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Epidemiologic Transitions: The Past PUBHLTH 350 Matthew L. Boulton, MD, MPH September 28, 2015

Outline Classifying history by health The demographic transition The nutrition transition The epidemiologic transition

Omran’s “Ages” of Disease Social featuresDisease features Age of pestilence and famine Through 1650, traditional clan- and family-based society High mortality, young population, high rates of TB and smallpox Age of receding pandemics Further differentiation of classes but large family-based societies in rural areas Improved nutrition and sanitation, occupational health problems and accidents rise Age of degenerative and man-made diseases Small family sizes, women have careers, larger welfare spending Chronic disease, mental illness, pollution become more important Omran. Milbank Q. 1971

Some Definitions Demography: the study of the size and composition of human populations Epidemiology: the study of risk factors that determine the presence or absence of diseases and disorders (the distribution and determinants of disease) Statistics: –Birth rates: births per year per 1000 people in the total population –Fertility (fecundity): average number of children born to each woman Replacement: number of children needed to keep the population stable (2.1 in the United States) –Death rates = mortality rates: deaths per year per 1000 people in the total population –Age-adjusted rates: populations with different age structures can be compared Jacobsen. Global Health 2 nd Ed.

What are the Transitions? The demographic transition was first conceptualized to describe changes in society-specific birth rates and mortality rates over time Omran (1971) transferred these ideas to public health Transitions are a widely used concept in many fields: demography, medical anthropology, economics, and public health Researchers have articulated several different transitions: focus on the second transition Omran. Milbank Q. 1971

First TransitionEstablishment of agrarian societies Second Transition Industrialization Third Transition The future?

Demographic Transition A shift from higher to lower birth and death rates which occurs as populations or countries move from lower-income to higher-income economies Jacobsen. Global Health 2 nd Ed. Tijuana, Mexico San Diego, US

Demographic benchmarks Omran. Milbank Q. 1971

Pre 2 nd Transition2 nd TransitionPost 2 nd Transition High birth rate High death rate Stable population Declining death rate High birth rate Increasing population Reduced birth rate Reduced death rate Stable (or decreasing) population

Reprinted from U.S. Census Bureau, International Population Reports WP/02, Global Population Profile: Washington, DC: U.S. Government Printing Office; 2004, p. 35. from Skolnik. Global Health 101. Pre 2 nd TransitionDuring 2 nd TransitionPost 2 nd Transition High fertility High mortality Declining mortality High fertility Reduced fertility Reduced mortality Population Pyramids

What decreases fertility? Bio-physiologic factors: prolonged lactation, surviving infants mean the mother won’t quickly have another child Socioeconomic factors: the desirability of having many children decreases as more children survive, availability of birth control Psychological factors: rationale for many children decreases as more children survive, each child now provided better health care and education Omran. Milbank Q. 1971

Nutrition Transition A shift from challenges with population level under-nutrition to challenges with over-nutrition which occurs as populations or countries move from lower-income to higher- income economies Jacobsen. Global Health 2 nd Ed.

Diet after the Nutrition Transition Increased consumption of energy dense but nutrient dilute foods Food ≠ high-quality nourishment Increased prevalence of overweight

What causes the nutrition transition? Martorell

Epidemiologic Transition A shift from a high burden of illness and death due to infectious disease to a high burden of illness and death from chronic, non-communicable diseases (NCD) which occurs as populations move from lower income to higher- income economies All populations and countries have health issues, but the composition of those issues changes over time Jacobsen. Global Health 2 nd Ed.

Epidemiologic Transitions in the US in the 20 th Century Pre 2 nd Transition Leading causes of death in the U.S. in 1900 –Pneumonia (including influenza) –Tuberculosis –Diarrhea Post 2 nd Transition Leading causes of death in the U.S. since 1950 –Heart disease –Cancer –Stroke Jacobsen. Global Health 2 nd Ed.

20 th Century Control of Infectious Disease

10 Leading Causes of Death as a Percentage of All Deaths – United States, 1900 Source:

10 Leading Causes of Death as a Percentage of All Deaths – United States, 1997 Source:

Jacobsen. Global Health 2 nd Ed.

Which group(s) benefited the most from the epidemiologic transition? Childhood survival increases with fewer epidemics and increased nutrition and sanitation Females generally have better health outcomes than males, except during late adolescent and young adult ages Omran. Milbank Q. 1971

Death rates by age during 2 nd Transition Omran. Milbank Q. 1971

Improvement in death rate among young women Omran. Milbank Q. 1971

Transition models Classical (Western) modelE.g., Europe and North America Gradual transition from high mortality and high fertility to low fertility Occurred over many centuries Resulted initially from socioeconomic factors, later sanitation and medical factors Accelerated modelE.g., Japan Occurred only over several decades Resulted from sanitary and medical advances and national priorities Contemporary modelE.g., current developing countries Rapid changes in past half century Result from public health measures and national and international priorities Omran. Milbank Q. 1971

Questions of the Day Do national and international politics play a role in the epidemiologic transition? Do you agree with Omran that international medical packages accelerate the transition in developing countries?