Survival Analysis Flashcards
What is survival analysis a subset of?
Cohort study
Randomized clinical trial
Target population randomly assigned intervention/treatment or control and outcomes measured
Objectives of survival analysis (3)
- Estimate time to event for a group of individuals
- Compare time-to-event between two or more groups
- To assess the relationship of co-variables to time-to-event
Expected time-to-event =
1/incidence rate
Time-to-event
the time from entry into a study until a subject has a particular outcome
Censoring
Subjects are said to be censored if they are lost to follow up or drop out of the study, or if the study ends before they die or have an outcome of interest. They are counted as alive or disease-free for the time they were enrolled in the
study.
How can dropouts bias results?
If dropout is related to both outcome and treatment
Data structure of survival analysis
Two variable outcome, use chi squared testl ci=1 if had event; ci=0 if no event by time ti
Right censoring (T>t)
termination of the study, death due to cause that is not the event of interest, loss to follow up
Why is survival a good choice to measure?
It is what people care about, easy to measure (retrospective data)
Hazard function?
instantaneous incidence rate
Common functions to describe survival?
Exponential - hazard constant over time
Weibull - hazard function is increasing/decreasing over time
Hazard ratio
compares rate of event happening between two groups
Hazard
annual risk of dying
