1 Chapter 1 Epidemiology Past and Present Epidemiology: from Greek words: epi, meaning “on or upon,” demos, meaning “people,” and logos, meaning “the study of.”

2 “Epidemiology is the study of the distribution and determinants of health- related states or events in specified populations, and the application of this study to the control of health problems.” Study: Epidemiology is a scientific discipline, sometimes called “the basic science of public health.” It has, at its foundation, sound methods of scientific inquiry.

3 Basic Definitions Health: a state of complete physical, mental, and social well-being and not merely the absence of disease (WHO, 1948). Public Health: Organized community effort to prevent disease and promote health

4 Basic Definitions Illness: what a person physiologically or psychologically experiences. Disease: a medically definable physiological or psychological dysfunction. Sickness: the state of dysfunction of the social role of a person with disease.

5 Basic Definitions Morbidity: events and factors associated with disease or disability. Mortality: related to death.

6 Basic Definitions Endemic: disease and injuries occurring at a consistent rate Epidemic: the occurrence of disease or injuries in clear excess of normalcy. Pandemic: a epidemic that affects several countries or continents

7 Distribution. Epidemiology is concerned with the frequency and pattern of health events in a population. Frequency: the number disease/injury events in a population and the rate or risk of disease in the population. Rates are critical for making valid comparisons across different populations. Pattern: the occurrence of health-related events by time, place, and personal characteristics.

8 Time: includes annual occurrence, seasonal occurrence, and daily or even hourly occurrence during an epidemic. Place: includes geographic variation, urban-rural differences, and location of worksites or schools. Place: includes geographic variation, urban-rural differences, and location of worksites or schools. Personal characteristics include demographic factors such as age, race, sex, marital status, and socioeconomic status, as well as behaviors and environmental exposures.

9 Uses of Epidemiology 1. Historical study of the rise and fall of injuries and disease in a community. Can also produce projections. 2. Population or community health diagnosis or assessment (incidence, prevalence, etc.) 3. Study the workings of health services (needs, resources, service analysis) 4. Estimate the individual’s chances or risks for injury and disease (age, race, behavior, etc.).

10 Uses of Epidemiology 5.Completing the clinical picture (e.g., documentation of the numerous conditions that are associated with smoking). 6. Identify syndromes (A group of symptoms that collectively indicate or characterize a disease, psychological disorder, or other abnormal condition). 7. Search for causes - identifying factors which influence one’s risk of disease, so that appropriate public health actions can be taken. (For example, withdrawal of tainted food from public consumption after epidemiology case studies).

11 Epidemiologic Transitions Epidemiologic transactions focus on dramatic changes in morbidity and mortality in relation to: Demographic Demographic Biological Biological Socioeconomic factors Socioeconomic factors

12 Epidemiologic Transitions Changes in 10 leading causes of death per 100, Pneumonia & Flu (202) 2. Tuberculosis (194) 3. Diarrhea/gastrointest. (143) 4. Heart disease (137) 5. Inter-cranial lesions (107) 6. Nephritis (89) 7. Accidents (72) 8. Cancer and tumors (64) 9. Senility (50) 10. Diphtheria (40) Heart Disease (246) 2. Malignant Neoplasms (194) 3. Cerebrovascular Dis. (57) 4. Lower Respiratory (43) 5. Accidents (36) 6. Diabetes (25) 7. Pneumonia & flu (22) 8. Alzheimer’s Nephritis (14) 10. Septicemia (11)

13 Demographic Transitions

14 Demographic Transitions

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16 Significant Historical Contributors Hippocrates John Graunt William Farr John Snow

17 Hippocrates (circa 400 B.C.) attempted to explain disease occurrence from a rational instead of a supernatural viewpoint. In his essay entitled “On Airs, Waters, and Places,” Hippocrates suggested that environmental and host factors such as behaviors might influence the development of disease.

18 John Graunt landmark analysis of mortality data in 1662 landmark analysis of mortality data in 1662 quantify patterns of birth, death, and disease occurrence quantify patterns of birth, death, and disease occurrence noting male-female disparities, high infant mortality, urban-rural differences, and seasonal variations noting male-female disparities, high infant mortality, urban-rural differences, and seasonal variations William Farr systematically collect and analyze Britain’s mortality statistics. systematically collect and analyze Britain’s mortality statistics. developed many of the basic practices used today in vital statistics and disease classification developed many of the basic practices used today in vital statistics and disease classification extended the epidemiologic analysis of morbidity and mortality data, looking at the effects of marital status, occupation, and altitude extended the epidemiologic analysis of morbidity and mortality data, looking at the effects of marital status, occupation, and altitude developed many epidemiologic concepts and techniques still in use today. developed many epidemiologic concepts and techniques still in use today.

19 John Snow conducted studies of cholera outbreaks both to discover the cause of disease and to prevent its recurrence. conducted studies of cholera outbreaks both to discover the cause of disease and to prevent its recurrence. descriptive epidemiology from hypothesis generation to descriptive epidemiology from hypothesis generation to classic study in 1854 classic study in 1854

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22 Early Epidemiological Beginnings Cholera Outbreak 1854 Gathered data Generated hypothesis Intervened

23 What became of cholera? In the 20th Century, sanitary improvements have largely eliminated cholera from industrialized countries. Cholera remains endemic in many areas of the world, however. The seventh cholera pandemic that began in Indonesia in 1961 continues. After a Peruvian outbreak in 1991, Central and South America saw more than one million cases and eleven thousand deaths through 1995, and the disease also continues to produce significant morbidity and mortality in Africa and Asia.

24 Demography Demography: The study of births, deaths, and migration and how they influence population changes. The U.S. Census Bureau documents population changes in the U.S. Population pyramids describe distribution by age.

25 America at the Dawn of a New Century POPULATION PROFILE OF THE UNITED STATES: 2000

26 Primary Data sources are: The Decennial Censuses of Population and Housing (Census 2000 and earlier censuses) The Current Population Survey (CPS), and The Survey of Income and Program Participation (SIPP).

27 Every state grew during the 1990s, but DC lost population. Source: U.S. Census Bureau, Census 2000 and 1990 census.

28 In Census 2000, 75 percent of respondents said they were White alone. Source: U.S. Census Bureau, Census 2000.

29 Between 1990 and 2000, the population aged 45 to 54 swelled 49 percent and those aged 85 and older grew 38 percent. Source: U.S. Census Bureau, Census 2000 and 1990 census.

30 Women outnumber men two to one in the group aged 85 and older. (Number of men per 100 women by age) Source: U.S. Census Bureau, Current Population Survey, March 2000.

31 Almost one in five adults had some type of disability in 1997 and the likelihood of having a disability increased with age. Source: U.S. Census Bureau, Wave 5 (August - November 1997) of the 1996 Panel of the Survey of Income and Program Participation.

32 Families still dominate American households, but less so than they did 30 years ago. Source: U.S. Census Bureau, Current Population Surveys, March 1970 and 2000

33 Epidemiologic Transitions Changes in 10 leading causes of death per 100, Pneumonia & Flu (202) 2. Tuberculosis (194) 3. Diarrhea/gastrointest. (143) 4. Heart disease (137) 5. Inter-cranial lesions (107) 6. Nephritis (89) 7. Accidents (72) 8. Cancer and tumors (64) 9. Senility (50) 10. Diphtheria (40) Heart Disease (246) 2. Malignant Neoplasms (194) 3. Cerebrovascular Dis. (57) 4. Lower Respiratory (43) 5. Accidents (36) 6. Diabetes (25) 7. Pneumonia & flu (22) 8. Alzheimer’s Nephritis (14) 10. Septicemia (11)