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Chapter 1 Chapter 1 Epidemiology Past and PresentEpidemiology Past and Present

Epidemiology: from Greek words:• epi, meaning “on or upon,”

•demos, meaning “people,” and

•logos, meaning “the study of.”

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“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.

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Basic DefinitionsBasic Definitions

Health: Health: a state of complete physical, a state of complete physical, mental, and social well-being and not mental, and social well-being and not merely the absence of disease (WHO, merely the absence of disease (WHO, 1948).1948).

Public HealthPublic Health: Organized community : Organized community effort to prevent disease and promote effort to prevent disease and promote health health

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Basic DefinitionsBasic Definitions

Illness:Illness: what a person physiologically or what a person physiologically or psychologically experiences.psychologically experiences.

Disease:Disease: a medically definable a medically definable physiological or psychological dysfunction.physiological or psychological dysfunction.

SicknessSickness: the state of dysfunction of the : the state of dysfunction of the social role of a person with disease. social role of a person with disease.

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Basic DefinitionsBasic Definitions

Morbidity:Morbidity: events and factors associated events and factors associated with disease or disability.with disease or disability.

Mortality:Mortality: related to death.related to death.

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Basic DefinitionsBasic Definitions

EndemicEndemic: disease and injuries occurring : disease and injuries occurring at a consistent rateat a consistent rate

Epidemic:Epidemic: the occurrence of disease or the occurrence of disease or injuries in clear excess of normalcy.injuries in clear excess of normalcy.

Pandemic:Pandemic: a epidemic that affects several a epidemic that affects several countries or continentscountries or continents

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Distribution. Distribution. Epidemiology is concerned Epidemiology is concerned with the frequency and pattern of health with the frequency and pattern of health events in a population. events in a population.

Frequency: Frequency: the number disease/injury the number disease/injury events in a population and the rate or risk events in a population and the rate or risk of disease in the population. of disease in the population. Rates Rates are are critical for making valid comparisons critical for making valid comparisons across different populations.across different populations.

Pattern: Pattern: the occurrence of health-related the occurrence of health-related events by events by time, placetime, place, and , and personal personal characteristicscharacteristics..

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Time: Time: includes annual occurrence, includes annual occurrence, seasonal occurrence, and daily or even seasonal occurrence, and daily or even hourly occurrence during an epidemic.hourly occurrence during an epidemic.

Place: Place: includes geographic variation, includes geographic variation, urban-rural differences, and location of urban-rural differences, and location of worksites or schools.worksites or schools.

Personal Personal characteristics include characteristics include demographic factors such as age, race, demographic factors such as age, race, sex, marital status, and socioeconomic sex, marital status, and socioeconomic status, as well as behaviors and status, as well as behaviors and environmental exposures.environmental exposures.

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Uses of EpidemiologyUses of Epidemiology1. Historical study 1. Historical study of the rise and fall of injuries of the rise and fall of injuries

and disease in a community. Can also produce and disease in a community. Can also produce projections. projections.

2. Population or community health diagnosis or 2. Population or community health diagnosis or assessment assessment (incidence, prevalence, etc.) (incidence, prevalence, etc.)

3. Study the workings of 3. Study the workings of health services health services (needs, (needs, resources, service analysis) resources, service analysis)

4. Estimate the 4. Estimate the individual’s chances or risks individual’s chances or risks for for injury and disease (age, race, behavior, etc.). injury and disease (age, race, behavior, etc.).

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Uses of EpidemiologyUses of Epidemiology

5.5. Completing the clinical picture (e.g., Completing the clinical picture (e.g., documentation of the numerous conditions that documentation of the numerous conditions that are associated with smoking).are associated with smoking).

66. . Identify syndromes Identify syndromes (A group of symptoms that (A group of symptoms that collectively indicate or characterize a disease, collectively indicate or characterize a disease, psychological disorder, or other abnormal psychological disorder, or other abnormal condition). condition).

7. Search for causes - 7. Search for causes - identifying factors which identifying factors which influence one’s risk of disease, so that influence one’s risk of disease, so that appropriate public health actions can be taken. appropriate public health actions can be taken. (For example, withdrawal of tainted food from (For example, withdrawal of tainted food from public consumption after epidemiology case public consumption after epidemiology case studies).studies).

