hazard ratio

Syllable breakdown

Dictionary meaning

a measure of the relative rate of an event occurring between two groups in a survival analysis — the ratio of the hazard rate in one group to the hazard rate in another at any given point in time; the hazard rate is the instantaneous rate of the event occurring given that it has not yet occurred — analogous to a continuous-time risk rate; the hazard ratio is the principal measure of association produced by Cox proportional hazards regression and is interpreted similarly to the relative risk — a hazard ratio of 2.0 means the event is happening at twice the rate in the exposed group relative to the unexposed group at any given time; the proportional hazards assumption — that the hazard ratio remains constant over the follow-up period — is a key model assumption that must be tested; hazard ratios are the standard effect measure reported in clinical trial survival analyses

Examples

• The hazard ratio for death in the immunotherapy arm was 0.68, indicating a 32 percent reduction in the instantaneous rate of death.
• The crossing survival curves indicated a violation of the proportional hazards assumption, making the hazard ratio an inadequate summary of the treatment effect.

Synonyms: HR