BIOL 437 Week Ten p.1 (Causality)

Question 1

when a causal association is established

Answer 1

-a protection and control attitude can occur vs. a reaction to the health crisis

Question 2

cause

Answer 2

-a specific event, condition, or characteristic that precedes the health outcome and is necessary for its occurence

Question 3

“necessary” cause

Answer 3

• if an environmental exposure is required for the outcome to occur
• without it, effect will not occur

Question 4

“sufficient” cause

Answer 4

• if the health related event always occurs becuase of the exposure
• with it the effect will result regardless of the presence or absence of other factors

Question 5

related terms to cause

Answer 5

• risk factor
• at-risk behaviour
• predisposing factor

Question 6

historical perspecitve of causation

Answer 6

• central topic in philosophy of science

- concepts of disease causation change over time

Question 7

1950s

Answer 7

-a common belief that we had “conquered” infectious diseases and knew there all there was to know

Question 8

19th century decline in death rates due to infectious disease and malnutrition

Answer 8

• few decades before medical discoveries of scientific revolution became policies
• not realized until later on
• changes in sanitiation and living standards had a lot to do with the decline

Question 9

18th century (1776)

Answer 9

-small pox inoculation stopped epidemics

Question 10

Edward Jenner (1796)

Answer 10

-‘father of vaccination’

>demonstrated immunity to smallpox in people who had previously had cowpox

Question 11

18th century yellow fever

Answer 11

• contagious
• imported
• quarantine of sick people and ships suspected of having it on board

Question 12

Miasma theory (end of 18th century)

Answer 12

-all disease due to bad air

Question 13

miasma theory dominated thinkin (early 19th century)

Answer 13

-prevention was aimed at eliminating miasma in slums and poor sanitation
>sanitation measures were very effective in decreasing death rates

Question 14

Louis Pasteur

Answer 14

-existence of microorganisms (germ theory)
-inference to direct observation
-prevention: containing spread of microbes
-*germ theory replaced miasma theory= paradigm shift
>explained and predicted immunization and chemotherapy which miasma theory could not

Question 15

germ theory lead to

Answer 15

• illnessa cuased by different agents
• ‘one disease one-cause model’
• ‘theory of specific etiology of disease’
• specific causation

Question 16

concept of specificity

Answer 16

• still applied and led to many medical achievements (ex. worldwide eradication of smallpox)
• even when not due to micro-organisms is still valid (ex. James Lind: scurvy and vitamin C)

Question 17

complexity of relationship between cause and effect

Answer 17

-not addresed to real world until late 1950s

Question 18

events that put one-cause disease model into question

Answer 18

• opportunitistic infections
• pathogens can be present for a long period of time before causing disease
• shift from infectious to chronic disease (ex. cancer)

Question 19

epidemiology triangle

Answer 19

-characterizes infectious disease causation by interaction and interdependance between agent, host, environment and time

Question 20

agent

Answer 20

• a causative factor

ex. pathogen or chemical

Question 21

host

Answer 21

• an organism

- usually a human

Question 22

host factors

Answer 22

• intrinsic factors that influence exposure, susceptibility or response to causative agent
  ex. race, age

Question 23

environmental factors

Answer 23

• extrinsic factors that affect the agent and opportunity for exposure
  ex. climate, geology, biological factors, psychosocial factors

Question 24

epidemiological research now

Answer 24

• often examines single risk factors
• greatest impact during early investigation steps before causal info is known
• suspected factors increase the predictive power of the investigation
• one factor at a time method is key to risk factor epidemiology

Question 25

unplanned or natural experiments

Answer 25

• take advantage of groups of people exposed for non-study purposes
  ex. occupational cohorts in specific industries

Question 26

approach steps to etiology

Answer 26

1. Clinical observations
2. Available data
3. Case-control studies
4. Cohort studies
5. Randomized trials

Question 27

determine whether there is an assoication or correlation

Answer 27

• studies of group characteristics (ecological studies)

- studies of individuals characteristics (cohort, case-control and other types of studies)

Question 28

If association is determined

Answer 28

-determine whether the observed assocition is likely to be a causal one

Question 29

causal relation attributes

Answer 29

1. Association
2. Time order
3. Direction

Question 30

association

Answer 30

-cause is assosicated with an effect

Question 31

time order

Answer 31

-cause is present before or at same time as its effect

Question 32

direction

Answer 32

-cause acts on its effect

Question 33

direct causation

Answer 33

-a factor directly causes a disease without an intermediate step

Question 34

indirect causation

Answer 34

-a factor causes a disease, but only throught an intermediate step or stpes
>intermediate steps are generally always present in causal process involving biology

Question 35

Causal pies (Rothman)

Answer 35

-accounts for multifactorial nature of causation for many non-infectious diseases

Question 36

pieces of the pie

Answer 36

-individual factors
*component causes
>intrinsic host factors
>agent factors
>environmental factors
>time

Question 37

complete pie

Answer 37

• caussal path/mechanism that is “sufficent cause”

- a disease can have more than one suffient cause

Question 38

a component in every pie or pathway

Answer 38

• is a ‘necessary cause’

* without it the disease cannot occur

Question 39

disease prevention can be

Answer 39

-accomplished by blocking any single component of a sufficent cause (at least through that pathway)

Question 40

4 types of causal relationships

Answer 40

1. Necessary and sufficent
2. Necessary but not sufficient
3. Sufficeint but not necessary
4. Neither sufficent or necessary

Question 41

necessary and sufficient

Answer 41

• without the factor, the disease never develops (necessary)
• disease always develops in the presence of the factor (sufficent)
• this situation rarely occurs (one-to-one relationship)
  ex. in most infectious diseases, a number of people are exposed, some of whom will manifest the disease and others who will not

Question 42

necessary but not sufficent

Answer 42

• multiple factors are required, often in a specific temporal sequence
  ex. carcinogenesis is a multistage process involving initation and promotion

Question 43

suffiecent but not neccessary

Answer 43

-factor alone can produce the disease ,but other factors that are acting alone can too
ex. radiation exposure or benezene exposure can each produce leukaemia without the presence of the other
>but cancer does not develop in everyone who has experiened either one

Question 44

neither sufficent or necessary

Answer 44

• more complex

- probably most accurately represents the causal relationships that operate in most chronic diseases