Understanding hazard ratios
A hazard ratio (HR) compares the rate of events in a treatment group to a control group. An HR of 1 means no difference. An HR less than 1 means the treatment reduces the hazard (beneficial); greater than 1 means the treatment increases the hazard (harmful).
The 95% confidence interval is computed using the log-normal method. If the interval does not include 1, the difference is statistically significant at the 5% level.
HR = (events_treatment / n_treatment) / (events_control / n_control)
Hazard ratio as the ratio of event rates.