Lecture 11

Question 1

what can quantitating mortality do?

Answer 1

• shows difference in the risk of dying for a disease between groups
• measures disease severity
• determine if treatment improved over time
• can acts as surrogates for incidence rate

Question 2

what is the mortality (death) rate?

Answer 2

• consideres the number of deaths in a given time in the numerator and a denominator that includes all the population in that time period

= (all the deaths) / (total population at risk of dying)

Question 3

what is cause-specific death rate?

Answer 3

• focuses on the sub-group of the population that died from a specific cause of death

= (# of deaths from a specific cause in the time period) / (population from which death occurred in time period)

Question 4

what is case-fatality rate?

Answer 4

• the percentage of persons with a disease who die from the disease within a specified time period
• • more accurately described as a risk or percentage
• • measures severity

= (# of deaths among persons during a timed period after disease onset or diagnosis) / (# of persons with the disease) x 100

all cause > cause specific > case fatality

Question 5

what is the infant mortality rate?

Answer 5

• assesses the risk of dying during the 1st year of life
• • global indicator of maternal and child health in population

= (# of deaths under age 1 year in time period) / (# of live births in time period)

Question 6

what are problems with mortality data?

Answer 6

• most information about death comes from death certificates
• • a lot of errors involved in death certificates because it is based on the physicians opinion
• quality of data can vary by region and country

Question 7

what are the 9 Bradford Hill Guidelines for Causality?

Answer 7

1. strength
2. consistency
3. specificity
4. temporality
5. biological gradient / dose response
6. biological plausibility
7. coherence
8. experiment
9. analogy

Question 8

Bradford Hill - strength

Answer 8

stronger associations (i.e those with larger magnitude) between exposure and outcome are more likely to be causal than weak ones
- ratio vs. difference

Question 9

Bradford Hill - consistency

Answer 9

the same association is observed in different study populations

Question 10

Bradford Hill - specificity

Answer 10

a given health outcome is cause by one exposure
- might not hold
- exposures can lead to multiple outcomes
- more aligned with infectious diseases

Question 11

Bradford Hill - temporality

Answer 11

the exposure must precede the health outcome in time
- exposure must come before outcome

Question 12

Bradford Hill - biological gradient / dose response

Answer 12

higher levels of exposure lead to an increased frequency of the health outcome
- more you’re exposed, more likely to get outcome

Question 13

Bradford Hill - biological plausibility

Answer 13

the association between the exposure and outcome supported by what is known about the biological mechanisms causing that health outcome
- important to look through literature / data

Question 14

Bradford Hill - coherence

Answer 14

requires that the association between the exposure and health outcome align with what is already known
- looking at research that already exists

Question 15

Bradford Hill - experiment

Answer 15

evidence drawn from experimental studies provides strong support of causal relationship

Question 16

Bradford Hill - analogy

Answer 16

when one causal relationship has been presumed, other similar relationships are more likely to also be causal

Question 17

what makes a factor a “cause”?

Answer 17

• association between exposure and disease
• exposure must precede the disease *
• exposure must product outcome
• exposure may be related to person-level or environmental-level traits
• exposures can be negative (leads to disease) or positive (help prevent disease)
  if an exposure is causal, then elimination or reduction of the exposure will reduce or eliminate the disease

Question 18

cause & effect: simple or complex

Answer 18

simple (infectious disease) - factor to disease

complex (chronic disease) factor to step 1 to step 2 to disease

Question 19

cause & effect: mediator

Answer 19

• a component that causes the disease from the effect of another factor (M has to be there for disease to occur)
• in the pathway

factor to M to disease

Question 20

cause & effect: moderator

Answer 20

• a component that affects the strength and/or direction of the association between the factor and the disease
• not in the pathway
• • Moderator influences the disease
• • disease can still occur if M is absent

        M factor to disease

Question 21

4 types of Causal Relationships

Answer 21

1. necessary & sufficient
2. necessary but not sufficient
3. sufficient, but not necessary
   4 neither sufficient nor necessary

Question 22

4 types of Causal Relationships: necessary v sufficient

Answer 22

necessary - if a factor is necessary, the disease will NOT develop without the factor

sufficient - if a factor is sufficient for producing disease, the disease ALWAYS develops in the presence of the factor

Question 23

4 types of Causal Relationships: necessary & sufficient

Answer 23

Factor A to disease
- rarely happens
- - A present, disease always occurs

Question 24

4 types of Causal Relationships: Necessary but not sufficient

Answer 24

Factor A + B + C to disease
- factors together = disease
- - 1 or 2 factors only does not equal disease

Question 25

4 types of Causal Relationships: Sufficient but not necessary

Answer 25

Factor A to disease Factor B to disease Factor C to disease Factor A + B + C to disease - they can all cause the disease by themselves

Question 26

4 types of Causal Relationships: Neither sufficient nor necessary

Answer 26

Factor A + B to disease Factor C + D to disease Factor E + F to disease Factor A + B + C + D + E + F to disease - most frequent for chronic disease - if they are alone they won't get disease - - in pairs = disease