Hazard Ratio

A hazard ratio (HR) compares the instantaneous rate (hazard) of an event occurring in one group versus another over a study's follow-up period. An HR of 1.0 means equal hazard; HR < 1.0 indicates a reduced event rate in the treatment group; HR > 1.0 indicates increased rate. Unlike odds ratios, hazard ratios account for the time dimension and censoring (participants who drop out or haven't experienced the event by study end). In supplement research, hazard ratios are used in long-term cohort studies and survival analyses examining endpoints like disease onset, mortality, or time to hair regrowth.