Lecture 6 Flashcards
Study design 1 (20 cards)
In a cohort study, how is the study population defined?
Participants are selected based on exposure status (exposed vs unexposed), before the outcome occurs
What is the main requirement regarding the timing of exposure and outcome in cohort studies?
Exposure must be measured before the outcome develops (temporal relationship)
What types of variables must be measured in cohort studies?
Exposure (e.g., smoking, diet)
Outcome(s) (e.g., incidence of disease)
Confounders (e.g., age, sex, SES)
How are outcomes measured in cohort studies?
Through follow-up over time, using clinical records, registries, or repeated assessments
What are two major types of cohort studies?
Prospective cohort (followed into future)
Retrospective cohort (uses historical data)
What statistical measures are used in cohort study analysis?
Relative Risk (RR)
Incidence Rate Ratio (IRR)
Attributable Risk
What is an important strength of cohort studies in terms of causality?
They can establish temporality and measure incidence rates
Name a classical cohort study that established a link between smoking and lung cancer
The British Doctors Study by Doll and Hill (1951)
What was the study design of the Framingham Heart Study?
A prospective cohort study started in 1948 to investigate cardiovascular risk factors
In a case-control study, how are cases selected?
Based on the presence of the outcome or disease of interest (e.g., lung cancer)
How are controls selected in a case-control study?
From the same population as cases but without the disease
What is the role of matching in case-control studies?
To control for confounding variables by pairing cases and controls on key characteristics (e.g., age, sex)
What is the primary measure of association in case-control studies?
Odds Ratio (OR)
What is a key limitation of case-control studies regarding incidence?
Cannot directly measure incidence or risk because the outcome has already occurred
What bias is particularly problematic in case-control studies?
Recall bias (cases may remember exposures better than controls) and selection bias
What kind of analysis is typically used in case-control studies to adjust for confounders?
Logistic regression
Name a classical case-control study that linked smoking to lung cancer
Wynder and Graham (1950) or Doll and Hill’s case-control study (1950)
What was a major finding from the Doll and Hill (1950) case-control study?
Strong association between cigarette smoking and lung cancer
Why is matching not always appropriate in case-control studies?
Overmatching can remove real associations and make controls too similar to cases
What is the ideal source of controls in a case-control study?
Individuals from the same population that produced the cases, who would be cases if they developed the disease
