29 Cancer Epidemiology Flashcards
What are the 2 FACTORS in cancer epidemiology?
Distribution (FREQUENCY)
Determinants (influencing factors)
Epidemiology is at what SCALE
Population scale
2 assumptions of cancer epidemiology
- Cancer is NOT random
2. Cancer has CAUSAL and therefore PREVENTATIVE factors
What is the general AIM in cancer epidemiology?
Find ASSOCIATION between a potential RISK FACTOR and CANCER
What are the 2 MEASURES of frequency?
Define
Incidence = number of NEW CASES in a popn, within a TIME frame Prevalence = TOTAL number of cases in a popn, at a given TIME
What are 3 CONSIDERATIONS when calculating incidence?
- NORMALISE to allow comparison of popns
- Incidence rate PER PERSON TIME
- AGE-STANDARDISING of incidence rate
How can we NORMALISE the incidence rate?
Divide by total number of people
What is incidence rate PER PERSON TIME
Accounts for how long individuals were AVAILABLE TO RESEARCHERS
(populations are NOT STATIC)
Why does incidence rate need to be AGE-standardised?
Cancer increases with age
What is a consideration for PREVALENCE measures?
DURATION of disease
- CHRONIC = higher prevalence at given time
- ACUTE/good CURE = lower prevalence
2 CLASSES of epidemiological studies
What is the difference?
Experimental = INTERVENTION by investigator Observational = NO intervention (find groups already exposed)
Purpose of an EXAMPLE of experimental studies
Randomised clinical trials can evaluate:
- Effectiveness
- Side effects
2 sub-groups of observational studies
What is the difference?
Analytical = CONTROL present Descriptive = NO control group
3 types of ANALYTICAL-observational studies
CCE
- Cohort
- Case-control
- Ecological
The 3 types of ANALYTICAL-observational studies differ in what ASPECT?
DIRECTION of study
What is the DIRECTION of a cohort vs case-control study?
Cohort
= Exposure to Outcome
Case-control
= Outcome to Exposure
Give examples of COHORT vs CASE-CONTROL studies
Cohort = diet questionnaire about FAT intake, THEN determine cancer incidence (exposure to outcome)
Case-control = diet questionnaire for BREAST CANCER patients, see if they have fat intake differences (outcome to exposure)
Disadvantages of COHORT-analytical studies?
- needs MANY participants
- Lengthy = EXPENSIVE
- Unexpected CONFOUNDS
- Loss of FOLLOW-UP
COHORT-analytical studies are NOT SUITED for what kinds of dieases?
Diseases with
- Long-latency (eg. Cancer)
- RARE incidence
ADVANTAGES of cohort-analytical studies
- TEMPORAL relationships can be studied
- RELATIVE RISK can be calculated ACCURATELY
- MULTIPLE STUDIES can be done with same data
Advantages of CASE-CONTROL analytical studies
*No need for many aprticipants
*No need to WAIT for disease development
= quicker, cheaper, easier
Case control studies are SUITED FOR what kinds of dieases
Long-latency
Rare
DISADVANTAGES of CASE-CONTROL analytical studies
Selection bias = how cases/controls are CHOSEN
Recall bias = cancer patients more sensitive to exposures
= wording of questions
What are the 2 statistical measures of OUTCOME
What STUDIES are they used for?
Relative Risk = Cohort studies
Odds Ratio = Case-control studies
How is RR calculated?
Risk of disease WITH exposure/WITHOUT exposure
What does a RR mean if it is…
<1
=1
>1
RR<1 means ⬇️risk 😄
RR=1 means NO ∆risk
RR>1 means ⬆️risk 😩
What is an ECOLOGICAL study?
At least 1 variable measured at GROUP level
GROUPS in ecological studies are often DEFINED by…
Geographical boundaries (COUNTRIES)
Advantages of ecological studies
- Quick, cheap, easy
- Use ROUTINELY COLLECTED data
- Provide NEW hypotheses about causes
- Suggest NEW risk factors
Disadvantages of ecological studies
- Rely on AVG values
- ERRORS in recording quality
- Quality of HEALTHCARE varies
- POLITICAL influences
Name a type of DESCRIPTIVE study
Case reports - purely descriptive, NO CTRL
3 types of ERROR in epidemiological studies
Bias
Chance
Confounds
Explain BIAS
Systematic error
= NOT REPRESENTATIVE of true relationship
Explain CHANCE
RANDOM error
= unpredictable (due to protocol OR random nature of disease)
How can CHANCE be TESTED for?
Use P-value to test whether the result is STATISTICALLY SIGNIFICANT
What is a CONFOUND
CONFUSES the observation
3 criteria for something being a CONFOUND
- Is a RISK FACTOR for the disease
- Is ASSOCIATED with the exposure of interest
- Is NOT an INTERMEDIATE in a causal pathway
