Risk factors, causality. Bradfordhill criteria. measurement of disease & exposure. Risk assessment

Question 1

define risk

Answer 1

risk refers to the probability an event will occur.

in epidemiology: probability a person exposed to certain factors will subsequently develop a particular disease

Risk factors: characteristics associated w/ increased risk of developing a disease or other health related event

Question 2

what is causality

Answer 2

an assumption that certains event cause/ produce subsequent events

a cause is:

1. associated w/ it’s effect
2. present before or simultaneously w/ it’s effect
3. acts on it’s effet

Question 3

interaction of events

Answer 3

• Not associated/ independent events: (A←//→B)
• Associated events (statistically): (A⇔B)
  
  • non causally associated /paralellism (↑A= ↑B)
  • Causally assoc directly (A→B)
  • Causally assoc INdirectly (A→C→B)

Question 4

Possible interactions between factor A and event B

Answer 4

• Factor A is NECESSARY & SUFFICIENT(A→B)
  
  • Monogenic disorder
• FACTOR A is NECESSARY but NOT SUFFICIENT(A+C→B)
  
  • TB, hpv.
• FACTOR A is NOT NESS but SUFFICIEENT (A→B, C →B)
  
  • Other risk factors involved. Cancer
• FACTOR A is NOT NESS & NOT SUFFICIENT (C±A →B)
  
  • Habits for DM patient.

Question 5

what is a confounding factor

Answer 5

Confounding factors occurs when an apparent association between a presumed cause and an outcome is accounted for by a third variable which is the confounder. This factor must be associated with both the cause and the outcome

• increase the probability of the event occuring
• age and sex are always confounding factors

Question 6

What is the Bradford Hill Criiteria

Answer 6

• a basis for causality assesment in epidemiology for an association to be causal it must meet as many criteria as possible
• published in 1965

1. Strength of association: the stronger the association more likely it’s causes
2. Consistency: replication of findings by diff investigators, times, places and methods. must explain dx in results
3. Specificity: the more specific the disease & exposure is defined the stronger the correlation
4. Temporality: cause should precede the effect only essential criteria
5. Biological gradient: change in exposure leads to a corresponding change in disease rates
6. Plausibility: association is consistant with current knowledge and beliefs
7. Coherance: observations must fit the hypothesized model to form a cohernat picture
8. Experiment: change in exposure must cause a change in the outcome in controlled conditons
9. Analogy: association may resemble similar events

Question 7

measurements of diseases and exposure and risk assesment

Answer 7

risk assesment

• Quantitative measures of the magnitude of the causal relationship between the risk factors and disease exist.
• uses relative risk, attributable risk and odds ratio

definition of relative risk(IE/INE)

• the ratio of the incidence in the exposed group (IE) compared to the incidence in the unexposed group(INE)
• used in cohort studies and epidemiological studies
• measures the amount of times the risk of diseas is in the two groups
• VAULUES
  
  • rr=1= no risk factor
  • rr<1 protective
  • rr>1 firsk factor

attributable risk

• the difference betw/ the incidence in the exposed and non exposed groups
• also used on cohort ration
• measures absolute risk

odds ratio

• relationship of probability of an event occurring vs the non occurence of the event

Question 8

ratio. proportion. rate

Answer 8

ratio

quantitative measure of the occurence of 2 independent events that may not have the same denominator

proportion

measuring the number of specifc events out of total

rate

occurence of an event in a population over time

case fatality ration

the cases of fatalities of a disease out of all the people with the same disease