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Complex Samples Cox Regression
Log-Minus-Log Plot
Figure 22-53
Log-minus-log plot
This plot displays the log-minus-log of the survival function, ln(−ln(suvival)), versus the survival
time. This particular plot displays a separate curve for each category of History of myocardial
infarct
ion,withHistory of ischemic stroke fixed at One and History of hemorrhagic stroke fixed at
None, and is a useful visualization of the effect of History of myocardial i nfarction on the survival
function. As seen in the parameter estimates table, it appears that the survival for patients with
one or n
o prior mi’s is distinguishable from the survival for patients w ith two prior mi’s, which in
turn is distinguishable from the survival for patients with three prior mi’s.
Summar
y
You hav
e fit a Cox regression model for post-stroke survival that estimates the effects of the
changing post-stroke patient history. This is just a beginning, as researchers would undoubtedly
want to include other potential predictors in the model. Moreover, in further analysis of this
datas
et you might consider more significant changes to the model structure. For example, the
current model assumes that the effect of a patient history-altering event can be quantified by a
multiplier to the baseline hazard. Instead, it may be reasonable to assume that the shape of the
base
line hazard is altered by the occurrence of a nondeath event. To accomplish this, you could
stratify the analysis based on Event index.