Survival Analysis Lag-time

[Sharon Nomusa]

I am doing a survival analysis (using cox proportional hazards) on registry data. Cohort entry is the date of the first prescription for each participant. My follow-up starts 1 year after study commencement (fixed date). The one year wait in start of follow-up is a lag-time to account for reverse causation and also ensure time to exposure (ensure that everyone in the cohort is a maintenance user of the drug). I would like to include this lag-time in my analysis to ensure that I don't get immortal-time bias. I thought I could account for this by treating it as a delayed-entry and stset the enter with the 1year date. Im not sure if this is logical though. Any help will be greatly appreciated.