Hazard ratio (HR)

The hazard ratio compares the momentary risk of the event between two groups or per unit of a number. 1 means no difference, above 1 a higher hazard, below 1 a lower one. It comes from the Cox regression; the 95% CI is by Wald.

Example: HR = 0.58, 95% CI [0.41, 0.80]: for women the event occurs at any time with 0.58 times the hazard of men. The range does not include 1.

Caution: An HR is not a risk ratio: HR = 1.8 does not mean the event is 1.8 times as likely. It only holds if the hazards are proportional over time.