enst exam 2 review - lecture 8

what is epidemiology

study of the causes, patterns of distribution and control of diseases in populations

• determine diseases cause/origins ( biology)

• establish disease patterns

• determine relative risk to a population

• aid in designing control/prevention strategies

what are Koch postulates to determine germs as causative agents of various diseases

• microgorganism ( germ) must be found in all organisms suffering from the disease, but not in healthy organisms

• germ must be isolated from diseased host, grown in pure culture and identified

• when introduced back into a healthy unaffected host, the cultured germ must causes disease

• able to re- isolate the germ from now “diseased” experimental host and identify it as identical to the original causative agent

who is Mary mallon

women who was a cook and an asymptomatic carrier of typhoid - passed through food

• at least 47 people were infected due to her being unaware

• 3 people died

-disaproved koch’s first postualte as she was an infected org but still was a carrier

what year did Koch win the Nobel peice prize what diseases did he find the causative agents to ?

• 1905

• anthrax, tuberculosis, and cholera

define environmental epidemiology

study of the effect on human health of biological, chemical, and physical factors in external environment

• studies environmental agents to which large numbers of people are exposed to involuntarily

• identify relationships/associations between “agents” and “effects”

rarely “proves” cause and effect since it's difficult to control confounding variables and very few non-biological agents produce unique/distinct health effects

what is( Austin) hills criteria of causation

1) in order for a to cause B, A must always proceed B

2) strength of association ( strong association are more likely to be causial than weaker association)

3) dose-response relationship ( relationship to the dose of something to reponse It draws in a person)

4) relationships need to be consistent and able to reproduce the same results in different populations and circumstancce

5) specificity ( single relationship between a single cause and a single effect)

6) scientific plausibility

7) analogy/experimental evidence

8 ) coherence: compatibility with existing theory

what are the three types epidemiological studies

• descriptive ( data gathering/ hypothesis generating - not actually testing )

• analytical (clinical trials, drug test, animal test)

• observational ( environmental epidemiology)

what is a descriptive epidemiological study

~ describe pattern of diseases occurrence in terms of broad demographic variabes such as age, gender, season

~ variables can be endogenous or exogenous

what are observation epidemiological study

• test relationships observed in descriptive studies

• takes advantage of the naturally occurring agents and investigates resulting effects

what are the three types of observational epidemiological studies

• cohort

• case control

• cross sectional

cohort study

follows a group of exposed and non exposed people of an agent over time ( non diseased groups)

compare the rates of disease in each group after a pd of time

• good for common disease

~ prospectively ( looking into the future): can be accurate, but slow and expensive

~ retrospectively ( looking backwards): quicker and cheaper, but prone to bias and inaccuracy

what are case control study

tries to determine relationship between causative agent and a disease by looking back through time to establish risk factors and exposure history of diseases and non diseased groups

• only retrospective

• prone to inaccuracy due recall bias

• useful for rare diseases

what Is a cross sectional study

• study that observe exposure and effect at the same point time

• cheaper and fasted but less accurate

• diffcult to determine if a proceeded B

what is relative risk

raito to the incidence among those exposed to the incidence among those not exposed

how to calculate relative risk

rr= incidence among those exposed/ incidence among those not exposed