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Epidemiology and Public Health > Measuring Association > Flashcards

Measuring Association Flashcards

1
Q

define cause

A

any event, act, or condition preceding disease or illmess without which disease would not have occurred or would have occurred at a later time

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2
Q

what does disease result from?

A

the cumulative effects of multiple causes acting together (causal interaction)

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3
Q

what are the 3 types of causes?

A
  1. necessary cause
  2. contributing cause
  3. sufficient cause
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4
Q

descrine necessary cause

A

found in all case

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5
Q

describe contributing cause

A

needed in some case

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6
Q

describe sufficient cause

A

the constellation of necessary and contributing causes that make disease inevitable in an individual

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7
Q

what do you need before you can start determining causes?

A

a case definition!

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8
Q

what is causal complement/causal pie?

A

the set of factors that completes a sufficient causal mechanism

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9
Q

give an example of causal complement in tuberculosis

A

the necessary agent is mycobacterium tuberculosis, the causal complement is one’s susceptibility to the bacteria

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10
Q

define and give 7 examples of host factors

A

aspects of the host that contribute to a disease state
1. genetics
2. physiology
3. anatomy
4. behavior
5. occupation
6. constitutional
7. cultural

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11
Q

what is needed to determine relative risk?

A

one must examin each potential risk factor and calculate the relative risk

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12
Q

what is exposure?

A

exposure to the risk factor, not necessarily exposure to the causative agent

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13
Q

what is risk?

A

the proportion of individuals exposed to a risk factor that become ill

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14
Q

how is risk calculated?

A

the number of cases that become ill divided by the total number of people exposed to the risk factor

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15
Q

what does risk NOT tell you? how do you fill this knowledge gap?

A

does not tell anything about thosenot exposed to the risk factor who could also be ill; go talk to the people who are sick! shoe leather!

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16
Q

what is relative risk?

A

the relative chance of becoming a case upon exposure to the risk factor compared to those not exposed

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17
Q

what do you need to calculate relative risk?

A

case definition!!!

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18
Q

what does relative risk (risk ratio) compare?

A

compares the risk of becoming a case between the exposed and unexposed groups

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19
Q

how is risk ratio calculated?

A

risk in those exposed divided by risk in those not exposed
a/(a+b) over c/(c+d)

20
Q

what is attack rate similar to?

A

very similaer to risk rate in both concept and calculation

21
Q

what is attack rate commonly?

A

a measure of infectivity

22
Q

what does attack rate do for a person-to-person spread infection?

A

limits the number of exposed individuals to those that are both exposed and susceptible

23
Q

what would lower the attack rate?

A

vaccines

24
Q

what is attack rate really a measure of?

A

communicability, or the ability of a disease to spread person-to-person

25
Q

give the formula to calculate attack rate

A

(number of new cases among the population during the time period divided by population at risk) x100

26
Q

what is calculating risk, relative risk, and attack rate all dependent upon?

A

knowing everything about the population that you have narrowly defined; true for both cases and controls where you know how many are involved and how many are susceptible

27
Q

can the results of risk, relative risk, and attack rate be extrapolated outside of the defined population?

A

no

28
Q

what must one do when the population is poorly defined or one cannot be confident that all of those exposed to the risk factor are accounted for?

A

play the odds to make statistical comparisons between two samples of peple, cases, and controls

29
Q

how are controls selected when calculating odds?

A

controls should be selected from those most likely at risk for exposure, yet did not develop the disease

30
Q

what does odds measure?

A

the odds of having been exposed to the risk factor versus the odds of not being exposed to the risk factor

31
Q

what must odds be calculated for?

A

both the cases and the controls

32
Q

how are odds for cases calculated?

A

number of cases exposed to RF over number of cases not exposed to RF

33
Q

how are odds for controls calculated?

A

number of controls exposed to risk factor over number of controls not exposed to risk factor

34
Q

what is odds ratio?

A

analogous to relative risk, but this calculates the odds for exposure among cases divided by those for controls

35
Q

how is odds ratio calculated?

A

odds for cases over odds for controls

36
Q

what is the only real difference between odds ratio and risk ratio?

A

the ambiguity of data on the population as a whole (more ambiguous with odds ratio)

37
Q

what do the signs of odds ratio mean?

A

OR =1: no assocation between risk factor and disease
OR<1: negative association (risk factor protective against disease)
OR>1: positive association: risk factor indicative of disease

38
Q

can odds ratio be extrapolated to other populations? what does it include?

A

yes, but includes a margin of error

39
Q

why is there statistical uncertainty for each of the four groups in the contigency table made from odds ratio?

A

because we do not have that actual data for the entire population involved

40
Q

what must you also calculate with odds ration due to the statistical uncertainty?

A

the error factor for the odds ratio

41
Q

what is the error factor for the odds ratio?

A

the plus or minus; the confidence interval

42
Q

when do you need to factor in the error factor of the odds ratio?

A

when extrapolating the odds ration to another population

43
Q

how do you decrease the error factor of odds ratio?

A

increase the sample size

44
Q

compare and contrast relative risk versus odds ratio

A

relative risk needs incidence of the disease, is prospective, and demonstrates temporality while odds ratio does not require incidence for its calculation and is retrospective

45
Q

when is odds ratio a good estimate for risk rate?

A

in cases of low frequency disease

46
Q

when can odds ratio overestimate the risk rate of a disease?

A

in a rare disease

Epidemiology and Public Health (13 decks)

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