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Epidemiologic TransitionsEpidemiologic Transitions

Epidemiologic transactions focus on Epidemiologic transactions focus on dramatic changes in morbidity and dramatic changes in morbidity and mortality in relation to:mortality in relation to: Demographic Demographic BiologicalBiological Socioeconomic factorsSocioeconomic factors

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Epidemiologic TransitionsEpidemiologic TransitionsChanges in 10 leading causes of death per 100,000Changes in 10 leading causes of death per 100,000

190019001. Pneumonia & Flu (202)1. Pneumonia & Flu (202)2. Tuberculosis (194)2. Tuberculosis (194)3. Diarrhea/gastrointest. (143)3. Diarrhea/gastrointest. (143)4. Heart disease (137)4. Heart disease (137)5. Inter-cranial lesions (107) 5. Inter-cranial lesions (107) 6. Nephritis (89)6. Nephritis (89)7. Accidents (72)7. Accidents (72)8. Cancer and tumors (64)8. Cancer and tumors (64)9. Senility (50)9. Senility (50)10. Diphtheria (40)10. Diphtheria (40)

20002000

1. Heart Disease (246)1. Heart Disease (246)

2. Malignant Neoplasms (194)2. Malignant Neoplasms (194)

3. Cerebrovascular Dis. (57)3. Cerebrovascular Dis. (57)

4. Lower Respiratory (43)4. Lower Respiratory (43)

5. Accidents (36)5. Accidents (36)

6. Diabetes (25)6. Diabetes (25)

7. Pneumonia & flu (22)7. Pneumonia & flu (22)

8. Alzheimer’s 198. Alzheimer’s 19

9. Nephritis (14)9. Nephritis (14)

10. Septicemia (11)10. Septicemia (11)

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Demographic TransitionsDemographic Transitions

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Demographic TransitionsDemographic Transitions

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Significant Historical Significant Historical ContributorsContributors

HippocratesHippocrates

John GrauntJohn Graunt

William FarrWilliam Farr

John SnowJohn Snow

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Hippocrates (circa 400 B.C.) attempted to Hippocrates (circa 400 B.C.) attempted to explain disease occurrence from a rational explain disease occurrence from a rational insteadinstead

of a supernatural viewpoint. In his essay entitled of a supernatural viewpoint. In his essay entitled “On Airs, Waters, and Places,” Hippocrates“On Airs, Waters, and Places,” Hippocrates

suggested that environmental and host factors suggested that environmental and host factors such as behaviors might influence thesuch as behaviors might influence the

development of disease.development of disease.

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John GrauntJohn Graunt landmark analysis of mortality data in 1662landmark analysis of mortality data in 1662 quantify patterns of birth, death, and disease occurrencequantify patterns of birth, death, and disease occurrence noting male-female disparities, high infant mortality, urban-rural noting male-female disparities, high infant mortality, urban-rural

differences, and seasonal variationsdifferences, and seasonal variations

William Farr 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 developed many of the basic practices used today in vital

statistics and disease classificationstatistics and disease classification extended the epidemiologic analysis of morbidity and mortality extended the epidemiologic analysis of morbidity and mortality

data, looking at the effects of marital status, occupation, and data, looking at the effects of marital status, occupation, and altitudealtitude

developed many epidemiologic concepts and techniques still in developed many epidemiologic concepts and techniques still in use today.use today.

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John Snow John Snow conducted studies of cholera conducted studies of cholera

outbreaks both to discover the outbreaks both to discover the cause of disease and to prevent its cause of disease and to prevent its recurrence. recurrence.

descriptive epidemiology from descriptive epidemiology from hypothesis generation to hypothesis generation to

classic study in 1854 classic study in 1854

2020

2121

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Early Epidemiological Early Epidemiological BeginningsBeginnings

Cholera Outbreak 1854Cholera Outbreak 1854Gathered dataGathered dataGenerated hypothesisGenerated hypothesisIntervenedIntervened

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

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DemographyDemography

DemographyDemography: The study of births, : The study of births, deaths, and migration and how they deaths, and migration and how they influence population changes.influence population changes.

The U.S. Census Bureau documents The U.S. Census Bureau documents population changes in the U.S.population changes in the U.S.

Population pyramids describe distribution Population pyramids describe distribution by age.by age.

