Social Epidemiology Midterm 1

epidemiology (literally)
the study of what is upon the people

traditional medical perspective
biological and physical risk factors in individuals; risk factors for specific disease in individuals

traditional epidemiological perspective
determinants of health and disease in populations; spread of disease in populations

an acute diarrheal illness caused by infection of the small intestine with the bacterium vibrio cholerae

number of infected persons
one in 20 has profuse watery diarrhea, vomiting, and leg cramps

rapid loss of body fluids leads to
dehydration and electrolyte imbalance

without treatment, death can occur within

altitude hypothesis
Farr (1852)

John Snow
“Father of Epidemiology”

cause of cholera
Snow suspected that cholera was carried by water; challenge was to test the hypothesis; Broad Street Documentary

On the Mode of Communication of Choler (1855)
reported analysis of earlier outbreaks over London districts

Compared water suppliers to different homes in the same districts
Southwark and Vauxhall vs. Lambeth

In 1853, after Lambeth moved its water intake up the Thames,
its customers had lower cholera levels

attack rate
the cumulative incidence of an infection in a group observed over a period during an epidemic

attack rate determined by
identifying cases and population at risk for disease

study of distribution and determinants of disease across populations

social epidemiology
branch of epidemiology that studies the social distribution and social determinants of health

social determinants of health
circumstances in which people are born, grow, live, work, and age, in cluding the health system

social determinants circumstances are shaped by
political, social, and economic forces

Why study social determinants of health? “The social determinants of health are mostly responsible for…
health inequalities or the unfair and avoidable differences in health status seen within and between countries.”

social environmental factors
-Childhood SES and adult health
-income inequality
-discrimination and stigma
-social capital and support
-work environments

social determinants
-social experiences
-circumstances in which people live
-healthcare systems

John Snow
father of modern epidemiology; did systematic investigation of cholera epidemic; first PH intervention; lays groundwork of epidemiology; took handle off broad street; emphasis primarily on population-levels

cholera eliminated worldwide?
no; prevalent in non-sanitary water areas

disease passed by not washing hands; can cause dehydration; easy to cure

a state of complete physical, mental, and social well-being and not merely the absence of disease or infirmity

what is health?
“the extent to which an individual or a group is able to realize aspirations and satisfy needs, and to change or cope with the environment”

measuring health in clinical practice
specificity and detail; individual’s biological status

measuring health in social surveys
plain, comparable, concise, general, common

measring health
1. subjective health
2. physical impairment
3. vitality and mental well-being
4. awareness of disease and risk to life
5. the absence of disease

1. Self-Report
no medical diagnosis, single item that measures it or “perceived” health; correlates with physician diagnoses; predicts mortality

2. physical impairment
acute chronic conditions, fatal and nonfatal disease, functional ability or impairment, general well-being

physical impairment, how much difficulty in
climbing stairs, kneeling or stooping, lifting/ carrying objects, hearing, seeing, shopping, household work

felt physically fit, had lots of energy, enjoyed life, was happy, was hopeful about the future

3. mental well-being (depression or anxiety)
CESD (centers for epidemiologic studies dpression scale);

diagnostic and statistical manual of the american psychiatric association, 4th revision–current standard for “caseness”

clinical diagnosis into categories based on
intensity and number of symptoms

4. Measuring Health
awareness of disease and risk to lif

5. Presence of disease as a measure of poor health
morbidity and mortality weekly report (MMWR)

Measuring Health
1. Subjective
2. Physical Impairment
3. Mental well-being
4. Awareness of Disease/Risk to Life
5. Absence of Disease (or conversely presence of disease)

general pattern of subjective health by poverty status
lower income individuals report bad health

general pattern of subjective health by ethnicity
same for all races (black are more likely 2nd is hispanic)

Why is the WHO definition of Health sometimes criticized?
it stresses presence of well-being and social function; can’t measure or quantify it; amended it to any good measure of health should have

mental disorders are diagnosed using

rate =
# of events in specific time/ pop. at risk in specific time

if event is a disease
morbidity rate

if event is a death
mortality rate

a specific type of ratio; numerator is included in denominator

expresses probability or risk of disease in a defined population over a specified period of time

incidence rate
measures risk that healthy people will develop a disease during a specified time period

measures probability of people having a disease at given point in time, aka “point prevalence”

incidence rate =
# new cases of disease in specific time / pop. at risk of disease in specific time

prevalence rate =
# existing cases of disease at point in time / total pop. at point in time

