HSPH PBL 5: Recreational Drug Use and Testis Cancer Risk Flashcards
What is a case-control study?
Start with a group of people with a disease (cases) and a group without the disease (control) and compare their past exposures to identify risk factors or causal factors
What is a cohort study?
Start with a group of people (cohort) and measure their exposures and follow them up to see who develops the disease
What are the advantages of case control studies over cohort studies?
Quicker, more practical if the outcome is rare, usually cheaper (less patients and quicker)
What are the disadvantages of case control studies?
May suffer from recall bias, different people are more likely to take part, can only study one outcome, may suffer from selection bias, cannot calculate absolute risks
What are the similarities between case control and cohort studies?
Both can suffer from confounding variables, both can consider multiple risk factors, can be done when RCT is unethical and are less accurate than a RCT.
Why can’t a clinical trial be used in this example?
It is unethical to test something that may be potentially harmful, let alone the ethics of giving people recreational drugs
How were the participants matched in this case control study?
By age, race, ethnicity and neighbourhood (important confounders)
Why was this study a case-control rather than a cohort study?
Case-control is more practical as the outcome is rare while some of the exposures are reasonably common, large number of risk factors were asked about for a reference period of 1 year prior to diagnosis, there is likely to be much recall bias as they were asked about risk factors just one year previously, quicker and cheaper (so earlier implementation can occur if the results warrant this).
What is an odds ratio?
The ratio of the chances of those with the disease (cases) being exposed to a risk factor compared with the chance of those without the disease (controls) being exposed.
What are crude/unadjusted/univariate results?
Tell us the relationship between one risk factor and the outcome for everyone in the study
What are crude results useful for?
Useful for identifying high risk groups of individuals
What are adjusted/multivariate results?
Tell us the effect we would get if we changed a risk factor if all the adjusting factors remain the same
What are adjusted results useful for?
More useful for investigating causality and deciding on what advice to give a patient or group of patients
What are confounders?
Factors that are associated with both the exposure of interest and the outcome
Do the results need to be adjusted?
In the study there doesn’t appear to be any association between cigarette smoking and testicular germ cell tumours and therefore cigarette smoking is nOT a confounder and he results therefore don’t need to be adjusted for it.