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America at the Dawn of a America at the Dawn of a New CenturyNew Century

POPULATION POPULATION PROFILE OF THE PROFILE OF THE

UNITED STATES: 2000UNITED STATES: 2000

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Primary Data sources are: Primary Data sources are:

The Decennial Censuses of Population The Decennial Censuses of Population and Housing (Census 2000 and earlier and Housing (Census 2000 and earlier censuses)censuses)

The Current Population Survey (CPS), The Current Population Survey (CPS), andand

The Survey of Income and Program The Survey of Income and Program Participation (SIPP). Participation (SIPP).

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Every state grew during the 1990s, but DC lost population.

Source: U.S. Census Bureau, Census 2000 and 1990 census.

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In Census 2000, 75 percent of In Census 2000, 75 percent of respondents said they were White alone.respondents said they were White alone.

75.1%

12.3%

2.4%5.5%0.1%

3.6%0.9%

White alone

Black alone

American Indian andAlaska Native alone

Asian alone

Native Hawaiian andother Pacific IslanderaloneSome other race alone

Two or more races

Source: U.S. Census Bureau, Census 2000.

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Between 1990 and 2000, the population Between 1990 and 2000, the population aged 45 to 54 swelled 49 percent and those aged 45 to 54 swelled 49 percent and those

aged 85 and older grew 38 percent.aged 85 and older grew 38 percent.

12%7%

-8%

20%

49%

15%

2%

23%

38%

-20%-10%

0%10%20%30%40%50%60%

<15 15-24 25-34 35-44 45-54 55-64 65-74 75-84 85+

Percent Change 1990-2000

Source: U.S. Census Bureau, Census 2000 and 1990 census.

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Women outnumber men two to one in the Women outnumber men two to one in the group aged 85 and older.group aged 85 and older.

10598 95 91

8370

50

0

20

40

60

80

100

120

Under20

20 to44

45 to54

55 to64

65 to74

75 to84

85 andolder

(Number of men per 100 women by age)

Source: U.S. Census Bureau, Current Population Survey, March 2000.

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Almost one in five adults had some type of Almost one in five adults had some type of disability in 1997 and the likelihood of having disability in 1997 and the likelihood of having

a disability increased with age.a disability increased with age.

0%

20%

40%

60%

80%Anydisability

Severedisability

Needsassistance

Source: U.S. Census Bureau, Wave 5 (August - November 1997) of the 1996 Panel of the Survey of Income and Program Participation.

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Families still dominate American Families still dominate American households, but less so than they did 30 households, but less so than they did 30

years ago.years ago.

0% 20% 40% 60% 80% 100%

1970

2000

Family Households Nonfamily Households

MARRIEDWITHCHILDREN

MARRIEDNOCHILDREN

OTHERFAMILY

WOMENLIVING ALONE

MEN LIVINGALONE

OTHERNONFAMILY

Note: "Children" refers to children under age 18.

Source: U.S. Census Bureau, Current Population Surveys, March 1970 and 2000

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Epidemiologic TransitionsEpidemiologic TransitionsChanges in 10 leading causes of death per 100,000Changes in 10 leading causes of death per 100,000

190019001. Pneumonia & Flu (202)1. Pneumonia & Flu (202)2. Tuberculosis (194)2. Tuberculosis (194)3. Diarrhea/gastrointest. (143)3. Diarrhea/gastrointest. (143)4. Heart disease (137)4. Heart disease (137)5. Inter-cranial lesions (107) 5. Inter-cranial lesions (107) 6. Nephritis (89)6. Nephritis (89)7. Accidents (72)7. Accidents (72)8. Cancer and tumors (64)8. Cancer and tumors (64)9. Senility (50)9. Senility (50)10. Diphtheria (40)10. Diphtheria (40)

20002000

1. Heart Disease (246)1. Heart Disease (246)

2. Malignant Neoplasms (194)2. Malignant Neoplasms (194)

3. Cerebrovascular Dis. (57)3. Cerebrovascular Dis. (57)

4. Lower Respiratory (43)4. Lower Respiratory (43)

5. Accidents (36)5. Accidents (36)

6. Diabetes (25)6. Diabetes (25)

7. Pneumonia & flu (22)7. Pneumonia & flu (22)

8. Alzheimer’s 198. Alzheimer’s 19

9. Nephritis (14)9. Nephritis (14)

10. Septicemia (11)10. Septicemia (11)