When reporting hazard ratios for Cox regression analysis, is it common to report the hazard ratio for the interaction term itself? For example, I have a model with 3 terms: a b a*b Using hazard ratio statements in SAS 9.4, I get a hazard ratio for 1) a at the mean of b, and 2) b at the mean of a. My understanding is that these hazard ratios are hazard ratios for the main effect variable (variable a or b) while holding the interacting variable constant. Is my understanding correct?   Is it possible to get a hazard ratio for the interaction term?   Thank you ... View more