measuring incidence requires
follow-up of population orprosepctive study

measuring prevalence
no prospective follow-up, but rather can be estimated from cross-sectional study

incidence requires knowledge of
population; disease/non-disease confirmed by physician report screening, health records, self-report

incidence requires time of
onset of disease; straight forward for colds, flu, not for others (e.g., cancer)

incidence requires numerator
# of persons vs. # of conditions if counting # of conditions, not “true” incidence rate

incidence requires denominator
over time; only at risk for developing the disease

use midpoint
when population changes over time

person-time denominator
used when study subjects are observed for different periods of time; weighs each person’s contribution interms of time observed in the denominator of the incidence rate

person years calculation
number of events / sum of years of follow-up

incidence rates
direct indicators for burden of diseases in populations

assumptions necessary to use person-years denominator
1. risk of disease (or death) constant throughout entire period of study
2. rate of disease in group lost to follow-up is same as group followed

prevalence depends on 2 factors
number of people who are sick with disease and duration of illness

prevalence =
prevalence x duration

prevalence is useful for
planning of facilities and manpower for treatment of chronic disease; tracking changes in disease patterns over time

crude birth rate =
# live births during year / average (mid year) population

age-specific death rate
# of deaths among persons of given age group in a year / average (mid year) pop in specified age group

cause-specific death rate
number of deaths from stated cause a year / average mid year population

the most commonly used statistic to quantify or measure disease in populations

what is incidence?
number of disease free people who develop disease over time

what is prevalence?
number of existing disease over total population

prospective cohort study
begins with group free from disease but can be classified according to “exposure”. followed to see development of disease. ex. exposure is smoking, disease is lung cancer; risk factor measured 1st

retrospective study
people diagnosed with disease (case) are compared with persons without disease (controls) in terms of past “exposure” experience; outcome is measured first then backwards; ex: lung cancer and smoking

cohort design

case control design

sample survey

longitudal surveys

trend vs. panel surveys

over time with different samples; ex: current pop. survey;

track changes in same people

internal validity
degree to which variation in outcome variable can be attributed to presumed causal variable and not some other source

research designs with high internal validity allow
high confidence in the causal inference

causal inference
1. strength of association
2. presence of dose relationship
3. consistency of association
4. temporal correctness
5. biological plausibility
6. confounding

rule out plausible rival explanations for observed association

causal direction between
social indicator and health

nature of association
the lower an individual’s socioeconomic position, the worse their health

most widely accepted causal direction of social indicator and health
social causes health

what are the mediators between low SES and poor health?
social disadvantage and multiple risk exposure

moderated relationship
relationship between SES ad health different for whites than blacks

mediator between SES and health

cap the ends of chromosomes and shorten with age; the shorter its length, the more cardiovascular disease and mortality

race “moderates” the ______ between SES and Cellular ageing
telomere length

among white males, those with low SES had
shorter telomeres and change in length over 5 yrs

among black males,
SES was not related to telomere length

4 types of relationships between social indicators and health
1. association
2. direct causal
3. mediated
4. moderated

indirect causatio

interaction is present

social indicators of a person are used to predict health of the person

aggregate or ecological-level
social indicators of an area (eg, census tract) are used to predict health of the eighborhood

Robinson Study 1950
at ecological level, high liear correlation, but idividual level no correlation

Robinson’s conclusion
ecological correlations does not equal individual correlations (ecological fallacy)

areas include different types of individuals, and individuals between individuals account for the observed differences between areas

there are features of social or physical environment that influence the health of those exposed (i.e., those who live in the area)

Area Features Affecting Health
1. physical features of the environment shared by residents
2. availability of healthy environment at home
3. services provided, publicly or privately, to support people in their daily lives
4. sociocultural features of a neighborhood
5. reputation of the area

Child care subsidies and child development
[PDF] from
UC-eLinksCM Herbst… – Economics of Education Review, 2010 – Elsevier
Research is mixed,
Some studies find significant effects
Others do not

Cross-level relationship
social indicators of the neighborhood are combined with individual-level characteristics to predict health of the individual

mediation for multi-level relationships
social indicators cause poor health

Moderated for multi-level relationships
low SES and health but is it the same for everybody?

Example of Cross-Level Interaction:
Poor individuals living in poor neighborhoods experience worse health than poor individuals who live in wealthy neighborhoods.

The relationship between poverty and health depends on
the type of neighborhood one lives in