Measuring Association

Question 1

define cause

Answer 1

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

Question 2

what does disease result from?

Answer 2

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

Question 3

what are the 3 types of causes?

Answer 3

1. necessary cause
2. contributing cause
3. sufficient cause

Question 4

descrine necessary cause

Answer 4

found in all case

Question 5

describe contributing cause

Answer 5

needed in some case

Question 6

describe sufficient cause

Answer 6

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

Question 7

what do you need before you can start determining causes?

Answer 7

a case definition!

Question 8

what is causal complement/causal pie?

Answer 8

the set of factors that completes a sufficient causal mechanism

Question 9

give an example of causal complement in tuberculosis

Answer 9

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

Question 10

define and give 7 examples of host factors

Answer 10

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

Question 11

what is needed to determine relative risk?

Answer 11

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

Question 12

what is exposure?

Answer 12

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

Question 13

what is risk?

Answer 13

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

Question 14

how is risk calculated?

Answer 14

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

Question 15

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

Answer 15

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!

Question 16

what is relative risk?

Answer 16

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

Question 17

what do you need to calculate relative risk?

Answer 17

case definition!!!

Question 18

what does relative risk (risk ratio) compare?

Answer 18

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

Question 19

how is risk ratio calculated?

Answer 19

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

Question 20

what is attack rate similar to?

Answer 20

very similaer to risk rate in both concept and calculation

Question 21

what is attack rate commonly?

Answer 21

a measure of infectivity

Question 22

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

Answer 22

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

Question 23

what would lower the attack rate?

Answer 23

vaccines

Question 24

what is attack rate really a measure of?

Answer 24

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

Question 25

give the formula to calculate attack rate

Answer 25

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

Question 26

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

Answer 26

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

Question 27

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

Answer 27

no

Question 28

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?

Answer 28

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

Question 29

how are controls selected when calculating odds?

Answer 29

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

Question 30

what does odds measure?

Answer 30

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

Question 31

what must odds be calculated for?

Answer 31

both the cases and the controls

Question 32

how are odds for cases calculated?

Answer 32

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

Question 33

how are odds for controls calculated?

Answer 33

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

Question 34

what is odds ratio?

Answer 34

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

Question 35

how is odds ratio calculated?

Answer 35

odds for cases over odds for controls

Question 36

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

Answer 36

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

Question 37

what do the signs of odds ratio mean?

Answer 37

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

Question 38

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

Answer 38

yes, but includes a margin of error

Question 39

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

Answer 39

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

Question 40

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

Answer 40

the error factor for the odds ratio

Question 41

what is the error factor for the odds ratio?

Answer 41

the plus or minus; the confidence interval

Question 42

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

Answer 42

when extrapolating the odds ration to another population

Question 43

how do you decrease the error factor of odds ratio?

Answer 43

increase the sample size

Question 44

compare and contrast relative risk versus odds ratio

Answer 44

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

Question 45

when is odds ratio a good estimate for risk rate?

Answer 45

in cases of low frequency disease

Question 46

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

Answer 46

in a rare disease