chap 4

Question 1

an event, condition or characteristic that plays an essential role in producing an occurrence of the disease.

Answer 1

“Cause”

Question 2

disease determinants can be categorized as?

Answer 2

agent, host, environmental factors

Question 3

The way in which factors interact to cause disease

Answer 3

web of causation

Question 4

those characteristics of some individuals which, on the basis of epidemiological evidence, are associated with increased risk of disease.

Answer 4

risk factors

Question 5

koch postulate

Answer 5

Koch’s postulates were the first rules to prove that a specific microorganism causes a specific disease. They state that the microbe must be found in sick but not healthy individuals, isolated and grown in pure culture, cause the same disease when introduced into a healthy host, and finally be re-isolated from that host. While very useful, they have limits because not all microbes can be cultured and some diseases have multiple causes.

Question 6

evan’s postulate

Answer 6

Evan’s postulates were developed. They expand the idea by requiring statistical evidence, group comparisons, biological responses (like antibodies), and proof that eliminating or preventing the factor reduces disease.

Question 7

the degree of dependence or independence between two variables.

Answer 7

association

Question 8

types of association

Answer 8

non-statistical, statistical

Question 9

arises by chance;
The frequency of joint occurrence of the disease and hypothesized causal factor (HCF) is no greater than what would be expected by chance. o In this association, a factor cannot be inferred as causal.

Answer 9

non-statistical association

Question 10

– arises more or less frequently than by chance
When the variables arise more frequently than would be expected by chance, they are positively statistically associated.
When they arise less frequently than would be expected by chance, they are negatively statistically associated.

Answer 10

statistical association

Question 11

T OR F Positive associations may indicate a ‘causal relationship’ all the time

Answer 11

F not all the time

Question 12

__________ can be causally associated either directly or indirectly .

Answer 12

Explanatory and response variables

Question 13

There is identifiable relationship between exposure or presence of a factor and disease (co-existence) (FD).

Answer 13

association

Question 14

There is presence of mechanism that leads from factor to disease (cause-effect) (F D).

Answer 14

causation

Question 15

there must be some actual relationship between two variables

Answer 15

association

Question 16

factor (explanatory variable) must precede disease (response variable)

Answer 16

time order

Question 17

effect can’t be explained in terms of some third variable

Answer 17

Non-spuriousness

Question 18

give the criteria for probabilistic causality

Answer 18

association, time order, non-spuriousness

Question 19

Because one cannot rewind history and replay events after making small controlled changes, causation can only be inferred, never exactly known.

Answer 19

counterfactual

Question 20

Goal of analytic study uses:

Answer 20

identical twins
comparison groups

Question 21

The likelihood or probability of an individual in a defined population developing a disease or other adverse health problem

Answer 21

risk

Question 22

a variable associated with an increased risk of disease or infection.

Answer 22

risk factor

Question 23

the relationship of causes to their effects allows classification of causes into two types: ‘necessary’ and ‘sufficient’

Answer 23

sufficient-component cause model or causal pie

Question 24

A factor needed for the
development of disease. A
disease cannot develop in its
absence. * Its presence does not ensure
that disease will occur, but
the presence of disease
means it must have occurred.

Answer 24

necessary caus

Question 25

A factor that inevitably(always) produces or initiates disease. * However, other events may also cause B, and thus B’s presence does not ensure presence of A.

Answer 25

sufficient cause

Question 26

– increase the level of susceptibility in the host (e.g. age, immune status)

Answer 26

Predisposing factors

Question 27

– facilitate manifestation of a disease (e.g.housing, nutrition)

Answer 27

Enabling factors

Question 28

associated with the definitive onset of disease (e.g. many toxic and infectious agents)

Answer 28

precipitating factors

Question 29

tend to aggravate the presence of disease (e.g. repeated exposure to an infectious agent in the absence of an immune response)

Answer 29

reinforcing factors

Question 30

Direct and indirect causes represent a chain of actions, with the indirect causes activating the direct causes. When many such relationships occur, a number of factors can act at the same level (but not necessarily at the same intensity), and there may be several levels, producing a

Answer 30

web of causation

Question 31

f death refers to the disease, failure of injury whose symptoms cause the person to die. However, the actual mechanism of death, e.g. cardiac arrest or heart failure, are not regarded as immediate causes of death. The immediate cause of death is recorded in the death certificate and saved in the statistical data files, but it is not used in the compilation of annual statistics.

