Cohort Studies Flashcards
Is a cohort study an interventional or observational study
Observational
How is a cohort study carried out
Cohort identified -> exposure in each individual measured -> follow up to determine occurrence -> relate occurrence and exposure info
What can cause boas in case control studies
Loss to follow up if caused by exposure/disease
Exposure could cause disease after followup
unrepresentative cohort
Cohort study disadvantages
Take long time
Need a lot of people
Expensive
Incidence
Number of new cases/deaths of a disease per 100000 per yr
How is relative risk calculated
Incidence in exposed pop/ incidence in unexposed pop
What does a p value of <0.001 show in a cohort study
Risk of identified disease increase being due to chance less than 1 in 1000
What number must the 95% CI for a difference in means exclude for the results to be statistically significant
0
What number must the 95% CI for relative risk exclude for the results to be statistically significant
1
Confounded
Factor associated with both the exposure and the disease
How can confounders be adjusted for
Stratification
Log binomial regression
Poisson regression
What does a Kaplan Meier curve plot
Proportion of people surviving without an event over time
When are subjects censored
Lost to follow up
Drop out of study
Study ends before they die/have outcome of interest
What does hazard ratio show
Risk of dying at any time point in 1 group compared to another
What does a hazard ratio of 0.73 show for group A vs group B
Ppl in group A have 27% lower mortality risk than group B at any time during follow up
