Midterm Review Flashcards
1 Contrast between PH with medicine
Ph focuses on prevention
– Achievements may be more difficult to recognize
– Less attention and funding
– Less than 5% of U.S. health spending is on public health
- Yet public health programs clearly save lives and medical costs
– U.S. life expectancy ↑ by ~30 years over 20th cent
– Only ~5 of the 30 years can be attributed to medical care
– Public health: nutrition, sanitation, housing, occupational safety, etc.
– What was one of the biggest changes to health/disease over the 20th
century? Cleaner air and water! - Politics:
– $ How much “health” are we willing to fund?
– What are we willing to give up? - Individual liberties, corporate profits, etc.
– Is our emphasis on curing disease rather than preventing it out of
control?
slide 7
What was one of the biggest changes to health/disease over the 20th
century? Cleaner air and water!
- British Cholera Epidemic
1848-1849:
– 616 deaths prompted
Snow (and others) to
investigate causes
– Based on his clinical
experience and review of
epidemiologic
characteristics of cholera,
Snow formulated a theory
of causation and
transmission of the disease
slide 13
John Snow Cholera Epidemic
Snow’s hypothesis
* Observations:
– A gastrointestinal disease, therefore causal agent was likely
ingested
– Diarrhea as most prominent symptom, therefore causal
agent likely left the body by this route
– If cholera excretions contaminated rivers from which
drinking water was taken, then the disease could be widely
disseminated
* Causal Hypothesis:
– Sewage-contaminated drinking water was a causal agent
for the cholera epidemic
slide 14
Layers of Prevention and Intervention
- Primary prevention
– Prevent illness/injury from occurring
– Discourage risk behaviors (e.g., smoking) - Secondary prevention
– Minimize severity or damage after event has occurred
– Screening for early stages - Tertiary prevention
– Further minimize overall disability
– Not always a huge distinction from “secondary”
– Medical treatment and rehabilitation
slide 9
Why is Public Health Controversial?
- Moral and religious opposition
– Sex education
– Provision of contraception
– Clean needle programs
– Safe and legal abortions - Political interference with science and research funding
– E.g., stem cell research, HIV research, climate change - Companies and private businesses are not always motivated to help their customers. They seek to earn profits.
slide 10
Powers and Responsibilities of Government
- U.S Constitution states that the fundamental purpose of the government is “to promote the general welfare”
-Reserve clause: health care is not mentioned in the Constitution so the responsibility for public health belongs to the states
-Interstate commerce provision justifies the activities of the Food and Drug Administration (FDA)
-Power to tax and spend is widely used by federal government to control public health policy (The federal government provides 65% of the funding for Medicaid)
slide 11
A word about global health governance
- World Health Organization (WHO)
– Serves as a clearinghouse for science that informs public health at global and regional levels.
– Can issue policy recommendations, but does not have a “jurisdiction” and therefore cannot enforce rules.
– Coordinates efforts at a global level – especially useful in pandemic response.
– Useful to think of WHO’s role as one of health diplomacy.
slide 12
“Descriptive” epidemiology
- Who, Where, When (and how many)
- Understand the state of population health and how it is changing
– E.g., Are we making progress in CVD, cancer?
– E.g., Are some diseases on the rise (or new)?
– Prompts questions of: WHY? - Interventions (e.g., screening, etc.), treatments, changes to
environment or behavior. - Understand disparities (e.g., by race-ethnicity, age, gender/sex, SES)
slide 15
Endemic vs Epidemic
- Endemic = the usual and expected rate of a
disease in a population - Epidemic = an increase in the frequency of a
disease above the usual and expected rate
slide 16
Analytic epi (How)
- We already know person, place, time because of the descriptive epi so we need to look at relationships to learn HOW epidemics occur:
– Explain why and how a health problem occurs
– Describe association between exposure and outcome
– Test a hypothesis about the cause of disease by studying how exposures relate to the outcome - These studies look at:
– Hosts
– Environments
– Agents
slide 17-18
Epidemiology
The study of the distribution, causes, and effects of health and disease in defined populations
* Distribution
* Causes (and effects)
– Really difficult to prove “causation”
– We are attempting to find/show associations
* E.g., HRT is associated with an increased risk of heart disease
* Correlation does not imply causation
– Also investigating risk factors (might not refer to as a “cause” per se
– Sometimes we say “disease.” Sometimes we say “health outcome.” These terms are often used interchangeably.
slide 19
Investigating Associations:
4 Types of Study Designs in Epi
- Cross-sectional
- Prospective cohort (longitudinal) – observational*
- Case-control – observational*
- Experimental/Interventional**
*Observational studies pose the least risk of harm.