Answer 31

immediate cause

Question 32

the condition(s)that led to or precipitated the immediate cause of death, as recorded on a death certificate. For example, myocardial ischemia caused by coronary artery disease is an antecedent cause of heart failure (the immediate cause of death), where the underlying cause is coronary arterial atherosclerosis.

Answer 32

intermediate cause

Question 33

defined by the World Health Organization (WHO) as the disease or injury that initiated the train of events leading directly to death, or the circumstances of the accident or violence which produced the fatal injury

Answer 33

underlying cause of death

Question 34

enumerate the formulating causal hypothesis

Answer 34

method of difference, agreement, concomitant variation, analogy

Question 35

the frequency of a disease is different in two different circumstances, and a factor is present in one circumstance but is absent from the other, then the factor maybe suspected of being causal.

Answer 35

method of difference

Question 36

If a factor is common to a number of different circumstances in which a disease is present then the factor maybe the cause of disease.

Answer 36

method of agreement

Question 37

This method involves a search for a factor, the frequency or strength of which varies continuously with the frequency of the disease in different situations.

Answer 37

method of concomitant variation

Question 38

This method involves comparison of the pattern of disease under study with that of a disease that is already understood, because the cause of a disease that is understood may also be the cause of another poorly understood disease with a similar pattern.

Answer 38

method of analogy

Question 39

give the features of good hypothesis

Answer 39

population, cause, outcome, dose response, time response

Question 40

give the principles in establishing causal association

Answer 40

time sequence of events strength of the association biological gradient consistency compatibility with existing knowledge specificity of association

Question 41

cause must precede effect.

Answer 41

time sequence of events

Question 42

if a factor is causal then there will be a strong positive statistical association between the factor and the disease.

Answer 42

strength of the association

Question 43

if a dose-response relationship can be found between a factor and a disease, the plausibility of a factor being causal is increased. This is the basis of reasoning of concomitant variation.

Answer 43

Biological gradient

Question 44

if an association exists in a number of different circumstances, then a causal relationship is probable. There is consistent findings across different populations in differing circumstances with different study designs.

Answer 44

Consistency

Question 45

– the proposed causal mechanism is biologically plausible; there is a mechanism of action, evidence from previous studies. Also, the causal mechanism must not contradict about what is known about the natural history and biology of the disease.

Answer 45

. Compatibility with existing knowledge

Question 46

an exposure leads to a single effect, or affects people with a specific susceptibility. It is easier to support causation when associations are specific, but this may not always be the case (many exposures cause multiple diseases).

Answer 46

Specificity of Association

Question 47

– provides the strongest and most directepidemiologic evidence on which to make a judgmentaboutdexistence of a cause-effect relationship

Answer 47

experimental

Question 48

Determining whether d observed associationis likelytobecausal on d basis of observational epidemiologicdata

Answer 48

Causal inference

Question 49

Epidemiology draws an inference about theexperienceofanentire population based on study of only a sample Determined by sample size * Extent of chance: p-value, confidence interval

Answer 49

chance

Question 50

Occurs when the group actually studied does notreflectthesame distribution of factors (age, sex, etc) as occursinthegeneral population and the factors influencetheoutcome.

Answer 50

selection bias

Question 51

Situations that introduce bias:

Answer 51

use of volunteers, 2) losses to follow up, 3) wrong choice of comparison group

Question 52

Result of the errors in measurement of factor/exposureanddisease or both result in misclassificationof subjects

Answer 52

Information Bias

Question 53

Mixing of the effect of a 3rd variable that is associated with the factor and a risk factor of disease

Answer 53

Confounding (spuriousness)

Question 54

confounding is controlled by

Answer 54

Randomization 2. Matching 3. Stratified analysis 4. Multivariate analysis

Question 55

No single study is sufficient for causal inference Causal inference is not a simple process (consider weight of evidence, requires judgment and interpretation)

Answer 55

Causal inference realities

Question 56

what is the goal of epidemiology

Answer 56

to estimate d value of d parameter w/little error

Question 57

Difference between the population value of the parameter beinginvestigatedand the estimate of this value based on different samples 2. All epidemiologic studies are considered to have sampling errors because the study population is considered a sample from a broader population

Answer 57

Random error (sampling error)

Question 58

Distortion in the estimation of magnitude of association (deviationfromthetruth) 2. Internal validity 3. Lack of systematic error 4. External validity 5. The extent to which the results of a study can be generalized or extended to others

Answer 58

Systematic error (biases and confounding)