Evidence-appraisal glossary
Cox Proportional-Hazards Model
A widely used regression method for time-to-event data that estimates how much each factor multiplies the rate of an event, without assuming a particular shape for the underlying risk over time. Its main output is the hazard ratio.
Also called: Cox model, Cox regression, proportional-hazards regression.
The Cox model links survival outcomes to predictors such as treatment, age, or disease stage while leaving the baseline hazard unspecified, which is why it is called semiparametric. That flexibility made it the default tool for adjusted survival analysis across medicine. Its central assumption is that the hazard ratio between groups stays constant over follow-up, so when that fails a single summary ratio can mislead. Readers should check whether investigators tested this assumption before trusting one reported ratio.
This is a plain-language methodology definition for reading research. It is general education, not medical advice.