**Experimental studies can potentially cause harm.
slide 20
Prospective Cohort Study
- Start with a defined population (cohort)…
- Some are exposed and some unexposed …
- Follow up and compare on development of disease
- Text examples
– Framingham Heart Study - CVD risk factors (BP, cholesterol, smoking) and heart disease
- But we didn’t know they were risk factors!
- There was no concept of “high” blood pressure (“hypertension”); considered a normal process of aging
– Nurses’ Health Study
* Oral contraceptives and breast cancer
* Regular consumption of alcohol increases risk of breast
cancer by 10% to 40%
slide 21-22
Case-Control Study
- Again, examine relation of an exposure to a disease
- Identify people with the disease (cases) match to people w/o the disease (controls) and …
- Start with two groups: disease (cases) and no disease (controls), and compare their prior exposure status
- Text examples
– EMS and L-tryptophan
– Reye’s syndrome and aspirin use in children - A primary distinction from cohort study is starting with cases rather than a cohort (pre-defined pop)
- Selection of cases
– Sources: hospitals, physician practices, disease registries, etc. (Be mindful of generalizability!) - Case-control study saves time over cohort. WHY?
– What if you’re waiting around for incident cases? - Advantages of over cohort designs
– Inexpensive
– Shorter time
– Requires smaller sample (good when disease rare) - Limitations
– Recall bias
– Difficulties selecting controls
– Cannot estimate disease incidence or prevalence.
WHY?
slide 23-26
Case study diagram
slide 27-37
Experimental/Interventional:
Randomized controlled trials (RCTs)
- Gold standard in research
– Control group
– Randomization - Planned experiment where investigators assign study participants to either an intervention or control group
- Trials are designed to test efficacy of intervention or clinical treatment
- They are often blinded to protect against breaches in ethics
– Blind – the participants don’t know treatment status, researchers know treatment status
– Double blind – neither participants nor researchers know treatment status
slide 38
Measuring Disease
Prevalence vs. Incidence
- Prevalence: # people who currently have a condition
– Often expressed as a proportion
– Implies a population at risk (the denominator)
– Sometimes called frequency
– E.g., 5%, or 50/1000 persons - Incidence: # of new cases/diagnoses
– Usually includes a time dimension – WHY?
– Also incorporates dimensions used/implied in prevalence
(i.e., 3 dimensions)
– E.g., 50/year, 50/1000 persons/year
slide 39
Prevalence
- Number of existing cases of disease in a
population - Can be expressed as a percentage or number of cases per unit size of population
- Indication of extent of health problem; helps us determine need and allocation of resources
Prevalence = Number of all cases (new + old)/Total population
slide 40
Incidence
- Rate of development of disease in a population over a certain time period
- Can help identify emerging diseases, reemerging diseases, or outbreaks
Incidence = Number of new cases/Total population at risk
slide 41
Prevalence vs. Incidence
Can be very different depending on the outcome
- Chronic and incurable (e.g., HIV/AIDS, arthritis, diabetes)
– Prevalence > incidence - Common and short-lived (e.g., STDs)
– Incidence > prevalence - Rapidly fatal (e.g., pancreatic cancer, acute
leukemia, Ebola, Dengue Hemorrhagic Fever)
– Incidence > prevalence
slide 47
Example of Incidence:
Disease Mortality
- Death rate/mortality rate = incidence of death
– E.g., 400 deaths/100,000/year - Note difference with prevalence: why do we not measure a “prevalence” for death?
slide 48
Types of Results
- True results:
– True positive: a test indicates disease when there is disease present
– True negative: a test indicates NO disease when there is NO disease present - False results:
– False positive: a test indicates disease when there is NO disease present
– False negative: test indicates NO disease when there is disease present
slide 49
SENSITIVITY
- The ability of a test to correctly identify those
who have the disease - Sensitive tests are good at finding positive results
– A sensitive test may be too good at finding positive results that it give false positive results
– A test with high sensitivity will have few false
negatives
slide 50
SPECIFICITY
- The ability of a test to correctly identify those
who do not have the disease - Specific tests are good at finding negative results
– A specific test may be too good at finding negative
results that it give false negative results
– A test that has high specificity will have few false
positives
RR vs OR
- Relative Risk (Risk Ratio) (RR)
– Used when comparing outcomes of those who were exposed to something to those who were not exposed
– Calculated in cohort studies
– Cannot be calculated in case-control studies because the entire population at risk is not included in the study - Odds Ratio (OR)
– Odds of exposure among cases divided by odds of exposure among controls
– Used in case-control studies
– Provides a rough estimate of the risk ratio
slide 52
Relative Risk (RR)
- Relative Risk (RR) = the ratio of the incidence for persons exposed to the factor to the incidence for persons in the unexposed group.
