80% of its land area spreads through the Sahara Desert.
The current population of Myanmar is 54.05 million. It was 27.27 million in 1970. The general state of healthcare in Myanmar is poor. The military government of 1962-2011 spent anywhere from 0.5% to 3% of the country's GDP on healthcare. Healthcare in Myanmar is consistently ranked among the lowest in the world. In 2015, in congruence with a new democratic government, a series of healthcare reforms were enacted. In 2017, the reformed government spent 5.2% of GDP on healthcare expenditures. Health indicators have begun to improve as spending continues to increase. Patients continue to pay the majority of healthcare costs out of pocket. Although, out of pocket costs were reduced from 85% to 62% from 2014 to 2015. They continue to drop annually. The global average of healthcare costs paid out of pocket is 32%. Both public and private hospitals are understaffed due to a national shortage of doctors and nurses. Public hospitals lack many of the basic facilities and equipment. WHO consistently ranks Myanmar among the worst nations in healthcare.
According to the World Bank income level classification, Portugal is considered to be a high income country. Its population was of 10,283,822 people, by 1 July 2019. WHO estimates that 21.7% of the population is 65 or more years of age (2018), a proportion that is higher than the estimates for the WHO European Region.
The Republic of Moldova has a universal health care system.
Malawi ranks 170th out of 174 in the World Health Organization lifespan tables; 88% of the population live on less than £2.40 per day; and 50% are below the poverty line.
Zambia is a landlocked country in Sub Saharan Africa which experiences a burden of both communicable and non-communicable diseases. In line with WHO agenda for equity in health, it has adopted the Universal Health Coverage agenda to mitigate the challenges faced within the health sector. The Ministry of Health (MOH) provides information pertaining to Zambian health. The main focus of the Ministry of Health has been provision of uninterrupted care with emphasis on health systems strengthening and services via the primary health care approach.
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In reproductive health, obstetric transition is a concept around the secular trend of countries gradually shifting from a pattern of high maternal mortality to low maternal mortality, from direct obstetric causes of maternal mortality to indirect causes, aging of maternal population, and moving from the natural history of pregnancy and childbirth to institutionalization of maternity care, medicalization and over medicalization. This concept was originally proposed in the Latin American Association of Reproductive Health Researchers in analogy of the epidemiological, demographic and nutritional transitions.
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Environmental risk transition is the process by which traditional communities with associated environmental health issues become more economically developed and experience new health issues. In traditional or economically undeveloped regions, humans often suffer and die from infectious diseases or of malnutrition due to poor food, water, and air quality. As economic development occurs, these environmental issues are reduced or solved, and others begin to arise. There is a shift in the character of these environmental changes, and as a result, a shift in causes of death and disease.
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