cohort studies Flashcards
What are the features of cohort studies?
Observational, analytical
Selects a group without the outcome and follows them based on exposure
Prospective or retrospective
Used for common or rare exposures
Comparison of groups is essential
Outcomes must be measured consistently
What are the uses of cohort studies?
Investigate lifestyle factors and diseases (e.g., Framingham Heart study)
Study causes of infectious diseases based on exposure
Occupational health research
Prognostic studies on the association between exposure and survival/disease
What are the key analysis methods in cohort studies?
Disease frequency measures (incidence rate, risk, odds, mean, median)
Measure of effect (relative risk, odds ratio, absolute rate/risk, odds difference, vaccine efficacy, difference in mean/median)
Survival analysis
What are the advantages of cohort studies?
Can establish causality and show dose-response relationships
Suitable for rare exposures
Allows measuring multiple outcomes of a single exposure
Selection bias is minimized
Useful for diseases with long latency
Can measure incidence and prevalence
What are the disadvantages of cohort studies?
Time-consuming and expensive
Risk of loss to follow-up, affecting validity
Less effective for rare diseases
Potential for inadequate records in retrospective cohorts (information bias)
Healthy worker effect
Risk of misclassification of exposure or outcome
Changes over time in exposure or diagnostic criteria
Difficulty ensuring unexposed remain unexposed
What aspects should be considered in the critical appraisal of cohort studies?
Type of study and subject, journal, data, authors, conflicts of interest, funding, ethics
Clearly focused question using PICO
Population and setting, exclusion criteria
What elements of internal validity should be assessed in cohort studies?
Appropriateness of design, measurements (subjective/objective, validated, reliable)
Sample size, allocation, recruitment, loss to follow-up, selection bias
Clarity, validity, and reliability of exposure and outcome measurements
Appropriate statistical analysis, consideration of confounding factors
What considerations are important in assessing external validity of cohort studies?
Based on population, setting, and internal validity
Similarity of study participants to the target population
What aspects should be examined in the discussion section of cohort studies?
Limitations, justification of conclusions
What factors determine the relevance of cohort study findings to public health practice?
Applicability to public health practice, need for additional evidence, reproducibility considerations