- Used in prospective cohort studies
slide 53
Strength of an Association
Table 5-1: Relative Risk of Lung Cancer by
Smoking Status
slide 54
Odds Ratio
- Odds Ration (OR) = a measure of the strength of an association between an exposure and a disease.
– OR is a ratio of two ratios.
– The numerator of the odds ratio is the ratio of exposed subjects to nonexposed subjects in the case group; the denominator is the ratio of exposed subjects to nonexposed subjects in the control group. - Odds Ratio used in case-control studies
slide 55
OR: Reye Syndrome case-control study
slide 56
Why can’t we use RR in case-control study?
- It is not possible to calculate the relative risk in a case-control study because this calculation requires knowing the rate of new cases in the exposed versus the unexposed groups – but the starting point of a case-control study is a group that already has the disease, which does not directly reveal the rate of new cases in a broader
population.
slide 57
Sources of Error
- Random variation = association merely due to chance
- Confounding variables
- Bias
slide 58
Confounding
- Associations may not reflect causation because of confounding
- We think (or hypothesize) that X causes Y
- We conduct an epidemiological study and observe that X and Y are, indeed, correlated (associated) – YAY!
- BUT what could lead to this observation?
– It might truly be the case that X causes Y (XàY)
– Or is it due to the relationships of X and Y to other variables (Z)
slide 59-60
Bias
- Bias = systematic error that can be introduced into a study in a number of ways.
- Bias may be introduced:
– in the selection of cases or controls (“selection bias”)
– in the reporting of exposures or outcomes (e.g., recall
bias; and purposeful suppression of data)
– in the disproportionate loss to follow-up of exposed or
unexposed groups (e.g., attrition)
slide 61
Ethics in Epi
- Abuses by Dr. Mengele, who conducted medical experiments on concentration camp prisoners during WWII
- Tuskegee syphilis experiment
- Tonsillectomies
- Institutional Review Boards (IRB)
– Big improvement over no ethics review
– But who do they really protect? The subjects or the institutions? - E.g., male genital cutting (circumcision) RCTs in African countries to
prevent HIV infection
– Conflicts of interest (pharmaceutical companies may profit from
favorable results of clinical trials)
slide 62
P-value
- The probability that the observed result could have occurred by chance alone
– I.e., that there really is no association or no difference
– What does “chance alone” mean?
– Typical threshold for “statistically significant” is 5%, or
p<0.05 - Example: sex balance is really 50-50, but you take a sample and compare %F vs. %M
– By chance alone, you might find a difference
– p = chance that difference = 0 (i.e., no difference)
slide 63
Epidemiologic Transitions
- Rise of infectious disease (urbanization)
– e.g., from rural life with death due to old age, to high-density
cities with death due to cholera and tuberculosis - “Conquest” of infectious disease followed by rise of
chronic disease
– e.g., from communicable diseases (plague) to “lifestyle”
diseases in rich countries (cancer) - Chronic disease rejoined by infectious disease
– e.g., while chronic disease remains (CVD), old infectious
diseases re-emerge (yellow fever, dengue fever, measles) and
novel pathogens emerge (SARS-CoV-2)
slide 64
The “Conquest” of Infectious Diseases
- Public health measures + antibiotics 1940s
- Means of transmission
- Chain of infection
– Pathogen, reservoir, method of transmission, susceptible host - Examples: rabies, smallpox (eradicated), measles
(new outbreaks), polio, malaria, dengue fever - Fear of vaccinations
- Herd immunity
slide 65
Chronic Disease Etiology
- Much more difficult to elucidate the “cause” of the following chronic diseases because their etiology is more complex than infectious
diseases.
– Cardiovascular disease
– Cancer
– Diabetes
slide 66
Quantifying the Burden of Disease
Different measures offer varying perspectives:
* Morbidity (incidence, prevalence)
* Deaths (mortality rate)
* Years of life lost (YLL)
* Years lived with disability (YLD)
* Disability-adjusted life years (DALYs)
slide 67
What is Culture
- Culture is a concept that helps us learn how groups of people make meaning of the world.
– Culture tells us what things mean, but also makes it possible for us to assign meaning to things. - A system that shapes our lived reality by organizing patterns of thoughts, beliefs, behaviors, ideas, and
assumptions about the world.
– Useful to think of culture as the “operating system” that
runs in the background of our lives.
– Shapes our ideas and guides our behaviors without us
being explicitly aware that these are conditioned
phenomena.
slide 68
Culture
- Culture shapes and is shaped by:
– Communication
– Orientation to space and time
– Social organization
– Family structure
– Gender roles
– Sexual practices
– Religion and interaction/membership in faith-based
community
slide 69
Disease v. Illness v. Sickness
- Disease = disordered physiology
– pathological changes in the body which have an organic basis, can be observed biologically, and are expressed in various physical signs and symptoms - Illness = an individual’s lived experience
– subjective interpretation and response to signs and
symptoms - Sickness = disordered social relations
– Interruption in relationships between an individual and
other people (taking a “sick day” from work; moral aspersions cast when others refer to behavior that is perceived as aberrant/deviant - “they’re sick in the head”)
slide 70
Medicalization
- “The process by which certain behaviors or
conditions are defined as medical problems…, and medical intervention becomes the focus of remedy and social control” (Chang and Christakis 2002) - Medicalization occurs when human problems or experiences become defined as medical problems, usually in terms of illnesses, diseases, or syndromes.
- Chang and Christakis examine changing ideas about obesity as they evolved from 1927 to 2000 in a widely-consulted medical school textbook.
slide 71
Medicalization:
Is It More Humanitarian?
- Unlike a moral or legal model, a medical model can reduce stigma and potentially lead to more humanitarian approach.
– E.g., obesity
– E.g., injection drug use - But is medicalization always better?
– Growth of ADHD diagnoses and prescribing of stimulant drugs for millions of children and adults?
slide 72
Socioeconomic Status (SES)
- SES (or sometimes socioeconomic position) refers to standing in the stratification system and is usually measured by education, occupation, employment, income, and wealth.
- SES can reflect diverse underlying theoretical
concerns such as material well-being, human capital, prestige, and productive relations.
– Although these components are not interchangeable, SES
is useful as a summary term what a particular measure does not have key importance.
slide 73
RACE
- Based on biological differences (phenotypes)
– “Race is the child of racism not the father” Ta-Nehisi
Coates - But race is a social construct
- The “One Drop” rule in the U.S.
- Compare to how race has been viewed in Brazil
Ethnicity
- Ethnic categories:
– A cultural marker or a place of origin with a shared cultural experience
– Sense of community
– Useful to think of as a sub-category of race, yet ethnicity can transcend more than one racial category - E.g. “Afro-Brazilian” and “African American”
– OR - E.g. “Black Hispanic” and “White Hispanic”
slide 75
RACISM & SEGREGATION
- Encompasses institutional and individual
discrimination, racial prejudice and stereotypes, and internalized racism - Separated neighborhoods based on the grouping of racial or ethnic groups
- Why does segregation have an impact on health?
slide 76
WHAT IS SEX?
WHAT IS GENDER?
slide 77
GENDER
- Refers to roles, behaviors, activities, and attributes that a society considers appropriate for men and women
– Does not always imply a binary
– “Third” categories (e.g., transgender, non-binary, two-spirit) - Is socially constructed: What is considered
appropriate varies by society, culture, and place in history (it changes over time) - “Cisgender,” a term that recently entered the popular lexicon, refers to identifying or experiencing a gender that is the same as the sex assigned at one’s birth.
slide 78
Why the paradox of men’s higher mortality
and lower morbidity?
- Gender gap in longevity in the United States has been closing since 1980. Why?
- Men’s rapid decline in smoking and decreasing mortality from
cardiovascular disease (CVD) and cancer - Women’s risk for CVD increases after menopause
- Men have more life-threatening chronic diseases at younger ages (CHD, cancer, cerebrovascular disease, emphysema, liver
cirrhosis, kidney disease, and atherosclerosis) - Women have more chronic debilitating disorders (autoimmune diseases and rheumatologic disorders) and less
life-threatening diseases (anemia, thyroid conditions, gallbladder conditions, migraines, arthritis, and eczema)
slide 79
